Portland, OR—What percentage of antibiotic prescriptions from outpatient office visits were written without a documented reason for doing so? Pharmacists, who fill them, might be surprised by the answer.

A study in The BMJ determines that, during a 1-year period, 18% of antibiotic prescriptions fell into that category. Oregon State University College of Pharmacy–led researchers point out that unnecessary prescribing of antibiotics not only needlessly exposes patients to side effects but also contributes to the growing global threat of antibiotic resistance.

“Antibiotic prescribing without making note of the indication in a patient’s medical records might be leading to a significant underestimation of the scope of unnecessary prescribing,” said lead author Michael J. Ray MPH. “When there’s no indication documented, it’s reasonable to think that at least some of the time, the prescription was written without an appropriate indication present.”

Researchers sought to identify the frequency, in the ambulatory-care setting, of antibiotics being prescribed without a documented indication. The reason was to quantify the potential effect on assessments of appropriateness of antibiotics, and to understand patient-, provider-, and visit-level characteristics associated with antibiotic prescribing without a documented indication.

Used for the cross-sectional study was the 2015 National Ambulatory Medical Care Survey. The authors focused on 28,332 sample visits representing 990.9 million ambulatory care visits nationwide. They documented whether each antibiotic prescription was accompanied by appropriate, inappropriate, or no documented indication as identified through ICD-9-CM (international classification of diseases, 9th revision, clinical modification) codes.

The study determined that antibiotics were prescribed during 13.2% (95% CI, 11.6%-13.7%) of the estimated 990.8 million ambulatory care visits in 2015. Based on the criteria, 57% (52% to 62%) of the 130.5 million prescriptions were for appropriate indications, 25% (21% to 29%) were inappropriate, and 18% (15% to 22%) had no documented indication, the researchers point out.

“This corresponds to an estimated 24 million prescriptions without a documented indication,” the authors wrote. “Being an adult male, spending more time with the provider, and seeing a non-primary care specialist were significantly positively associated with antibiotic prescribing without an indication. Sulfonamides and urinary anti-infective agents were the antibiotic classes most likely to be prescribed without documentation.”

“Sixty percent of antibiotic expenditures originate in ambulatory care settings,” Ray noted. “And up to 90% of antibiotic use originates there. Clearly more focus is needed to support well-informed stewardship efforts.”

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