Many antibiotics overprescribed for outpatients

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Prescriptions for antibiotics written by non-physician providers — nurse practitioners and physician assistants — increased over a six-year period, and many drugs were prescribed inappropriately, according to a new study by researchers at the College of Pharmacy.

Antibiotic resistance, combined with slowed development of new antimicrobials, have created a public health crisis, causing at least two million illnesses and 23,000 deaths and costing more than $10 billion each year, according to the U.S. Centers for Disease Control and Prevention.

Stewardship programs that promote the proper use of antimicrobials — including antibiotics — aimed at improving patient outcomes, reducing drug resistance, and decreasing the spread of multi-drug resistant infections are being developed, but most are focused on inpatient settings.

But the majority of antibiotics are overprescribed in outpatient sites, said Katie Suda, research associate professor of pharmacy systems, outcomes and policy and lead author of the study, published in the Journal of the American Pharmacists Association.

“It’s estimated that 30 percent of all antibiotics in outpatient clinics are unnecessary,” Suda said. “Understanding prescribing trends over time by provider groups can be helpful in customizing programs promoting the appropriate use of antimicrobials.”

Antibiotics are ineffective against viruses, and the best treatment for viral illnesses are antivirals and/or symptomatic remedies such as over-the-counter cough and cold products, Suda said.

“Use of an antibiotic for a viral illness does not make the patient feel better any faster or decrease the spread of the viral illness to someone else,” she said. “However, there is a risk of antibiotic-related adverse events, such as bacterial resistance, a superinfection such as Clostridium difficile infection, or other side effects.”

Suda reviewed data from 2005 through 2010 for six classes of antibiotics — cephalosporin, macrolides, penicillin, quinolone, sulfonamides and tetracyclines. During that time, 1.56 billion antibiotic prescriptions were dispensed, and the majority of the patients were seen in community settings — outpatient clinics, doctors’ offices, retail clinics or emergency departments.

Physicians wrote the highest percentage (81 percent) of prescribed antibiotics, with dentists second, at just over 10 percent. But scripts written by those two groups decreased over the time of the study. The number of prescriptions written by nurse practitioners and physician assistants during that time more than doubled.

“This may be a reflection of the increasing autonomy and, thus, number of infections treated by these providers,” Suda said. “Retail clinics affiliated with a pharmacy and/or retail chain emerged during the study period and may also have contributed to these results.”

Penicillin and related drugs were the most-prescribed antibiotics by all groups. Macrolides were the second most common class prescribed by physicians, physician assistants and nurse practitioners, followed by cephalosporins, quinolones, sulfonamides and tetracyclines.

Use of antibiotics, especially broad spectrum agents that cover a wide range of bacteria, leads to resistance and is a patient safety concern, Suda said. However, prescribing of broad spectrum antibiotics are increasing nationally, she said.

“We found that broad spectrum antibiotics significantly increased only for nurse practitioners and physician assistants, and that these groups are likely responsible for the increases,” she said.

Suda also discovered that the number of prescriptions written by physicians, nurse practitioners and physician assistants significantly increased in the winter months compared to summer, with the highest increase being from nurse practitioners. Dentists did not exhibit any seasonal trends in prescribing.

“Seasonality of antibiotic prescribing can be an indicator of inappropriate use and is primarily driven by the macrolide and penicillin classes,” Suda said. Increases in antibiotic prescriptions by physicians, nurse practitioners and physician assistants in the winter months could be due to diagnosing viral illnesses in outpatient settings, she said.

“These trends are likely due to the increase in respiratory tract infections, most of which are viral in nature, and which commonly occur in the first and fourth quarters of the calendar year,” Suda said.

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