Needle hasn't moved on US outpatient antibiotic prescribing

Despite an increasing focus on reducing unnecessary antibiotic use in recent years, national outpatient prescribing practices remain unchanged, according to a study today in Infection Control and Hospital Epidemiology.

Analyzing administrative claims data for the years 2013 through 2105, researchers from the Washington University School of Medicine in St. Louis and Boston University School of Medicine found no significant changes in overall annual antibiotic prescribing rates or prescribing rates for individual drugs over the 3-year period. But they did find significant seasonal variation, with antibiotics much more likely to be prescribed in the winter than in the summer.

Although the study did not assess whether antibiotics were prescribed appropriately, the authors of the study say the findings are somewhat surprising, given the focus that public health organizations and medical professional organizations have placed on outpatient prescribing in recent years. The lack of any change in prescribing rates, they conclude, suggests that guideline-based best practices and educational materials are not enough to change prescribing practices.

"From a public health standpoint, we probably need to do more to engage primary care providers, patients, and public health agencies to address the issue of outpatient antibiotic prescribing," lead author Michael Durkin, MD, MPH, an assistant professor of medicine at Washington University School of Medicine, told CIDRAP News.

No reduction in prescribing rates

The analysis of data from pharmacy benefits manager Express Scripts showed that 98 million antibiotic prescriptions were filled from 2013 through 2015 from a sample of nearly 39 million insured members. The mean number of prescriptions per 1,000 beneficiaries was 826, with the rate falling from 829 in 2013 to 799 in 2014, then jumping up to 851 prescriptions per 1,000 beneficiaries in 2015.

The five most commonly prescribed antibiotics were azithromycin, amoxicillin, amoxicillin/clavulanate, ciprofloxacin, and cephalexin. There were no statistically significant changes in prescribing rates over the study period for any of these drugs.

Analysis of seasonal prescribing trends showed that overall and individual antibiotic prescribing varied by month, with overall prescribing 42% higher in February, the peak month, than in September. This trend was observed in the top three antibiotics (azithromycin, amoxicillin, and amoxicillin/clavulanate), with usage of azithromycin in February being 146% higher than in August. But the trend was reversed for ciprofloxacin and cephalexin, which were prescribed more during the summer months.

Durkin and his colleagues explain that the seasonal variation in prescribing could suggest inappropriate use, with more patients in winter being treated for respiratory conditions, which are frequently caused by viruses and don't require antibiotics. But they note that bacterial conditions like pneumonia are also more prevalent during winter, so some of the increased prescribing may well have been appropriate. Because the analysis didn't include any microbiology or medical claims data, the authors couldn't determine whether these prescriptions were inappropriate or not.

"Some of the seasonal variations could be appropriate," Durkin said.

But a certain amount of inappropriate prescribing is assumed. The Centers for Disease Control and Prevention (CDC) estimates that roughly 30% of outpatient antibiotics are unnecessary, and Durkin said he believes that estimate is on the conservative side.

The finding that the use of ciprofloxacin and cephalexin is higher in the summer months was a new finding that hasn't previously been described. But the authors say this also isn't surprising, since these antibiotics are used to treat urinary tract infections and skin- and other soft-tissue infections, which are more common during the summer months.

Guidelines alone not sufficient

The results don't reflect a lack of attention to the issue.

The CDC's Get Smart campaign to reduce antibiotic use in outpatient settings was initially launched in 2003, and the agency has been a vocal advocate for antibiotic stewardship in all medical settings. The American Board of Internal Medicine Foundation, through its Choosing Wisely campaign, has been working with several medical societies on recommendations and guidelines for antibiotic prescribing since 2013. Durkin said he and his co-authors thought that these efforts might have produced more of an impact.

"We were hoping that some of the messaging and some of the information that's been disseminated from the CDC and other key stakeholders would have had more of an impact on community outpatient antibiotic prescribing," Durkin said.

But Durkin added that it can be difficult for providers to keep up with new guidelines, which are being released with increasing frequency. In addition, other studies have shown that guidelines may not be the most effective means of changing prescribing behavior. "Relying on guidelines from professional societies alone is probably not sufficient," Durkin said. "You need a multifaceted approach."

Durkin and his colleagues suggest that interventions such as antibiotic prescription benchmarking, audit and feedback, and education sessions could all be incorporated into outpatient antibiotic stewardship programs to reduce unnecessary prescribing. Durkin also stressed that guidelines and educational materials remain important tools for reinforcing appropriate prescribing behavior.

"One of the big issues that we need to figure out is the most effective way to share those with frontline providers," he said.

See also:

Mar 8 Infect Control Hosp Epidemiol study

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