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INTRODUCTION

An injury or response that results in any harm to a patient after medication administration is an adverse drug reaction (ADR). Every medication can potentially cause ADRs, but antibiotics are notorious for causing several individual and class-wide type reactions. A 2017 study (N = 1488) showed that 20% of all inpatients who receive antibiotics will develop an ADR within 24 hours of therapy. That risk increases by 3% every ten days of therapy.¹ Education and recognition of ADRs from antibiotics are essential components in the campaign against antibiotic resistance. The Centers for Disease Control and Prevention (CDC) developed the Core Elements of Antibiotic Stewardship to optimize antibiotic use by decreasing unnecessary antibiotic prescribing and helping fight antibiotic resistance in different practice settings. One Core Element is education directed at prescribers, nurses, pharmacists, and patients about the adverse reactions associated with antibiotic use.²

 

Antibiotic Resistance

One of the most noxious antibiotic-induced ADRs is the development of antibiotic resistance. Antibiotic resistance is a global health threat to the world population and affects food security.³ Antibiotic resistance develops when a bacteria is no longer susceptible to a previously effective antibiotic, which can stem from unnecessary antibiotic use.¹ A 2011 study that surveyed American acute care hospitals found that almost half of all inpatients will receive at least one day of antibiotic therapy.⁴ A separate U.S. study found that one-third of all antibiotic treatment days are inappropriate.⁵

 

Antibiotic resistance kills at least 1.27 million people worldwide every year.⁶ The United States (U.S.) has reported more than 2.8 million antimicrobial-resistance infections yearly, with 35,000 deaths.⁷ Antimicrobial resistance can affect anyone at any age, at all different types of healthcare facilities, and in veterinary and agricultural industries.⁶ Antibiotic resistance prevents patients from using first or second-line therapy for indicated infections, making patients more susceptible to severe ADRs.

 

Antibiotic Allergies

Allergic reactions reportedly account for 20% of adverse drug events and are seen in about 8% of the population.⁸ Antibiotics are the most common medication reported as an allergy.⁹ Elderly and female patients are more likely to report antibiotic allergies.^9,10 Typically, antibiotic allergic reactions present as mild rash and hives but approximately 3% of the population’s health records documented past anaphylaxis.¹¹

In the 1960s, Robert Coombs and Philip Gell established a classification system for hypersensitivity reactions. Coombs is most notable for developing the Coombs test that detects anti-Rh antibodies on red blood cells in 1945.¹² Their classification system has four presentations of hypersensitivity reactions involving different immune mediators that develop into various manifestations. Table 1 summarizes the Coombs classification.

Table 1 - Classification of Allergic Reactions13-15
Type	Description	Mechanism	Timing	Clinical features
I	IgE-mediated, immediate-type hypersensitivity	IgE serves to protect and eliminate parasitic infections. IgE antibodies form after exposure to allergens, such as food, drugs, or other environmental elements. Re-exposure triggers an immediate hypersensitivity reaction.	Minutes to hours after exposure	·     Anaphylaxis ·     Angioedema ·     Bronchospasm ·     Hives ·     Hypotension ·     Asthma ·     Allergic rhinitis
II	Antibody-dependent cytotoxicity	The drug binds to the surface of the cell. Antibodies then bind to the cell surface and are targeted for clearance by macrophages. Usually involves IgG or IgM	Appear 5-8 days after exposure but can take longer	·    Hemolytic anemia ·    Thrombocytopenia ·    Neutropenia
III	Immune complex disease	Soluble drug in bloodstream forms a complex with IgG or IgM. The immune complexes can activate complement and then deposits in various tissue like small blood vessels, joints, and renal glomeruli	One or more weeks to develop after drug exposure	·     Serum sickness ·     Arthralgias ·     Acute glomerulonephritis ·     Vasculitis
IV	Cell-mediated hypersensitivity	Stimulation of T cells	At least 48-72 hours, but can take days to weeks following exposure	·     Stevens-Johnson syndrome/ toxic epidermal necrolysis (SJS/TEN) ·     Drug rash with eosinophilia and systemic symptoms (DRESS) ·     Contact dermatitis

 

Antibiotic allergy reporting is essential to prevent patients from severe adverse effects, but it also comes with a risk. Prescribers overuse and overprescribe antibiotics. Overprescribing of antibiotics is associated with a higher incidence of new antibiotic allergies.⁹ In countries with low antibiotic usage, antibiotic allergies are less prevalent.⁹ Antibiotic overprescribing is especially notorious at urgent care facilities. A study showed that in patients presenting to urgent care for upper respiratory infections, healthcare providers prescribed antibiotics approximately twice as much as in emergency departments and nearly three times as much in primary care.¹⁶ This is concerning; nationwide, there are more than 10,000 urgent care facilities, and that number is growing.¹⁶

Inaccurate allergy documentation is another concern with antibiotic allergy reporting. Five percent to 15% of patients have documented penicillin allergies; however up to 90% of those patients can safely receive a penicillin antibiotic.^17,18 Antibiotic allergies prevent patients from receiving first-line therapy, which can increase health care costs, and increase the risk of treatment failures and adverse events.¹⁷ A study from 2003 showed that patients labeled with a penicillin allergy had a 63% greater cost for antibiotics than patients without a penicillin allergy.¹⁹

PAUSE AND PONDER: What are some individual antibiotics that make up penicillins and cephalosporins?

The best treatment for allergies is prevention. Before initiating any new antibiotic, the prescriber should obtain an allergy history. Pharmacists must review patients' profiles for allergies to beta-lactams and consider cross-reactivity. There is about a 2% risk of cross-sensitivity between penicillins and cephalosporins.¹⁷ Treatment for allergies depends on the type of reaction. Type I reactions are usually a medical emergency, and patients need immediate care. Antibiotic rechallenge is appropriate for patients with mild reactions like gastrointestinal distress or mild itching or rashes but should not occur for any patient who develops a severe reaction, like anaphylaxis, Stevens-Johnson syndrome, toxic epidermal necrolysis, or hemolytic anemia.¹⁰ Reactions that occur need documentation with sufficient detail, including medication used and time to reaction.¹⁷

Antibiotic-Associated Diarrhea

A frequent adverse event associated with antibiotic use is diarrhea, defined as three or more loose stools in 24 hours.^20-22 Antibiotic-associated diarrhea reportedly occurs in 5% to 30% of patients while receiving or up to two months after receiving treatment.²³ Antibiotic-associated diarrhea’s clinical presentation can range from mild diarrhea to pseudomembranous colitis.^23,24 Essentially all antibiotics can cause diarrhea, especially those that cover anaerobic microorganisms (organisms that grow without oxygen) like amoxicillin/clavulante, cephalosporins, and clindamycin.^21-23

Antibiotic-associated diarrhea can occur from multiple mechanisms. First, antibiotics disrupt normal microflora, allowinge overgrowth of microorganisms known to cause diarrhea.²³ Clostridium difficile (C. diff), which will be discussed later, is the most common of those pathogens. Other pathogens are Salmonella, C. perfringens type A, Staphylococcus aureus, and Candida albicans.^20,24 Antibiotics can directly affect the intestinal mucosa, independent of any antibiotic activity. For example, erythromycin stimulates a receptor that increases contractions in the stomach and small intestines, and clavulanate can activate small bowel motility.^20,24 Last, antibiotics can decrease normal fecal flora that breakdown carbohydrates and bile acids in the colon. The increase of carbohydrates and bile acid causes an influx of water into the colon, causing osmotic diarrhea.^20,24

Treatment of antibiotic-associated diarrhea depends on its severity. Mild to moderate disease treatment should focus on rehydration, discontinuation of the provoking antibiotic, or changing to a lower-risk antibiotic like quinolones, sulfamethoxazole/trimethoprim, or aminoglycosides, if appropriate.^22,23 Clinicians should order C. diff testing in patients with severe or persistent disease or any microbes mentioned above.²³

Probiotics are an alternative method to decrease antibiotic-associated diarrhea, but mixed evidence surrounds their use. A 2021 meta-analysis reviewed 82 randomized controlled trials and found a statistically significant association between probiotic administration and the reduction of antibiotic-associated diarrhea.²⁵ The results are difficult to translate to a specific recommendation as the meta-analysis included many randomized controlled trials that did not document the exact probiotics used. In addition, the study excluded antibiotics that are more likely to cause diarrhea and specific subsets of patients like geriatrics.²⁵ Probiotic use is low risk for most patients, but immunocompromised patients should use caution when considering therapy.^26,27 Probiotics are associated with rare secondary bacterial and fungal infections, which can be more prevalent in immunocompromised patients.^28-30 The most ideal way to prevent antibiotic-associated diarrhea is to limit antibiotic use.²

C. diff is a spore-forming bacteria that produces two separate exotoxins, A and B, that cause mucosal damage and inflammation.^22,23 Patients with C. diff infection (CDI) account for 10% to 25% of antibiotic-associated diarrhea cases, but CDI causes the majority of pseudomembranous colitis associated with antibiotic therapy.^23,24 Patients with CDI typically present with fever, lower abdominal pain, and cramping. CDI stool usually contains visible mucous and is foul-smelling.²² Significant risk factors include age older than 65, hospitalization, proton pump inhibitor use, and previous diagnosis of CDI.^22,24 Patients older than 60 have a much greater risk of developing CDI than patients aged 10 to 20 years.^24,31 Prescribers should consider C. diff testing after a patient has three or more unformed new or unexplained stools in 24 hours.¹²

Multiple diagnostic criteria confirm CDI. Lab results from CDI patients show elevated white blood cell count, decreased albumin, and fecal leukocytes.²⁴ Imaging with a CT scan can show inflammation and thickening of the colon, but it is not specific to CDI.²⁴ The Gold Standard testing for CDI is to test for toxins A and B with polymerase chain reaction (PCR) tests, but patients need to have unformed stool (bowel movement that is watery or soft) for this test. Patients with solid-formed stools do not have diarrhea and therefore do not have CDI, so testing is not warranted. Enzyme immunoassay (EIA) is another option that produces results much faster than the PCR test but has much lower sensitivity.^22,32

Providers should start treatment for C. diff after a positive test or before positive testing if a strong clinical suspicion exists.^24,32 Clinical guidelines do not recommend routine testing of C. diff in asymptomatic patients as C. diff colonization frequently occurs, especially in hospitalized patients and residents of long-term care facilities.³² Severity of disease, initial or recurrent occurrence, and other risk factors determine treatment. Disease severity can be non-severe, severe, or fulminant. In severe illness, the patient will have leukocytosis with a white blood cell count (WBC) of at least 15,000 cells/mL and a serum creatinine (Scr) level higher than 1.5 mg/dL. In non-severe disease, WBC and Scr levels are less than that of severe. Fulminant severity presents with hypotension or shock, ileus (an obstruction of the intestines), or megacolon (abnormal widening of the colon that is not caused by an obstruction).¹² Vancomycin and metronidazole have been the mainstay of treatment for more than 30 years until the development of newer medications. Fidaxomicin and bezlotuxumab are newer agents recently added to the Infectious Disease Society of America (IDSA) guidelines for CDI treatment.³³ Refer to 2021 IDSA guidelines for specific treatment recommendations.

Antibiotic-Induced Kidney Injury

Medications cause an estimated 20% to 40% of cases of acute kidney injury, with that estimation reaching almost 60% in the elderly population.^34,35 Antibiotics are a well-known cause of medication-induced renal dysfunction. Antimicrobials cause kidney dysfunction through tubular injury, severe tubular necrosis with cellular death, intratubular obstruction from crystal formation, and other mechanisms.³⁴ The direct cause is increased drug concentration, decreased excretion, and genetic differences predisposing some individuals to increased cell death or mitochondrial injury after exposure to certain antibiotics. In addition, patients with underlying kidney disease, acid-base disorders, and dehydration are at a greater risk of crystal formation with antibiotics that are insoluble in urine.^34,36 Most classes of antibiotics have varying degrees of risk for the development of renal dysfunction, but it is most commonly associated with aminoglycosides, beta-lactams, and vancomycin.^34,37

Renal dysfunction will develop in 10% to 25% of patients on aminoglycosides.^34,38 Symptoms of renal dysfunction develop five to seven days after initiation of therapy and will take up to 20 days for complete recovery after discontinuation of the aminoglycoside.^34,38 The risk for AKI increases in patients with longer therapy durations, exposure to concomitant nephrotoxins, and other comorbidities like chronic kidney disease.³⁸ Patients on aminoglycosides most commonly develop renal toxicity in the proximal tubule. Gentamicin has the highest potential to cause nephrotoxicity, followed by tobramycin and amikacin. Clinical practice has moved away from using neomycin systemically as it has an increased risk of causing nephrotoxicity, neurotoxicity, and ototoxicity.³⁴

Beta-lactams have a high risk of causing renal dysfunction, with carbapenems causing more renal toxicity than penicillins or cephalosporins.³⁴ Beta-lactams cause a wide range of renal toxicity, including acute glomerulonephritis, acute tubular necrosis, and acute interstitial nephritis.^34,39 Prolonged infusions of beta-lactams possess a similar risk of AKI compared to intermittent infusions.³⁹

Vancomycin’s incidence of nephrotoxicity is between 5% and 43%.^38,37,40 Vancomycin nephrotoxicity was initially associated with manufacturing impurities, but new manufacturing methods have eliminated this cause.^41-43 Onset occurs four to eight days after initiation of vancomycin and improves after discontinuation.^34,43 The overall pathophysiology of vancomycin-induced AKI is poorly understood as several mechanisms most likely contribute. Most patients who develop AKI on vancomycin do not undergo renal biopsies, and it is commonly prescribed with other nephrotoxic agents, which hinders a conclusive diagnosis.^34,38,43 Patients with pre-existing kidney disease, severe illness, a combination of nephrotoxic agents, obesity, and daily cumulative doses greater than four grams are at a higher risk of AKI.^34,41,44 Adjusting the vancomycin dose based on weight, levels, and renal function can help decrease the risk of kidney injury.³⁴ Pharmacists monitor vancomycin levels as trough and peaks which are low and high measurements of the actual medication in the patient.

Evidence of the risk of nephrotoxicity from the combination of vancomycin and piperacillin/tazobactam (VPT) has been conflicting.   Previous evidence has shown VPT to carry a two to three-fold higher risk than vancomycin alone, but this is unclear due to piperacillin/tazobactam being a pseudo-nephrotoxin.^42,45 Prescribing information states that piperacillin/tazobactam can increase serum creatinine causing a pseudo-nephrotoxicity.⁴⁶ Most studies that reported increased risk of nephrotoxicity used increased creatinine as an indicator of acute kidney injury (AKI). ^45,47 A 2022 study looked at levels of cystatin C (a biomarker used to test kidney function) and found no significant change in its value for patients on VPT.  Further, it also showed VPT combination did not lead to higher rates of dialysis or death.⁴⁸ Most recently in 2023, Chen et al. looked retrospectively at 35,644 patients receiving either VPT, vancomycin plus meropenem, or vancomycin plus cefepime.  This study found that the combination of VPT has a greater risk of AKI, dialysis, and mortality in patients receiving treatment for greater than 48 hours.⁴⁹ At this time, available research on the VPT combination’s nephrotoxicity is conflicting. Clinicians should exercise caution when using VPT and consider other therapies in patients at high risk of renal dysfunction, especially if the combination will continue for longer durations.

Overall, antibiotics pose a significant risk to renal function, so the clinical team must assess risk factors of age and co-morbid conditions before initiating therapy.³⁴ A few ways to prevent the development of AKI are^34,38

• dosages adjusted based on creatinine clearance and glomerular filtration rate (GFR)
• changing the dose based on trough or random levels
• adequate hydration, especially when using agents that form crystals in the urine
• avoiding concomitant nephrotoxins (i.e., NSAIDs, contrast, etc.) and
• regular monitoring of kidney function for long-term antibiotic use or when a patient has known risk factors for developing kidney dysfunction.

Clinicians must always practice good antimicrobial stewardship by prescribing shorter therapy courses to lower nephrotoxic agent exposure to the kidneys.³⁴

Sulfamethoxazole/Trimethoprim-Induced Hyperkalemia

The early 1980s through 1990s saw a significant rise worldwide of the human immunodeficiency virus (HIV) which also coincided with the first reported cases of hyperkalemia (high potassium levels) from sulfamethoxazole/trimethoprim (SMX/TMP). The CDC published a report in Morbidity and Mortality Weekly Report (MMWR) in June of 1981 describing the incidence of Pneumocystis carinii pneumonia (PCP; now known as Pneumocystis jirovecii), in five previously healthy young men.⁵⁰ This CDC report documents the first known cases of HIV. Before the discovery of HIV, P. jirovecii was a disease associated with malnourished and immunocompromised patients. Premature and malnourished infants often contracted P. jirovecii during World War II, and patients with hematologic malignancies in later years.⁵¹ Dr. Walter Hughes, known for his research with P. jirovecii, first recommended SMX/TMP for prophylaxis in 1977 and then for treatment in 1989.^52-54 Emerging cases of hyperkalemia associated with SMX/TMP usage increased significantly at the start of the HIV epidemic as P. jirovecii treatment requires high doses and HIV patients are prone to the development of hyperkalemia.^55,56

SMX/TMP causes hyperkalemia because trimethoprim is structurally similar to the potassium-sparing diuretics amiloride and triamterene.^55,57 Trimethoprim blocks channels that excrete potassium into the urine, causing a potential 40% reduction of urinary potassium excretion.^58,59 Inhibition of urinary potassium excretion also decreases potassium in the urine.^55,58 Hyperkalemia will subside after discontinuation of trimethoprim.⁵⁸

Although SMX/TMP-induced hyperkalemia is low risk for most outpatients, it is essential to recognize risk factors and drug interactions because hyperkalemia is a medical emergency if untreated.⁶⁰ Trimethoprim is excreted in the kidneys and will accumulate during acute and chronic kidney disease, which can increase the risk of hyperkalemia.⁶¹ Chronic kidney disease increases potassium levels, making it the most critical factor to consider when assessing risk for hyperkalemia.^57,62 Age greater than 65 and dose of greater than 20 mg/kg of trimethoprim for longer than a week also increases risk.^57,58

Risk assessment should include a review of any disease states or concomitant medications that could cause hyperkalemia (see Table 2). Studies have examined spironolactone’s effect when taken concurrently with SMX/TMP. A 2011 Canadian study examined patients receiving spironolactone and SMX/TMP prescriptions over 18 years. The study found that elderly patients treated with both medications had a 12-fold increased risk of hospital admission.⁶³ A 2015 Canadian study over 17 years looked at 206,319 patients to find an association between sudden death for patients taking spironolactone and antibiotics. Patients taking SMX/TMP were twice as likely to suffer from sudden death when compared to amoxicillin.⁵⁹

Table 2. Alternate Causes of Increased Risk of Hyperkalemia 57,60,62
Disease States	Medications
Renal insufficiency	NSAIDs
AIDS patients	ACE/ARBs
Diabetes Mellitus	Direct Renin Inhibitors
Congestive Heart Failure	Beta-blockers
Metabolic Acidosis	Heparin
Congenital Adrenal Hyperplasia	Digoxin
Hypoaldosteronisim & Pseudohypoaldosteronism	Cyclosporine and tacrolimus
	Pentamidine
	Potassium-sparing Diuretics

 

Prevention of hyperkalemia from SMX/TMP should include decreasing the dose in patients with impaired renal function. SMX/TMP is contraindicated in patients with severe hepatic damage and severe renal disease if the patient does not have monitoring of renal function and electrolytes.^57,61 If hyperkalemia develops, prescribers should discontinue SMX/TMP and treat hyperkalemia following guideline recommendations.⁵⁸

Daptomycin-Induced Eosinophilic Pneumonia

The FDA approved daptomycin, a lipopeptide antibiotic, in 2003. Providers use it to treat complicated infections due to methicillin-resistant staph and vancomycin-resistant enterococci. Daptomycin has been an effective treatment alternative for patients who cannot use vancomycin due to intolerance or drug resistance.⁶⁴ Daptomycin’s approved labeling lists eosinophilic pneumonia and myopathies as severe adverse events.

Eosinophilic pneumonia (EP) is a rare respiratory illness that can present with severe dyspnea, hypoxemia, and respiratory failure.^65-67 It is caused by eosinophil accumulation in the lungs as an acute or chronic process. Acute EP symptoms last less than one month and typically less than one week, while chronic presentation can take an average of five months before diagnosis.⁶⁸ Patients with acute EP present with a varying range in the presentation of symptoms. Some patients may have very mild symptoms and require no treatment, while some studies have shown much more severe manifestations, with more than 50% of patients requiring mechanical ventilation.^68,69 Patients typically present with a dry cough, chest pain, and fever.⁶⁸

EP develops when alveolar macrophages detect an antigen, which initiates an inflammatory process, eventually producing eosinophils and their subsequent migration to the lungs. Eosinophils are white blood cells that provide an essential defense against helminth parasites (worms). Reactions will develop in humans to presumably benign agents that incite a release of eosinophils.⁷⁰ In daptomycin-induced eosinophilic pneumonia, daptomycin is the inciting agent.

Accumulating eosinophils in the lungs or any tissue can cause significant damage.⁷¹ Eosinophils release toxic granule products like major basic protein and eosinophil peroxidase that can damage epithelial cells and nerves. They also release cytokines like transforming growth factors (TGF)-alpha and beta, which are associated with tissue remodeling and fibrosis.⁷¹ Alveolar macrophages, pulmonary endothelial cells, and airway smooth muscle cells also produce eotaxin, a potent chemoattractant of eosinophils.^65,72

EP’s primary causes are idiopathic.^68,72 Secondary reasons for EP are drugs or toxins and less commonly, parasitic or fungal infections.^68,72 The most frequently cited medications causing EP are daptomycin, mesalamine, sulfasalazine, and minocycline.⁶⁸ Daptomycin-induced EP was initially reported in 2007 after the drug’s approval.⁶⁵ Its pathophysiology is poorly understood. One proposed mechanism is that daptomycin may bind to human surfactant and accumulate in the alveolar space causing injury to the epithelium and subsequent eosinophil migration to the damaged tissue.^65,66,73 The second proposed mechanism is that daptomycin interacts with surfactant resulting in abnormal lipids. This contact induces an allergic reaction causing the release of several inflammatory markers and eventually shifts eosinophils into the respiratory tissue at least one week after the start of daptomycin therapy.^65,66,73

The Food and Drug Administration (FDA) has issued guidance for the diagnosis of daptomycin-induced EP with all of the following sequelae confirming a diagnosis of EP⁷⁴:

• Concurrent exposure to daptomycin
• Fever
• Dyspnea with increasing oxygen demands requiring mechanical ventilation
• New infiltrates on chest X-ray or CT
• Bronchoalveolar lavage (BAL) with >25% eosinophils
• Clinical improvement with daptomycin withdrawal

Risk factors have not been well established for daptomycin-induced EP. A 2016 study that reviewed 43 cases in systematic literature found that most patients were male (83%) and elderly (mean age of 65 years old). The same study found that dose or duration was not a risk factor.⁶⁶ A 2020 review looked specifically for risk with daptomycin and EP and found no association with age and sex. It also did not find an increased risk with high treatment doses. The study found, however, that around 30% of patients had diabetes or renal impairment.⁷⁵

Discontinuation of daptomycin should occur after a probable or definitive diagnosis of daptomycin-induced EP. Patients can experience respiratory failure from EP and may require oxygen supplementation or mechanical ventilation. Treatment can include a steroid taper starting with methylprednisolone and converting to prednisone over two to six weeks if appropriate.^65,66

Daptomycin-Induced Myopathy

Skeletal muscle effects are a rare but serious adverse event associated with daptomycin use. This adverse event presents as muscle weakness and pain, typically preceded by creatine phosphokinase (CPK) elevations.⁷⁶ In clinical trials, up to 6.7% of patients had elevated CPK levels, and daptomycin-associated myopathy occurred in 2% to 14% of patients.^77,78 During early clinical trials in the 1990s, researchers used 12-hour dosing intervals, but adverse skeletal muscle effects prohibited the trials from continuing.⁷⁹ Trials eventually restarted when once-daily dosing in dogs showed a lower incidence of CPK elevations.⁸⁰ Dosing frequency has a more direct relationship on skeletal muscle than peak plasma concentrations, making once daily daptomycin safer to administer than twice daily.⁸⁰

 

Skeletal muscle releases CPK from cells after various circumstances, including infections, intramuscular injections, and intense physical activity.⁸¹ The effect of daptomycin on skeletal muscle is thought to be from the drug's mechanism of action. Daptomycin works by breaking down the cell wall of bacteria, creating an opening, and causing a release of intracellular ions. In skeletal muscle, daptomycin also opens the cell wall and causes a release of intracellular CPK.⁸² Less frequent administration of daptomycin decreases the likelihood of CPK release as it allows skeletal muscle cells more time to repair.⁸²

 

Patients on concurrent statin therapy or who are obese (BMI >30) are at an increased risk of developing myopathies.⁷⁸ Daptomycin-induced myopathy is more likely to be seen with elevated daptomycin trough levels, but testing trough levels is expensive. Monitoring recommendations include weekly CPK levels to prevent skeletal muscle adverse events. More frequent monitoring should occur in patients with risk factors.^64,76 Holding statins when appropriate can help prevent adverse events during daptomycin administration.⁷⁸ Adverse skeletal muscle effects are reversible upon discontinuation of daptomycin.⁷⁶ Clinicians should discontinue daptomycin when CPK levels are more than 2000 U/L in asymptomatic patients or patients with CPK levels greater than 1000 U/L in symptomatic patients with no other reasoning for myopathies.⁶⁴

 

QT Prolongation

Medications are the most common cause of QT prolongation.⁸³ Medications can block specific outward potassium channels (IKr channels) in the heart, leading to QT prolongation. The slowing of outward potassium increases the plateau phase of the action potential, and electrocardiograms show a longer QT interval.⁸⁴ When potassium remains in the heart, the heart is kept at a positive charge that can prolong the repolarization phase. During this time, an ectopic beat generated by the heart can lead to Torsades de Pointe (TdP), a very dangerous and sometimes fatal arrhythmia.⁸⁵ Antibiotics like fluoroquinolones (FQ) and macrolides block IKr channels and can cause QT prolongation, which can potentially cause harm in patients with risk factors.

Macrolides and FQs are the most widely prescribed drugs in the inpatient and outpatient setting.⁸³ Levofloxacin and erythromycin have been cited most frequently for prescriptions in critical care and outpatient settings that cause QT prolongation.^86,87 A 2003 study found that a single dose of FQ administered to healthy patients can significantly prolong the QT interval when compared to placebo. The study demonstrated that moxifloxacin caused the most notable change, followed by levofloxacin and ciprofloxacin.⁸⁸ Ciprofloxacin and levofloxacin have more case reports of TdP than other fluoroquinolones but have a lower risk of QT prolongation. Their widespread use plays a more significant role in the incidence of TdP than their actual risk of developing QT prolongation.⁸³

A study reviewed the FDA Adverse Event Reporting System for patients who developed TdP. One-half of reports included macrolide use with no other concurrent QT-prolonging medications.⁸⁹ Of all the reports, 53% involved erythromycin use, while clarithromycin and azithromycin were 36% and 11%, respectively; further, in all of the reports that included erythromycin, 49% used intravenous (IV) erythromycin.⁸⁹ Of note, IV erythromycin use accounts for much less than other dosage forms with ointment at 66.1% of all prescriptions in 2020, oral dosages at 29.8% and all other forms including IV at 4.1%.⁹⁰

PAUSE AND PONDER:  What medications can indirectly affect QT?

The risk of QT prolongation with antibiotics is difficult to assess as several factors can influence risk. Potassium channel blockade is concentration dependent; anything that increases the medication’s concentration will increase risk of QT prolongation.⁸³ Examples are rapid intravenous administration and impaired clearance through inhibition of hepatic metabolism.^83,91 Another important risk factor to consider is female sex, especially elderly females.^83,84,91,92 Female patients have consistently developed prolonged QT at a rate much higher than males and are more commonly prescribed medications that prolong the QT interval than males.⁸⁷ Older patients are more at risk for QT prolongation but are also more likely to have structural heart disease, drug interactions, and decreased drug clearance.⁹³ Risk assessments for QT prolongation should consider structural heart disease, subclinical long QT syndrome or genetic abnormalities, electrolyte abnormalities like hypokalemia and hypomagnesium, and patients with a family history of sudden death.^83,91,92 Pharmacists need to review concurrent medications for drug interactions that cause direct QT prolongation and medications that can affect QT indirectly, like diuretics, which can lead to electrolyte abnormalities.⁹²

For inpatients, baseline and subsequent electrocardiogram monitoring is an option for patients at high risk for QT prolongation, but it is too expensive to perform on every patient.⁹² Counseling for outpatients should include warning signs of arrhythmias like palpitations and near-syncope or syncope and other conditions that can affect potassium levels, like gastroenteritis or the addition of a diuretic.⁹² A risk assessment for QT prolongation is imperative for every patient started on a fluoroquinolone or macrolide.

 

Tendinopathy with Fluoroquinolones

In 1995, the FDA warned about the possibility of tendon rupture with fluoroquinolones.⁹⁴ Since then, several studies have looked at the risk of tendinopathies with FQ and found that they are associated with a two to four times increased risk of acute tendinopathy and tendon rupture. The risk is highest in the first month after drug exposure.^94,95 The Achilles tendon is most commonly involved as it is a weight-bearing tendon and more susceptible to injury, but any can occur in any tendon.^95-97

The mechanism of action of tendinopathy from fluoroquinolones needs to be better understood and may be multifactorial. One proposed mechanism is that fluoroquinolones increase substances known to cause tendons’ breakdown. In a study, matrix metalloproteinase (MMPs) increased after exposure to ciprofloxacin. MMPs cause collagen breakdown, which makes up 70% of tendons.⁹⁸ Another proposed mechanism is chelation. A study looked at connective tissue of magnesium-deficient dogs and found that the tissue had a similar damaged appearance to tissue treated with FQs. The study hypothesized that because FQs chelate with cations like magnesium, its effect on joints is similar to magnesium deficiency.⁹⁹

Patients are at a higher risk of developing tendinopathies with FQs if they are older than 60 years, transplant recipients, or on concurrent corticosteroid therapy.⁹⁴ Prescribers should avoid concurrent use of steroids and FQ as the risk of tendon rupture increases by 14-fold.⁹⁴ Treatment recommendations are discontinuing the offending agent and using supportive therapy like analgesia and physical therapy.⁹⁵ Approximately 90% of patients recover without surgery in one month, but 10% develop long-term adverse effects like difficulty walking, decreased mobility, and pain.⁹⁶

Cefepime-Induced Neurotoxicity

Cefepime is a 4^th generation cephalosporin available since 1997.¹⁰⁰ The package insert for cefepime warns against neurotoxicity, but it is a potential adverse effect with all beta-lactam antibiotics.¹⁰¹ Beta-lactams cause neurotoxicity because they antagonize the gamma-aminobutyric acid (GABA) receptor to varying degrees.¹⁰² Beta-lactams all have an affinity for GABA receptors because they are all structurally similar to GABA.^103,104 Cephalosporins, including cefepime, competitively inhibit the GABA receptor by binding directly to the receptor.^105,106

Cefepime-induced neurotoxicity (CIN) typically presents as encephalopathy, somnolence, agitation, confusion, and disorientation, while aphasia and hallucinations are less common.^107-109 Patients occasionally will develop convulsions or non-convulsive status epilepticus.¹¹⁰

The most significant risk factor for CIN is renal dysfunction.^100,104,108 When a patient with poor renal function receives cefepime, a higher concentration of unbound medication stays within the cerebrospinal fluid, causing symptoms when it enters the central nervous system.¹⁰⁸ A study of 42 patients with CIN found that 93% of patients with neurotoxicity had abnormal renal function, and 76% of the studied patients had their cefepime dose adjusted appropriately.¹⁰² A study has shown that CIN occurred despite dose reductions and even in dosages of 500 mg daily in patients with ESRD.¹¹¹

In addition to renal dysfunction, several other risk factors for CIN need review. Overdose or use of excessive dosages puts patients at risk for CIN, and it is much more likely to be seen in patients without appropriate dose adjustments.^108,109 Drug monitoring sometimes includes measurement of the medication in the blood called a peak (highest) and trough (lowest) levels. A study has associated CIN with high trough levels. The study showed neurotoxicity did not occur at troughs of less than 7.7 mg/L, while it always manifested at troughs at or exceeding 38.1 mg/L. The study’s author has suggested a trough of 7.5mg/L as a potential target.¹¹² Patients 65 and older are at risk because of pharmacokinetic changes.^100,113 Although age is a significant risk factor, CIN will occur in 25% of patients younger than 65.¹⁰⁰ Last, patients with underlying brain diseases like cerebrovascular accident, Korsakoff’s syndrome, small-vessel disease, Alzheimer’s disease, benign brain tumor, malignancy, or previous seizures are at risk for CIN.^108,114

Prescribers should discontinue cefepime in patients who develop suspected CIN.^100,108 It typically takes two to three days to resolve symptoms.^100,108 Providers can initiate dialysis in patients experiencing severe symptoms as it can rapidly decrease the concentration of cefepime.¹¹⁴ Medications that stimulate the GABA receptor, like benzodiazepines or barbiturates, are more effective than phenytoin in patients who develop seizures.¹⁰⁴ Last, switching antibiotics can sometimes resolve symptoms, but symptom prolongation can occur with other beta-lactams like piperacillin and meropenem. Consider alternative antibiotic classes in appropriate patients.¹⁰⁸

Linezolid-Induced Thrombocytopenia

Linezolid belongs to a class of medications called oxazolidinones. The discovery and investigation of oxazolidinones occurred in the late 1980s, but development did not continue due to severe adverse events in animals.¹¹⁵ In the 1990s, scientists from the Pharmaca Corporation derived linezolid from the oxazolidinones class, and the FDA approved its use in April 2000 after clinical safety testing.¹¹⁶ Linezolid has a considerable advantage for treating severe gram-positive infections as it is available intravenous (IV) but also has 100% oral bioavailability.¹¹⁷ Another advantage of linezolid is it’s relatively safe to use, with only 0.4% of patients experiencing severe adverse effects in phase 3 trials.¹¹⁵ Several case reports of adults experiencing varying types of myelosuppression, like anemia or pancytopenia, emerged following linezolid’s clinical approval, but thrombocytopenia (low platelets) is the most prevalent.¹¹⁵

Linezolid-induced thrombocytopenia (TP) takes approximately seven to 14 days before onset.^115,118 Reports of TP differ depending on geographical location or definition used.^118-120 TP typically takes around 14 days to develop because the platelet has a seven to ten day life cycle.¹¹⁵ Although studies have proposed several mechanisms, a definitive cause has yet to be established.¹²⁰

Patients with the following risk factors need monitoring for the development of thrombocytopenia^{115,118,121,120}:

• Prolonged treatment course greater than 14 days
• Underlying disease with a predisposition to hematologic abnormalities
• Renal dysfunction, CrCl less than 30 ml/min, and dialysis. Linezolid is not primarily cleared renally but metabolized into two compounds. These compounds are renally eliminated and can accumulate in patients with renal dysfunction and may play a role in the development of thrombocytopenia
• Chronic liver failure
• History of vancomycin use
• Low baseline platelet level of less than 200
• Low body weight–Linezolid dosing does not change for adults nor require renal or hepatic impairment adjustment. When body weight decreases and total mg/kg of linezolid increases, the risk of thrombocytopenia increases. A study found that daily mg/kg doses between 22-27 (body weight between 55-70 kg) had a 48% chance of developing thrombocytopenia versus 72% in dosages greater than 27 mg/kg (body weight less than or equal to 45kg).

Discontinuation of linezolid should occur for patients who develop thrombocytopenia or any myeloid cell abnormality while on therapy.¹¹⁵ Myelosuppression is reversible after discontinuation of linezolid. Patients actively receiving therapy should have weekly monitoring of complete blood count and renal function monitoring.¹²¹ Monitoring is essential in patients receiving treatment for longer than 14 days, have pre-existing myelosuppression, take concurrent medications that cause myelosuppression, or have received prior antibiotic therapy from a chronic infection.¹¹⁷

 

Reporting ADRs

Identifying ADRs as they occur is vital to comprehensive patient care, but reporting ADRs is equally essential. The FDA established MedWatch in 1993 as a tool for healthcare providers and consumers to voluntarily report ADRs. ADRs can be reported through MedWatch or directly to drug manufacturers, who then are required to report ADRs to the FDA. The FDA uses the reported ADRs to make up the Adverse Event Reporting System (AERS), a postmarketing surveillance database. The information entered into AERS helps identify trends that are useful in determining causes and preventing prospective events.^122,123

PAUSE AND PONDER: Why is it important to include so much information when reporting ADRs?

The FDA defines a serious Adverse Drug Event (ADE) as fatal, life-threatening, incites hospitalization or prolongation of existing admission, causes significant disability, or congenital disability or anomaly to the patient.¹²⁴ The FDA asks healthcare providers and manufacturers to report all serious ADEs. Healthcare providers, including pharmacists, should also report any non-serious unexpected ADEs. These reports are helpful, even if the reaction is not directly related to the drug, as the reports may help discover unidentified ADEs. Healthcare providers should submit as much information as possible that is relevant to the ADE.¹²² Table 3 includes essential information to include in ADE reporting.

Table 3. Key-Inclusions for High-Quality ADE Report125

·        Clear description of event or outcome, include time to onset of signs and symptoms;

·        Suspected and concurrent medications details: dose, lot number, schedule, dates, duration (Include non-prescription medications, dietary supplements, and any recently discontinued medications);

·        Patient characteristics, including demographics (e.g., age, sex, race), baseline medical condition prior to treatment, co-morbid conditions, medication allergies, relevant family history, other risk factors;

·        Documentation of diagnosis, including methods of making diagnosis;

·        Clinical course of event and outcome (e.g., death, hospitalization, treatment);

·        Relevant objective information (e.g., laboratory data) at baseline, during therapy, and after therapy;

·        Response to discontinuation of therapy and re-initiation if available;

·        Any other relevant information.

 

Conclusion

This continuing education activity discusses only a fraction of commonly experienced adverse drug reactions associated with antibiotics. It is not an exhaustive list, but it provides valuable guidance for healthcare providers for antibiotics with established reactions and serves as a reminder to report any serious or atypical reactions that may occur while using new antibiotics.

Antibiotic-associated adverse drug reactions are a significant concern in healthcare. These reactions occur when antibiotics lead to unintended harmful effects, such as allergic reactions, organ damage, or antibiotic resistance. Inappropriate use or overuse of antibiotics increases risk of adverse reactions. Decreased renal and hepatic function, elderly patients, and drug interactions are common risks of developing ADRs in antibiotics. Recognizing risks and following recommended monitoring can help prevent ADRs from occurring. Anyone directly involved in direct patient care should report suspected ADRs and educate patients on the impact of these events to ensure the safe and effective use of antibiotics.

 

 

 

 

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Introduction

 

Consuming natural substances to produce a desired effect on the body dates back thousands of years to ancient Egypt, Rome, China, and many other cultures. Records from early Mesopotamia include written formulas using many oils still in use today, including cedar, cypress, and licorice. Around 300 B.C., the Greek philosopher Theophrastus described the medicinal benefits of natural substances in his History of Plants. Throughout the centuries, many philosophers, scientists, and physicians continued collecting, combining, and documenting the use of natural products to treat different illnesses.¹

 

As the science of medicine developed, so did the science of pharmacology. Isolation of the active ingredients found in herbal substances lead to the development of synthetic compounds with similar properties. The first synthetic medication, chloral hydrate, derived from chloroform and discovered in the 1800s by German chemist Justus von Lieberg, is still in use today.²

 

Fast forward to modern day, and the interest and use of prescription medications, over-the-counter (OTC) products, and dietary supplements are at an all-time high. In 2020, consumers filled 6.3 billion prescriptions in the United States³ (U.S.) and purchased more than 6 billion OTC products.⁴ The dietary supplement market reached an unprecedented level in 2020 with a global spend of $61.2 billion. Experts predict it will reach $128.64 billion by 2028.⁵

 

The COVID-19 pandemic, caused by the SARS-CoV-2 acute respiratory coronavirus, significantly impacted our perception and approach to healthcare.⁶ More and more people use complementary and alternative approaches to healthcare than ever before.⁷ For example, sales of elderberry supplements more than doubled and zinc products quadrupled shortly after the pandemic's start.⁸

 

Pharmacists, widely recognized as drug information experts, and pharmacy technicians routinely field consumers' questions about dietary supplements. Many pharmacists lack the necessary knowledge or don't know where to look to answer these questions. Pharmacy schools educate future pharmacists on prescription and OTC medications with courses about nutrition and dietary supplementation, if offered, available as electives. This continuing education activity presents information about dietary supplements through a series of seven common pharmacy situations and lets learners in on seven secrets they can apply to their practices.

 

 

 

Situation: Continuing education is a professional requirement many pharmacists find tedious. Looking through the UCONN online CE library and seeing a new continuing education activity entitled ‘Seven Secrets of Patient Safety with Dietary Supplements,’ a pharmacist remarks to the pharmacy team, "What a waste, no one even takes dietary supplements."

 

Secret #1: Almost 60% of people in the United States used a dietary supplement in the last 30 days.^11,12

 

Dietary supplements crowd the aisles in drug stores, supermarkets, warehouse clubs, and even corner convenience stores. The sheer number of products is staggering. The Dietary Supplement Database (DSLD) is an online, searchable database developed by the Office of Dietary Supplements (ODS) at the National Institutes of Health (NIH). The database contains product labeling information on dietary supplements sold in the United States, including both on and off-market products. DSLD currently lists more than 140,000 labels.⁹

 

In the early 1960s, the National Center for Health Statistics began a program named the National Health and Nutrition Examination Survey (NHANES). NHANES is a continuous program focusing on various health and nutritional measurements and assesses adults' and children's health and nutritional status in the U.S.¹⁰ Scientific and technical journals publish the study results.

 

One section of the program assesses dietary supplement use among adults. Results from the 2017-2018 NHANES show that^11,12

• 57.6% of adults 20 years or older used a dietary supplement in the past 30 days
• Women (63.8%) had a higher utilization than men (50.8%)
• Use of dietary supplements increased with age, with women 60 years or older reporting the highest usage at 80.2%
• Use of multiple dietary supplements increased with age
• Most common dietary supplements used by all age groups include multivitamin-mineral supplements, vitamin D, and omega-3 fatty acids

 

The Council for Responsible Nutrition (CRN) is a trade association for the dietary supplement and functional food industry. Annually, the CRN performs a survey gathering data on consumer use of dietary supplements. The 2019 survey conducted by the CRN underscored dietary supplement usage with the following results¹³:

• 77% of US adults take dietary supplements, including 79% of American women and 74% of males
• Top reasons for taking supplements included:
  • Energy
  • Immune health
  • Filling nutrient gaps
  • Healthy aging
  • Heart health

 

The COVID-19 pandemic significantly impacted our perception and approach to healthcare.⁶ As of August 5, 2022, SARS-CoV-2 has infected more than 580 million people worldwide.¹⁴ Interest in boosting our overall immunity and protecting ourselves from viral infections has dramatically increased as a result.⁷ Many vitamins and minerals play essential roles in proper immune function.^7,15 Sales of supplements associated with boosting immunity increased over the last two years, including vitamins C and D, zinc, omega-3, garlic, ginger, and turmeric.¹⁶

 

Table 1. Common Dietary Supplements and Potential Uses^7,17,18

 

Dietary Supplement	Potential Use
Black Cohosh	Menopausal symptoms
Calcium	Dyspepsia Osteoporosis Premenstrual syndrome
Echinacea	Prevention and treatment of the common cold Promotion of wound healing
Elderberry	Prevention of upper respiratory tract infections Reduction in duration and severity of symptoms of the common cold
Folic acid	Folate deficiency Kidney failure Neural tube defects
Ginkgo	Anxiety Dementia Memory improvement Premenstrual syndrome
Ginger	Dysmenorrhea Nausea and vomiting Osteoarthritis
Ginseng	Cognitive function Erectile dysfunction
Iron	Anemia Restless leg syndrome
Magnesium	Constipation Dyspepsia
Melatonin	Sleep disorders
Multivitamin with minerals	General supplementation
Omega-3 fatty acids	Alzheimer’s disease Cardiovascular disease Dementia Depression Reduction of triglycerides
Potassium	Hypokalemia Hypertension Kidney stones
Probiotics	Atopic dermatitis Antibiotic-associated diarrhea Irritable bowel syndrome
St. John’s Wort	Anti-depressant Menopausal symptoms
Turmeric	Allergic rhinitis Osteoarthritis Pruritis
Valerian	Insomnia
Vitamin A	Aging skin Healthy vision
Vitamin B-12	Vitamin B-12 deficiency
Vitamin C	Anemia Antioxidant effects Prevention of the common cold Vitamin C deficiency
Vitamin D	Osteomalacia Osteoporosis Vitamin D deficiency
Vitamin E	Alzheimer's disease Dysmenorrhea Premenstrual syndrome
Zinc	Acne Depression Diabetes Diarrhea Treatment of common cold

 

 

Eating a healthy diet is essential for good health and nutrition. The Dietary Guidelines for Americans advise professionals, including policymakers, health care providers, and nutrition educators, about what to eat to meet the body’s nutritional needs. It emphasizes eating a diet rich in nutrient-dense foods, such as fruits and vegetables, as the best way to meet the body’s nutritional needs. The guideline identifies specific populations in which dietary supplementation may be necessary, such as women who are pregnant or lactating and adults older than 50.¹⁹

 

In addition to these defined special populations, many pharmacy patients may find it necessary to take specific vitamins or minerals due to medication-induced nutrient deficiencies.

 

Table 2. Examples of Nutrient Depletion Induced by Medications^7,17

 

Nutrient	Medication(s)	Mechanism
Vitamin D	Anticonvulsants	Increase hepatic metabolism
	Bile acid sequestrants	Decrease absorption
	Orlistat	Decrease absorption
Magnesium	Estrogens	Decrease serum levels by increasing uptake into tissues
	Loop diuretics	Increase excretion
	Proton pump inhibitors	Decrease absorption
Vitamin B12	Biguanides	Decrease absorption
	Proton pump inhibitors	Decrease absorption
	H-2 blockers	Decrease absorption
Potassium	Loop diuretics	Increase excretion
	Thiazide diuretics	Increase excretion
	Corticosteroids	Increase excretion

 

The pharmacist's dismissal of dietary supplement education is understandable. No one wants to waste precious time on irrelevant continuing education. However, the facts presented here illustrate the need for pharmacist education on dietary supplements.

Pause and ponder: A patient presents information about taking lemon and baking soda tea to prevent COVID-19 infection and asks you if it really works. How would you approach this conversation?

 

Situation: Sunday afternoons sometimes (but not often!) present the opportunity to catch up on administrative activities. While completing an inventory reconciliation of the vitamin section, a technician inquires, "Why does the FDA approve so many different products?" Looking up distractedly from the CII safe count, the pharmacist pauses, then replies in a weary voice, "You know, I’m not sure, probably just to make it more confusing for us."

 

Secret #2: Regulatory oversight of dietary supplements differs from prescription and OTC medications.

 

What is a Dietary Supplement?

 

On the most basic level, a dietary supplement is a substance consumed to add nutrients to a diet or to lower the risk of certain health problems. The use of natural substances has been around for millennia, but it is only within the last five decades that countries worldwide have formalized language and regulations around dietary supplements. Terminology, quality control, and safety assessment differ depending on the country and governing legislative body.²⁰

 

In 1994, the United States Congress passed the Dietary Supplement Health and Education Act (DSHEA), an amendment to the Food, Drug, and Cosmetic Act. DSHEA defines the term dietary supplement as a product intended for ingestion and containing an ingredient that supplements the diet. Dietary supplement labeling must include the term ‘dietary supplement’ or an equivalent term such as ‘herbal supplement’ or ‘magnesium supplement.’ DSHEA also stipulates that a dietary supplement must be free of contamination, adulteration, and properly labeled.²¹ We will discuss dietary supplement product integrity and labeling later in this activity.

 

According to DSHEA, dietary supplements include vitamins, minerals, herbs, other botanicals, amino acids, and live microbials (probiotics). Dietary supplements are available in many different formulations including tablets, capsules, soft gels, gel caps, powders, and liquids.²¹

 

DSHEA defined the term ‘new dietary ingredient’ as an ingredient that meets the above criteria and was unavailable in the U.S. before October 15, 1994. If manufacturers want to market a product containing a new dietary ingredient, they must notify the U.S. Food and Drug Administration (FDA) before marketing. The FDA then reviews the product for safety but not effectiveness.²¹

 

Regulation of Dietary Supplements

 

The FDA and the Federal Trade Commission (FTC) share regulation and oversight of dietary supplements. The FDA is responsible for the information provided on dietary supplement product labeling, including the package labeling, product inserts, and information available at the point of sale. The FTC monitors dietary supplement advertising, ensuring advertisements are truthful, substantiated, and not misleading. Both agencies have the authority to address violations and work together to ensure their efforts are consistent with one another.²²

 

The FDA does not have the authority to approve dietary supplement products before manufacturers market, distribute, and sell them to consumers. Manufacturers are responsible for ensuring the products they produce and distribute meet all quality standards defined by federal law. Quality standards include²²

• Ensuring the safety of the dietary ingredients used in the product
• Following current Good Manufacturing Practices (cGMP)
• Meeting all product labeling requirements
• Ensuring substantiation of all claims made about the product
• Ensuring products are free of adulteration or misbranding

 

cGMP, defined and regularly updated by the FDA, establish the minimum requirements for manufacturing, packaging, and labeling products to ensure product quality. cGMP includes guidance on obtaining quality ingredients, operating procedures, and quality controls.²³ Failure to follow cGMP results in possible product contamination.

 

While the FDA may not have the authority to approve dietary supplements before the product marketing and distribution, it can monitor products via post-marketing surveillance and auditing. The FDA routinely performs manufacturer inspections, monitors the marketplace, and investigates adverse event reports. Follow-up includes working with the manufacturer to bring the product into compliance, issuing warning letters, and recalling products.²¹

 

Reporting Issues with Dietary Supplements

 

Post-marketing surveillance is essential for documenting and monitoring any issues with dietary supplements. Information about severe reactions and product quality are important issues to report. The FDA Safety Reporting Portal is an online tool used to report safety issues on several categories of products, including pet or livestock foods, tobacco products, animal drugs, and dietary supplements.²⁴

 

The website address for the portal is https://safetyreporting.hhs.gov. Anyone can use the portal to report issues, including consumers, healthcare professionals, manufacturers, and researchers. Generating a new report starts on the home screen. The reporter chooses to file the report as a guest or by creating an account. Creating an account streamlines data entry and allows the reporting individual to save a draft of the report, follow up on a report, and view previous submissions.²⁴

 

Generation of an Individual Case Safety Report ID (ICSR) occurs after report submission. The ICSR allows the reporter to identify the report for future reference including submission of a follow-up report with additional information. FDA reviewers assess the seriousness of the reported issue and assign follow-up. Submission of this information allows the FDA to identify potentially dangerous products and potentially remove them from the market.²⁴

 

Traditionally, insurance companies limit coverage to prescription medications. Recent trends show an expansion of coverage to include some dietary supplements. Insurance coverage of dietary supplements blurs the regulatory differences between prescription medications and dietary supplements. Understanding the differences in oversight is beneficial and allows the pharmacy staff to counsel patients effectively.

Situation: While running back to the pharmacy after a much-needed bathroom break, a pharmacist stops when approached by a customer asking for advice about an iron supplement. Overhearing the inquiry, another customer comments, "You should buy that online; it’s cheaper, and the quality is just as good." The pharmacist nods assent, turns, and hurries back to the pharmacy amid the erupting sounds of chaos behind the counter.

 

Secret #3: Product integrity fluctuates between manufacturers and sources of dietary supplements.

 

Integrity of Dietary Supplements

 

The lack of government oversight opens the door for substandard products to flood the market. Poor ingredient quality, heavy metal or microbial contamination, adulteration, and mislabeling occur regularly. In the current economy, with rising prices, consumers are turning to less expensive options, and cheaper is not necessarily better, especially with dietary supplements.

 

In the literature, many studies exist that analyze dietary supplement product integrity. A study published in 2021 tested multiple bottles of 29 herbal supplements for consistency of ingredient activity and the presence of metal and fungal contaminants. The analysis showed inconsistent ingredient activity not only between bottles of the same product manufactured by the same company, but also between bottles manufactured by different companies. Assaying for metal contamination found zinc in 88% of bottles and nickel in 40% of bottles. In 37 of 58 bottles tested, fungal contamination was present, with 21 bottles having multiple strains.²⁵

 

Another study analyzed 41 dietary supplements for the presence of cadmium, lead, and mercury. Results revealed that 68.3% of samples contained contamination with cadmium and lead, and 29.3% with mercury.²⁶ One research team evaluated 121 dietary supplements along with 49 prescription drugs for levels of toxic element contamination. A small percentage of the dietary supplement products exceeded safety levels for mercury, lead, cadmium, arsenic, or aluminum. None of the prescription products exceeded these safety levels.²⁷

 

Adulterated products contain substances not listed on the product labeling, substitution of inferior materials for active ingredients, or may contain a lesser amount of ingredients. Weight loss, sports enhancement, and sexual function supplements commonly contain banned substances.²⁸

 

The FDA created and currently maintains the Health Fraud Product Database to increase awareness. This database contains information about products cited in warning letters, advisory letters, recalls, public notifications, and press announcements for various issues. Issues cited include products claiming to cure, treat, or prevent a disease and products containing undeclared ingredients or a new dietary ingredient.²⁹ The database is available in the consumer section of the FDA website at https://www.fda.gov/consumers/health-fraud-scams/health-fraud-product-database.

 

On January 2, 2022, the FDA issued a warning letter to the manufacturers of Nasitrol, a nasal spray based on the ingredient iota carrageenan. A review of the product’s website found claims that the product is intended to mitigate, prevent, treat, diagnose, or cure COVID-19 in people. Federal regulations define products making these claims as drugs and subject to review by the FDA before approval and subsequent marketing. As discussed earlier, this is in direct violation of federal regulations.³⁰

 

In another example, on July 15, 2022, the FDA issued a public notice advising consumers to refrain from purchasing Adam’s Secret Extra Strength Amazing Black, a product promoted for sexual enhancement. Laboratory analysis found that the product contained tadalafil, a prescription medication used for erectile dysfunction.³¹ Due to the potential for severe side effects such as hypotension, tadalafil administration requires medical supervision by a physician.³²

 

A study published in 2018 analyzed FDA warning letters issued from 2007 through 2016, using data from the Health Fraud Product Database. During this time frame, the FDA found 776 adulterated dietary supplements from 146 different companies. A total of 157 products contained more than one unapproved ingredient. Products marketed for sexual enhancement accounted for 45.5% of letters, weight loss 40.9%, and muscle building 11.9%. Unapproved ingredients included sildenafil in sexual enhancement, sibutramine in weight loss, and synthetic steroids or steroid-like ingredients in muscle building supplements.³³

 

One way for consumers to know they are purchasing a valid product is by looking for a certified product. The certification process involves an independent, third-party company testing a company’s products, offering quality assurance for dietary supplements. Parameters tested include³⁴

• Product contains the ingredients stated on the label
• Presence of harmful ingredients
• Presence of contamination
• Proper dissolution
• cGMP followed during manufacture

 

Three independent, private, third-party certifying organizations operate in the United States: the US Pharmacopeial Convention (USP), NSF International, and Consumerlabs.com. All three companies offer product certification programs for a fee. Each company allows products passing certification to display a seal on product labeling. Table 3 summarizes information about each organization.

 

Table 3. Dietary Supplement Certification Organizations

 

Certifying Organization	US Pharmacopeial Convention	NSF International	Consumerlab.com
Website	www.usp.org www.qualitysupplements.org	www.nsf.org	www.consumerlab.com
Services offered	Dietary supplement verification program including GMP facility audits, product QCM process evaluation, and product testing	Product and ingredient certification GMP Certification Certified for Sport	Product reviews Quality Certification Program
Information available on the website	Program information, list of verified products, and educational resources	Program information, product search engine, and educational resources	Product reviews, health condition information
GMP = Good Manufacturing Practice

Source: adapted from reference 33

 

Online product ordering is a convenient shopping option rapidly gaining popularity in recent years, especially during the pandemic. While tempting to order the least expensive product, investigating the source and quality of dietary supplements available online is essential. Proactive training of the entire pharmacy team aids in providing patients with accurate information.

Situation: A weary technician finally finishes ringing out the last customer after two hours straight at the register. A sigh of relief quickly turns into a disgruntled groan as another customer approaches. With a bottle labeled ‘Menopausal Support’ in hand, the customer points to the bottle label and asks, "What does ‘proprietary blend’ mean?" The technician glances over her shoulder, sees the pharmacist engaged in an intense phone conversation, and replies to the customer, "The bottle label clearly lists the ingredients."

 

Secret #4: Federal regulations define required dietary supplement label information. Unfortunately, ambiguity still exists, making it challenging to identify exactly what the product contains.

 

Federal regulations define the information required on dietary supplement product labeling in detailed, specific terms. Product labeling must include³⁵

• Product name
• The term ‘dietary supplement’ or similar term (i.e., herbal supplement)
• Name and location of the manufacturer, along with a domestic address and phone number for reporting serious adverse events
• Nutrition labeling in the form of a “Supplement Facts” panel with the following information (see Figure 1):
  • Serving size
  • Number of servings per container
  • Listing of each dietary ingredient in the product
  • Amount of dietary ingredient per serving (Exception: ingredients in a proprietary blend)
  • Amount per serving listed as a quantitative amount by weight, as a percentage of the Daily Value, or as both
• A list of other ingredients not declared on the Supplement Facts label (usually excipients such as preservatives or dyes)
• Net quantity of contents

Figure 1. Supplemental Facts Label (sourced from reference 36)

One area of ambiguity in dietary supplement product labeling is the listing of a proprietary blend. The term proprietary blend refers to a blend of dietary ingredients unique to a manufacturer and product. Federal labeling regulations allow the listing of proprietary blends on dietary supplement products, however, only the total weight of the blend is required, not the weight of individual ingredients.³⁵ There is no way for the healthcare professional or consumer to know exactly how much of a particular ingredient the proprietary blend contains.

 

Consumerlabs.com cautions consumers about products containing proprietary blends or formulas. In many instances, the blend's name sounds like a desired, expensive ingredient that is only a small part of the formula. Marketing of products containing proprietary blends may mislead the consumer with claims meant to impress the consumer and drive sales of the product.³⁷

 

FDA regulations do allow structure/function claims on dietary supplement labeling. Structure/function claims describe how a nutrient or dietary ingredient may affect or act to maintain the structure or function of the body.³⁵ Examples of structure/function claims include³⁵

• Calcium builds strong bones
• Antioxidants maintain cell integrity
• Fiber maintains bowel integrity

 

If a dietary supplement label contains a structure/function claim it must also contain the following statement: "This statement has not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease."³⁵

 

The example in this situation involved a product marketed for menopausal support. Menopausal symptoms affect more than 1 million women in the US annually and include symptoms such as hot flashes and sleep disturbances.³⁸ A search of the DSLD using the term ‘menopausal support’ and filtering for on-market products containing the ingredient ‘proprietary blend’ returned almost 3,000 products.⁹ This abundance of products illustrates the ambiguity that exists on dietary supplement labeling.

 

Pharmacy technicians are often the first line of contact at the pharmacy. Training and development of pharmacy technicians on the facts surrounding dietary supplements empower technicians, allowing them to answer factual questions and provide effective patient education.

 

Situation: The pharmacy phone constantly rings throughout the day, and today is no exception. The new COVID vaccine is out, and everyone wants to know if the pharmacy has it in stock. Answering yet another call, the technician is surprised when a patient asks to talk to the pharmacist, complaining about dizziness. The pharmacist checks the patient’s profile, finding no underlying causative medication. Further questioning the patient, the pharmacist uncovers the recent addition of melatonin at night for sleep.

 

Secret #5: Like prescription medications, dietary supplements have pharmacologic and physiologic effects on the body, potentially resulting in health risks and side effects.

 

Consumers perceive dietary supplements as safe due to their source from natural substances. While generally well tolerated, dietary supplements affect the body like prescription medications, capable of producing an undesired effect. Lack of regulatory oversight allows products to reach consumers without adequate safety evaluation.

 

Information describing adverse effects of dietary supplements is anecdotal, derived from case reports and reports submitted through the FDA Safety Reporting Portal. Most dietary supplements have not been studied in pregnant or lactating women or children.

 

A study published in 2015 evaluated ten years of emergency room data to assess the number of annual visits resulting from dietary supplement adverse events. The authors calculated an average of more than 23,000 emergency room visits stemmed from the consumption of dietary supplements, resulting in more than 2,000 hospitalizations annually.³⁹

 

Events in older adults accounted for the highest percentage of visits, with 40% of visits due to difficulty swallowing. Incidence in young adults aged 20 to 34 was significant at 28% and primarily involved weight loss and energy products. Side effects reported include heart palpitations, chest pain, and tachycardia.³⁹

 

Unsupervised child ingestions accounted for 21% of visits. Unlike prescription medications, regulations do not require child-resistant packaging for dietary supplements, except for iron-containing products.³⁹ The authors note the numbers evaluated in the study are likely underreported as patients do not always include dietary supplements with the current medication list.³⁹

 

Table 4. Adverse Effects of Common Dietary Supplements^7,17

 

Supplement	Adverse Effects
Black Cohosh	Breast tenderness, diarrhea, gastrointestinal upset, nausea/vomiting
Calcium	Burping, constipation, gastrointestinal upset
Echinacea	Diarrhea, constipation, gastrointestinal upset/pain, heartburn, nausea/vomiting, skin rashes
Ginseng	Gastrointestinal side effects, headache, sleep difficulty
Ginger	Burping, diarrhea, heartburn
Iron	Abdominal pain, constipation, diarrhea, nausea/vomiting
Magnesium	Diarrhea, gastrointestinal irritation, nausea/vomiting
Melatonin	Dizziness, drowsiness, headache
Omega-3 fatty acids	Bad breath, headache, heartburn, nausea, diarrhea, unpleasant taste
Potassium	Abdominal pain, burping, diarrhea, nausea/vomiting
St. John’s Wort	Diarrhea, dizziness, dry mouth, fatigue, headache, insomnia
Turmeric	Constipation, dyspepsia, gastrointestinal reflux, nausea/vomiting
Vitamin C	Abdominal cramping, heartburn, kidney stones (if history of kidney stones)
Zinc	Abdominal cramping, diarrhea, metallic taste, nausea/vomiting

 

 

Patients often fail to report usage of dietary supplements and most pharmacy software lacks the ability to note dietary supplement usage in the patient profile. In this situation, the pharmacist took the extra time to further question the patient about dietary supplement usage and successfully identified the causative agent.

 

Pause and Ponder: In what ways could you incorporate activities into the daily workflow to increase awareness of patients’ use of dietary supplements?

 

Situation: Today, the workload in the pharmacy is lighter than usual. With a grateful sigh, the pharmacist sinks onto a stool reaching for a quick snack. Then the phone rings… The caller is a triage nurse from the local hospital to verify a patient’s medication profile. Pulling up the profile, the pharmacist verifies the list of medications, including digoxin. The triage nurse confirms atrial fibrillation as the cause for admission, adding that the patient recently started taking St. John’s Wort for depression.

 

Secret #6: Some dietary supplements affect the CYP450 liver enzymes, potentially altering the pharmacokinetics of medications, leading to treatment failure and/or toxicity.

 

Dietary supplement-drug interactions

 

Drug-drug interactions result in altered absorption, metabolism, or excretion. Drug-dietary supplement interactions occur through the same pathways as those used by FDA-approved drugs. The cytochrome P450 (CYP P450) enzymes in the liver are responsible for the metabolism of most medications.^41,42 The ability of a drug to either induce or inhibit these enzymes is a significant factor in drug-drug interactions. The natural ingredients found in dietary supplements are capable of inhibition or induction, also having the potential to interact with medications.

 

St. John’s Wort, an herbal commonly taken for the relief of mild to moderate depression, induces the activity of CYP3A4.^43,44 This induction increases the clearance of medications metabolized by CYP3A4. Examples of medications cleared by CYP3A4 include alprazolam, atorvastatin, cyclosporine, oral contraceptives, oxycodone, and warfarin.^43,44 Patients need counseling about potential drug interactions with St. John’s Wort.

 

Limited clinical studies evaluating the impact of drug-dietary supplement interactions exist. Many interactions are theoretical, based on limited clinical evidence, animal research, and case reports.⁷ 

 

Table 5. Examples of Potential Drug-Dietary Supplement Interactions^7,17

 

Dietary Supplement	Medication	Interaction
Calcium	Quinolone and tetracycline antibiotics	Decreased antibiotic efficacy Take antibiotic 2 hours before or 4-6 hours after calcium
	Dolutegravir Elvitegravir	Reduced serum levels Take medication 2 hours before or 2 hours after calcium
Ginseng	Diabetes medications	Increase risk of hypoglycemia
	Immunosuppressants	Decreased effectiveness of immunosuppressant
Ginkgo	Anticoagulants	Increased risk of bleeding
Iron	Quinolone and tetracycline antibiotics	Decreased levels of antibiotics due to decreased absorption Take antibiotics 2 hours before or 4-6 hours after iron
Magnesium	Bisphosphonates	Decreased absorption
	Levodopa/carbidopa	Decreased bioavailability of levodopa/carbidopa
Niacin	Statins	Increased risk of myopathy or rhabdomyolysis
	Thyroid hormones	Antagonize the effects of thyroid hormone replacement
	Antihypertensive medications	Increased risk of hypotension due to niacin’s vasodilating effects
St. John’s Wort	Alprazolam	Decreased effects of alprazolam
	Oral Contraceptives	Decreased efficacy Counsel patients to use other forms of contraception
	Digoxin	Decreased levels of digoxin
	Omeprazole	Decreased effects of omeprazole
Valerian	CNS depressant drugs	Additive sedative effects
Vitamin B6	Phenytoin	Decrease levels and clinical effects of phenytoin
Vitamin D	Atorvastatin	Decreased absorption of atorvastatin
Vitamin E	Anticoagulants	Increased risk of bleeding
Zinc	Quinolone antibiotics	Decreased levels and effects of antibiotics Take antibiotic 2 hours prior or 4-6 hours after zinc

 

Pharmacy training emphasizes the importance of drug-drug interactions. It is important to remember that any substance introduced to the body, including food, beverages, and dietary supplements, has the potential to interact with medications.

Situation: It is another busy day in the pharmacy; prescriptions cover the bench, the phone rings constantly, and a pickup queue extends around the corner. A technician nervously approaches the pharmacist about a patient at the counter with a question regarding a supplement. The pharmacist throws down the spatula, muttering angrily about lacking the knowledge and training to answer the question properly. Sighing, he says, "I’ll just Google it."

 

Secret #7: Many websites provide clinically backed information on dietary supplements (and Google is not one of them!).

 

The vast amount of health information available via the Internet with just a few clicks of the keyboard is both a blessing and a curse. Google is now a verb, and a simple search returns millions of results in seconds. While this may seem like a blessing, the curse lies in the searcher's inability to recognize valid, accurate sources of information. In many searches, ads appear as search results adding to the confusion.

 

In addition to the Internet, consumers turn to social media for health information. Social media use increased from 27% in 2009 to 86% in 2019.⁴⁵ Information posted on social media provides communication about healthcare issues, potentially resulting in improved health care.⁴⁵ Unfortunately, inaccurate information abounds on the Internet and social media platforms, leading to consumer misinformation.^47-49

 

The FDA recently launched a new dietary supplement education initiative geared towards consumers, healthcare professionals, and teachers. The program, Supplement Your Knowledge, presents information about dietary supplements through a series of three videos. Educational materials, including fact sheets and infographics, are available in English and Spanish.⁵⁰

 

Many government agencies provide free access to information about dietary supplements and their side effects, toxicity, and drug interactions. There are also several paid subscription resources available. Table 6 lists many of the available information options.

 

Table 6. Sources of Information about Dietary Supplements

 

Resource	Website	Information
Dietary Supplement Education Program	https://www.fda.gov/food/healthcare-professionals/dietary-supplement-continuing-medical-education-program	Continuing medical education program Collaboration between FDA and AMA Series of 3 videos about dietary supplements Also contains links to educational materials and other websites with information about dietary supplements
Dietary Supplement Label Database	https://dsld.od.nih.gov	Current and historical label information on dietary supplement products marketed in the United States Useful to determine the contents of dietary supplement products
Food and Drug Administration	https://www.fda.gov/food/dietary-supplements/information-consumers-using-dietary-supplements	Information for consumers on using dietary supplements Links to educational resources and materials, consumer updates, alerts, recalls and other information
Google Scholar	https://scholar.google.com/	Source of information from many avenues including journals, books, and conference proceedings
Lexi-Comp Natural Products Database	Available via mobile app	Requires a paid subscription Alphabetical, searchable natural product database
Memorial Sloane Kettering Cancer Center	https://www.mskcc.org/cancer-care/diagnosis-treatment/symptom-management/integrative-medicine/herbs	Information on herbs, botanicals, and other products for both consumers and healthcare professionals Dietary supplement monographs IOS app: About Herbs Part of an online integrative medicine resource center
National Cancer Institute Office of Cancer Complementary and Alternative Medicine	https://cam.cancer.gov	Information for consumers and healthcare professionals about CAM as it relates to cancer therapy Information on current NCI CAM research
National Center for Complementary and Integrative Health	https://www.nccih.nih.gov	Information for both consumers and healthcare professionals about complementary health products and practices
National Library of Medicine - Medline Plus	https://medlineplus.gov/druginfo/herb_All.html	Online health information about drugs, herbs, and supplements for consumers Information sourced from the National Center for Complementary and Integrative Health and Natural Medicines Comprehensive Database
Natural Medicines Comprehensive Database	https://naturalmedicines.therapeuticresearch.com	Requires a paid subscription Professional monographs including information about effectiveness, safety, adverse effects, and interactions Information on specific commercial products Interaction checker Patient handouts in English, Spanish and French
Office of Dietary Supplements	https://ods.od.nih.gov	Information for both consumers and healthcare professionals General supplement information Information on supplements for specific purposes Fact sheets on dietary supplements and their ingredients
PubMed	https://pubmed.ncbi.nlm.nih.gov	Search engine for the National Library of Medicine Source of information from journals
United States Department of Agriculture	https://www.nutrition.gov/topics/dietary-supplements	Links to general information and resources on dietary supplements

 

 

Performing an Internet search via Google may seem like the quickest and easiest way to find the answer to an inquiry. Engaging with the patient, gaining additional information, and knowing where to look ultimately saves time. It is not necessary for one to be an expert in all dietary supplements, just to self-educate one supplement at a time.

 

Pause and Ponder: A patient shares the unfortunate news about a recent cancer diagnosis. He asks you about the use of herbs in the treatment of cancer. What advice would you give? 

Conclusion

You may have noticed a recurring theme throughout this activity. Education. Dietary supplement education is essential to patient safety given the current usage patterns and accessibility of the retail pharmacy team. Education needs to include the entire pharmacy team. Technicians are often the first point of contact at the pharmacy, commonly fielding patient questions. Knowing when to answer questions and when to involve the pharmacist is a necessary skill. Understanding the differences in oversight, the physiological effects of dietary supplement consumption, and the potential for drug interactions allows effective management and counseling of patients. It is important for healthcare providers to solicit information regarding patient consumption of dietary supplements.

 

 

Sidebar: Tips for Counseling Patients about Dietary Supplements

 

Carefully inspect the product to ensure intact product labeling

Ensure the safety seal is intact

Check for an expiration date or best used by date

Check for customer service or return information before ordering

Buy direct from a reputable company; many reputable companies sell through Amazon, avoid 3^rd party resellers

Check for the presence of a third-party certification seal

Before purchase, check the company’s website for information on quality standards

Pay attention to the appearance and smell of the product upon opening

Child-resistant packaging is not a requirement for dietary supplements; advise on proper storage of product

Reinforce the importance of including dietary supplements on a current medication list

 

 

 

 

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