Atlanta—About half of antibiotic prescriptions pharmacists filled for patients with respiratory ailments were likely inappropriate, according to a new public health study finding that, overall, an estimated 30% of outpatient oral antibiotic prescriptions in the United States were unnecessary in a recent 1-year time period.

The article, which was published in the Journal of the American Medical Association, reports the high rate of inappropriate outpatient antibiotic prescribing in 2010-2011 and argues for better stewardship of the drugs to combat antibiotic resistance.

Researchers from the CDC led the study, which sought to determine the percentage of antibiotic use that is inappropriate and amenable to reduction among the more than 260 million prescriptions dispensed.

To determine that, CDC researchers used the 2010-2011 National Ambulatory Medical Care Survey and National Hospital Ambulatory Medical Care Survey to estimate the rates of outpatient oral antibiotic prescribing by age and diagnosis, as well as which ones might have been inappropriate in adults and children.

Results indicate that, of the 184,032 sampled visits, 12.6% resulted in antibiotic prescriptions. Patients with sinusitis received antibiotic prescriptions 56 out of a 1,000 times, followed by suppurative otitis media with 47 and pharyngitis with 43.

Researchers used a tiered system to determine appropriate antibiotic prescribing. Sinusitis, suppurative otitis media, and pharyngitis fall into the second tier for which an antibiotic might be indicated in some cases.

In total, acute respiratory conditions led to 221 antibiotic prescriptions per 1,000 population annually, but researchers estimate that just 111 of those were appropriate for the conditions. Among all conditions and ages during the study period, 353 antibiotic prescriptions per 1,000 population out of the 506 dispensed were adjudged to be appropriate.

“Half of antibiotic prescriptions for acute respiratory conditions may have been unnecessary, representing 34 million antibiotic prescriptions annually,” the CDC researchers write. “Collectively, across all conditions, an estimated 30% of outpatient, oral antibiotic prescriptions may have been inappropriate. Therefore, a 15% reduction in overall antibiotic use would be necessary to meet the White House National Action Plan for Combating Antibiotic-Resistant Bacteria goal of reducing inappropriate antibiotic use in the outpatient setting by 50% by 2020.”

The annual antibiotic prescription rate was highest for children aged 2 years and younger, at 1,287 per 1000 population, according to the report. Regionally, use of the anti-infectives was highest in the South, with 553 prescriptions per 1,000, compared to the West, with the lowest rate at 423.

In an accompanying commentary, Pranita D. Tamma, MD, MHS, and Sara E. Cosgrove, MD, MS, of the Johns Hopkins University School of Medicine in Baltimore called the estimates “conservative,” but suggest the results “offer an important and useful starting point to understand prescribing practices in the ambulatory care setting. Such estimates are necessary to guide public health and outpatient stewardship efforts.

“Attempts to improve outpatient antibiotic prescribing likely require two complementary strategies: (1) changing clinician behavior to alleviate concerns related to diagnostic uncertainty, alienating patients, and not conforming to peer practices and (2) educating patients and families about the role of antibiotics in medical care,” Tamma and Cosgrove add.

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