The results of a new study indicate that at least one out of every four antibiotics prescribed during ambulatory care visits were inappropriate.

The study, published in BMJ, examined data from the 2015 National Ambulatory Medical Care Survey. Researchers analyzed more than 28,000 sample visits representing close to a billion ambulatory care visits nationwide.

Their conclusions include the following:

• Antibiotics were prescribed during about 13% of ambulatory care visits in 2015.

• About 25% were for inappropriate indications (~32 million prescriptions).

• In addition, 18% lacked a documented indication (~24 million prescriptions).

• Combined, as many as 43% of prescriptions were potentially inappropriate.

• Factors contributing significantly to antibiotic prescribing without an indication were being an adult male, having at least one chronic disease, spending more time with the provider and seeing a non-primary care specialist.

• Prescriptions for sulfonamides and urinary anti-infectives were commonly associated with the absence of a documented infection.

In the study's conclusion, researchers state, "Antibiotic prescribing in the absence of a documented indication may severely bias national estimates of appropriate antibiotic use in this setting and misinform antimicrobial stewardship efforts. … With 60% of antibiotic expenditure and up to 90% of antibiotic use originating in ambulatory care settings, more focus is needed to support well informed stewardship efforts beyond the hospital."