Antibiotic prescription patterns violate guidelines, increase costs

January 13, 2002

Despite guidelines that have been in place for nearly a decade, only 24 percent of the antibiotics prescribed for women's urinary tract infections are the recommended drug, down from 48 percent 10 years earlier. Physicians write 2.45 million such prescriptions each year. The alternative medications are no more effective, encourage the spread of antibiotic resistance, and cost 11 to 40 times as much.

The findings are published in the January 14 issue of the Archives of Internal Medicine.

"We found that from 1989 to 1998 physicians were increasingly likely to manage these common infections in ways that encourage antibiotic resistance and waste money," said Elbert S. Huang, MD, MPH, an instructor of medicine at the University of Chicago and author of the study. "This trend appears to result from non-clinical forces such as pharmaceutical promotions and sub-specialty culture."

Guidelines for the treatment of urinary tract infections (UTI) have not changed significantly since the early 1990s. For example, a well-known 1993 review article and 1999 guidelines from the Infectious Disease Society of America both recommend trimethoprim-sulphamethoxazole (best known as Bactrim) as standard therapy, with certain fluoroquinilones as second-line choices.

Trimethoprim-sulphamethoxazole costs only $1.79 for a ten-day supply. Nitrofurantoin (Macrodantin), prescribed in 30 percent of cases, costs $20.34 for 10 days. Fluoroquinolones, used in 29 percent of cases, can cost as much as $70.98, as in the case of ciprofloxaxin (Cipro).

Huang and colleague Randall Stafford, MD, PhD, of Stanford University, analyzed a representative sample of 1,478 outpatient visits for uncomplicated urinary tract infections over the 1990s. They found that fewer and fewer physicians, and never more than half, followed the guidelines.

In 1989-90, 48 percent of UTI antibiotic prescriptions were for trimethoprim. That fell to 24 percent by 1997-1998. Fluoroquinilone use increased from 19 percent to 29 percent by 1998. Nitrofurantoin use rose from 14 percent to 30 percent.

Different specialties preferred different drugs. General practitioners were the most likely to prescribe trimethoprim. Internal medicine specialists more often offered fluoroquinilones and rarely prescribed nitrofurantoin. Obstetrician/gynecologists were most likely to prescribe nitrofurantoin, which is thought to be less likely to contribute to birth defects, but is not recommended in the specialty literature as a first-line treatment for urinary tract infections during pregnancy.

"The literature and the guidelines are consistent, but physician behavior is quite variable," noted Huang.

Although the study wasn't designed to explain why the variations occurred, the authors suggest that targeted promotional efforts by drug makers played a major role in moving the specialists away from cheaper to more costly drugs, "without a concurrent increase in effectiveness."

A simple calculation reveals how much is at stake. If all 2.45 million antibiotic prescriptions were for a three-day course of trimethoprim, medication costs would be only $1.3 million. If all those prescriptions were changed to ciprofloxacin the costs would increase to $52.2 million.

This is a small but revealing segment of a huge expenditure, said Huang.

In 2000, spending on drugs increased by 17.3 percent, a slightly smaller increase than the 19.2 percent jump seen in 1999 but still the fastest growing category of health spending, according to a recent report from the Department of Health and Human Services. Spending on prescription drugs topped $120 billion in 2000, three times the amount spent in 1990.

"Antibiotic prescribing should be shaped to decrease antimicrobial resistance and costs," note the authors. "We observed prescribing patterns that ran counter to those goals."

An award to Huang from the Public Health National Research Service and a grant to Stafford from the National Heart, Lung and Blood Institute supported this study.