The increase was mainly driven by rising use of broad-spectrum agents and vancomycin (Vancocin), Ronald Polk, Pharm.D., of Virginia Commonwealth University, and colleagues reported in the Nov. 10 issue of Archives of Internal Medicine.
The study is, they said, "the largest and most current of such reports" and was made possible by electronic claims data collected by 22 members of the University Health System Consortium.
The researchers noted that few multicenter investigations have looked at antibacterial use, although the CDC has examined what happens in intensive care units.
To fill the gap, they analyzed data from the University Health System Consortium, an organization of academic health centers from January 1, 2002 through December 31, 2006. In 2002, 23 members allowed access to claims data, a number that increased to 35 in 2006.
Among those 35 hospitals in 2006, the researchers found, 775,731 adult patients were discharged and 492,721 -- or 63.5% -- got at least one dose of an antibacterial drug.
However, there was marked variation among hospitals, the 2006 snapshot showed, with average use ranging from 589 to 1,235 days of therapy per 1,000 patient-days.
Among the 22 hospitals that had five years of claims data, the researchers found, total antibacterial use increased each year, from an average of 798 days of therapy per 1,000 patient-days in 2002 to 855 in 2006. The trend was significant at P=0.02.
Among all agents, the total use of five broad-spectrum antimicrobial classes increased significantly, from an average of 361 days of therapy per 1,000 patient-days in 2002 to 386 in 2006 (P=0.01).
But there were major differences among the groups, Dr. Polk and colleagues found:
- The use of ÃŸ-lactam and ÃŸ-lactamase inhibitor drugs rose significantly (P<0.05), owing to increased use of a single agent, piperacillin-tazobactam (Zosyn). Average use of piperacillin-tazobactam increased by 84%, from 38 days of therapy per 1,000 patient-days in 2002 to 75 in 2005 and 70 in 2006. The trend was significant at P<0.001.
- Use of carbapenems increased by 59% during the five years, from a mean of 22 days of therapy per 1,000 patient-days in 2002 to 35 in 2006. The increase was significant at P<0.001.
- On the other hand, use of the aminoglycoside medications, such as gentamicin, decreased by 29%, a trend that was also significant at P<0.001.
- There was a slight but non-significant increase in use of third- and fourth-generation cephalosporins.
- Total fluoroquinolone use fell slightly but the decrease was not significant. The fluoroquinolones remained the most commonly prescribed class of antibacterials.
The increased use of carbapenems and piperacillin-tazobactam occurred despite sporadic shortages, the researchers said, "suggesting that the rate of increase may accelerate as the shortage is alleviated."
The other factor contributing to the overall increase was a rise in the use of vancomycin, the researchers said, for reasons that are "likely multifactorial."
The average use of the medication increased 43% during the study period, from 87 days of therapy per 1,000 patient-days on average in 2002 to 124 in 2006, a trend that was significant at P<0.001.
The investigators noted several limitations to the study, including the fact that "administrative claims databases are rarely validated."
They also noted that they were unable to determine whether antibacterial use was appropriate and they did not attempt to quantify the use of daptomycin and tigecycline, which became available during the study period.
|The study was funded in part by an investigator-initiated grant from Bayer (later assumed by Schering-Plough).
- Reviewed by Dori F. Zaleznik, MD Associate Clinical Professor of Medicine, Harvard Medical School, Boston
Archives of Internal MedicineSource Reference: Pakyz AL et al "Trends in Antibacterial Use in US Academic Health Centers: 2002 to 2006" Arch Intern Med 2008; 168(20): 2254-2260.