Study Finds Efforts to Curb Antibiotic Usage in Ambulatory Settings are Successful

Researchers with Vanderbilt University Medical Center’s Department of Preventive Medicine have completed a large epidemiologic study to assess United States usage trends for antibiotic prescriptions. The study, which examined antibiotic prescription data from 1995 through 2006 to assess whether initiatives that began in the mid-1990s to curb antibiotic use have had a positive impact on prescribing, found the efforts to curb unnecessary prescriptions effective.

The study, published in the Aug. 19 issue of the Journal of the American Medical Association (JAMA), found that during this period there was an overall 36 percent reduction in U.S. antibiotic prescriptions for acute respiratory tract infections (ARTI) in children younger than 5, the age group that typically has the highest rates of antibiotic utilization. By the end of 2006, the Healthy People 2010 target of 56 antibiotic courses prescribed for ear infections per 100 children younger than 5 was already reached. Healthy People 2010 is a broad based U.S. Health and Human Services (HHS) initiative.

“Our study suggested two main reasons for this decline -- a decrease in prescribing of antibiotics inappropriately used for viral infections, and a decrease in doctor visits for ear infections,” said Carlos Grijalva, MD, MPH, assistant professor of preventive medicine at Vanderbilt, and the study’s lead author. “Ear infections remain the leading cause of antibiotic prescribing in U.S. children. Although the proportion of children who receive antibiotics for ear infections is about 80 percent, and remained unchanged over the 12-year study, the decline in visits for ear infections was a major cause for the reduction in overall antibiotic use in children,” he said.

The study analyzed annual data from the National Ambulatory Medical Care Survey (NAMCS) and the National Hospital Ambulatory Medical Care Survey (NHAMCS) between 1995 and 2006. NAMCS gathers data on a nationally representative sample of visits to office-based physicians involved in direct patient care, while NHAMCS collects data on a representative sample of visits to hospital-based emergency departments and outpatient clinics. There were 6.2 billion ambulatory visits in the United States during this period, the surveys estimated. Overall, antibiotics were prescribed in 13 percent of all ambulatory visits. Acute respiratory tract infections accounted for 10 percent of all visits and for 44 percent of antibiotic prescriptions.

From 1980 through 1992, antibiotic prescription rates in the United States had increased by 48 percent. Most of these prescriptions were for acute respiratory tract infections, with the highest use in children younger than 5. During this same period health care professionals witnessed a rapid emergence of disease caused by antibiotic-resistant bacteria.

Antibiotic-resistant infections are difficult to treat, often require longer and more expensive treatment options, and can in some instances become life-threatening.

In the 1990s, the Centers for Disease Control and Prevention (CDC), several local and state health departments (including Tennessee) and academic institutions launched a national campaign to reduce inappropriate use of antibiotics. In addition to these efforts, a new vaccine, the pneumococcal conjugate vaccine, was introduced in 2000. The pneumococcal conjugate vaccine is recommended for all infants in the United States. This vaccine prevents several bacterial infections in children, including pneumococcal bacteremia, meningitis, pneumonia and ear infections.

Grijalva and co-authors Marie Griffin, MD, MPH, professor of preventive medicine , and J. Pekka Nuorti, MD, DSc, medical epidemiologist at the CDC, found that while overall antibiotic prescription rates for respiratory tract infections decreased during the study period, the number of prescriptions for selected broad-spectrum antibiotics began to surge, including prescriptions for azithromycin (a macrolide) increasing ninefold among children younger than 5.

“Some of the broad-spectrum antibiotics can be given once or twice a day, rather than three or four times. Similarly, some broad spectrum antibiotics have a shorter duration of treatment, thus, the ease of administration is a factor for this preference. Also, these antibiotics have been heavily promoted so people think they are more effective, but sometimes they are not,” Grijalva said. “Some are recommended as first choice for serious infections, such as pneumonia, but they are sometimes used for conditions for which they are not first choice. These increases are of concern because infections caused by antibiotic-resistant bacteria increased dramatically during recent years.”

The study found that among children younger than 5, approximately 23 percent of doctor visits due to acute respiratory infections for which antibiotics are rarely indicated were still receiving antibiotic prescriptions in 2006. This proportion was 48 percent for persons 5 and older.

“Antibiotics are an important tool for treating serious infections. We are at risk of losing that tool if antibiotics are misused. Despite the increases in antibiotic-resistant bacteria, the development of new antibiotics is scarce,” Grijalva said. “Vaccinations that reduce respiratory infections will reduce antibiotic use, both appropriate and inappropriate. Antibiotics should be reserved for bacterial infections, and broad spectrum antibiotics should be reserved for the most serious of these."