November 26, 2014
Amoxicillin’s Drawbacks Might Outweigh Benefits for Questionable Prescriptions 

Robina, Australia—Amoxicillin and amoxicillin-clavulanic acid can cause diarrhea and candidiasis in patients taking the antibiotics, but at least one contributor to overuse is that the harms are underreported, according to a recent study.

The article, published recently in the CMAJ (Canadian Medical Association Journal), notes that amoxicillin is the most commonly prescribed antibiotic for respiratory infections by primary care physicians and often is prescribed in combination with clavulanic acid.

Especially considering the often minor benefit of antibiotics for respiratory infections, those should be weighed carefully against the harms, according to the study led by researchers at the Centre for Research in Evidence-Based Practice, Bond University, which is on the Gold Coast in Queensland, Australia.

“The root cause of antibiotic resistance is the overuse of antibiotics, and therefore these drugs should not be prescribed when the benefits do not outweigh the harms,” explained corresponding author Dr. Christopher Del Mar.

The study points out that evidence of common adverse effects is lacking because most data comes from observational studies rather than randomized controlled trials.

Conducting a systematic review of controlled trials involving adults and children, the researchers sought to qualify and quantify harms of amoxicillin to better inform physicians of the antibiotics’ risks and benefits.

The study relied on 25 studies with information about harms, suggesting under-reporting of adverse effects, according to the authors. The total number of participants was 10,519, with 4,280 receiving only amoxicillin, 1,005 receiving amoxicillin-clavulanic acid, and 5,234 receiving placebo.

Diarrhea was found to be more than three times as likely in people taking amoxicillin-clavulanate. Candidiasis was also associated with the use of amoxicillin-clavulanic acid as well as with amoxicillin.

The number of courses of antibiotics needed to harm was 10 for diarrhea with use of amoxicillin–clavulanic acid and 27 for candidiasis with amoxicillin (with or without clavulanic acid), according to the results.

“Reported harms were fewer than we expected from clinical anecdotal experience and observationally derived data, which have primarily reported common harms as rashes (at rates of 5%-8% of those treated and even higher, up to 20%, among those with mononucleosis treated with amoxicillin) and gastrointestinal disturbance,” the authors write.

“Under-reporting of harms in trials remains widespread, and until that problem is addressed, under-reporting will flow to systematic reviews and other evidence syntheses such as guidelines,” they added.

“The important consequence of under-reporting of harms is the tilting of the balance of benefits and harms towards amoxicillin,” Del Mar pointed out

The authors said they hope the results will be useful for healthcare professionals to discuss both the potential adverse effects—as well as general lack of efficacy—of common antibiotics to treat acute respiratory infections in primary care.

The ability “of clinicians and patients to make fully informed decisions about using amoxicillin and amoxicillin-clavulanic acid is hampered by poor measurement and reporting,” according to the report.

In a related commentary, Dr. Yoon Loke of the Norwich Medical School, University of East Anglia, Norwich, UK, writes that the “findings are important for prescribers and patients around the world who must weigh the benefits and harms of empiric amoxicillin therapy in situations clouded by diagnostic uncertainty.”

“Amoxicillin has been widely used for decades, and it seems shameful that data on harms are missing from so many trials,” Loke adds. “For this drug, clinicians and patients must not construe ‘absence of evidence of harm’ to be the same as ‘evidence of absence of harm.’”

U.S. Pharmacist Social Connect