August 21, 2013
Broad Spectrum Varieties Are More Than 60% of Antibiotics Prescribed in Ambulatory Care

Salt Lake City, Utah—When U.S. physicians prescribe antibiotics, they opt for broad-spectrum types more than 60% of the time, even though many of the conditions they are treating are not even caused by bacterial infections, according to a new study from the University of Utah.

In more than a quarter of the cases studies, the infection stemmed from a virus, according to the report, published recently in the Journal of Antimicrobial Chemotherapy.

“It seems that the natural bias, when there is uncertainty about an infection's cause, is to err on the side of prescribing antibiotics,” said senior author Adam L. Hersh, MD, PhD, an infectious disease expert and assistant professor of pediatrics at the University of Utah. “Our study found that the majority of prescriptions are for antibiotics that kill a wider range of bacteria, and that they are most likely to be given when they're not needed, such as in cases of viral infections.”

Determining whether an infection is viral or bacterial can sometimes be difficult, which probably accounts for much of the overuse of antibiotics, he added.

Stronger antibiotics were most often used when patients presented with respiratory problems, skin infections, and urinary tract infections, according to the study.

“Broad-spectrum agents constitute the majority of antibiotics in ambulatory care,” the study concludes. “More than 25% of prescriptions are for conditions for which antibiotics are rarely indicated. Antibiotic stewardship interventions targeting respiratory and non-respiratory conditions are needed in ambulatory care.”

Study authors, who included a medical epidemiologist at the CDC, used a nationwide database with information on ambulatory care visits at physician offices and hospital-based outpatient and emergency departments. Reviewing data from between 2007 to 2009, they identified a sample of 238,624 visits by patients 18 and older at those medical facilities, finding that 61% of antibiotic prescriptions were for broad-spectrum drugs, such as fluoroquinolones. The remaining 39% of prescriptions were for narrow-spectrum antibiotics, such as amoxicillin and doxycycline.

Researchers estimate an average of 985 million annual ambulatory care visits for the 2007-to-2009 period, and antibiotics appeared to be prescribed in about 101 million of those visits each year—62 million in which broad-spectrum antibiotics were prescribed and 39 million in which narrow-spectrum antibiotic were prescribed, according to the report.

The study found that the most commonly prescribed antibiotics were quinolones (25% of antibiotics), macrolides (20%), and aminopenicillins (12%). Antibiotics were most commonly prescribed for respiratory conditions (41% of antibiotics), skin/mucosal conditions (18%), and urinary tract infections (9%).

Interestingly, broad-spectrum agents were more likely to be prescribed than narrow-spectrum antibiotics for respiratory infections for which antibiotics are rarely indicated—such as bronchitis—during visits to EDs and for patients older than 60 years old, according to the study.

Uncertainty about the cause of an infection is one factor in the overuse of broad-spectrum antibiotics, according to Hersh, who also cited the misperception by physicians that their patients expect an antibiotic when they make an office visit. That is changing, he suggested, because of efforts to educate patients about the problems associated with overuse of antibiotics, such as CDC’s “Get Smart: Know When Antibiotics Work” program.

“The public is increasingly aware of the downside and side effects of antibiotics,” he noted. “Actually, when they see their doctor, most patients just want an explanation as to what's wrong and are open to considering why an antibiotic wouldn’t be helpful.”

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