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.