Drug Guidelines May Endanger Kidneys

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New recommendations for vancomycin use in some patients found to increase nephrotoxicity risk.

 

CHICAGO—New guidelines recommending higher-than-traditional concentrations of vancomycin could result in nephrotoxicity, according to new data presented here at the recent Interscience Conference on Antimicrobial Agents and Chemotherapy. 

 

Vancomycin typically has been dosed to achieve a target trough range of 5-15 mg/L for most infections. Current guidelines, however, recommend attaining a trough concentration of 15-20 mg/L for meningitis, hospital-acquired pneumonia, and ventilator-associated pneumonia. Many hospitals nationwide have adopted these guidelines into their vancomycin-dosing protocols.

 

In addition, the use of vancomycin has been increased because of a growing problem with methicillin-resistant Staphylococcus aureus (MRSA) infections requiring hospitalization. Data on the potential risk of renal damage posed by higher vancomycin disease are limited.

 

Researchers at Western University of Health Sciences in Pomona, Calif., used the pharmacy database to screen for patients who had been administered vancomycin between January 2006 and December 2006. They conducted a retrospective chart review that looked at all patients age 18 and older who received vancomycin therapy for at least 72 hours and had at least one vancomycin level assessed.

 

The investigators defined nephrotoxicity as an increase of 0.5 mg/dL in serum creatinine or greater on two consecutive serum creatinine tests compared with baseline. The researchers excluded hemodialysis patients.

 

A total of 218 patients were included in the study, and they were divided into two groups: group 1 included 130 patients who had vancomycin levels of greater than 15 mg/L and group 2 had 88 patients who had drug levels of 5-15 mg/L. The incidence of vancomycin-associated nephrotoxicity in group 1 was nearly triple that of group 2 (18.2% vs. 6.2%).

 

“These findings are cause for us to stop and address what types of patients would most benefit from achieving these higher vancomycin troughs in light of the potential for nephrotoxicity incidence,” said lead investigator Megan Nguyen, PharmD, assistant professor of pharmacy practice at Western Univer-sity of Health Sciences, Pomona, CA.

 

Until now, most physicians have not considered vancomycin to have significant toxic effects on the kidneys when given alone. The new findings, however, are consistent with previous studies showing vancomycin at higher drug concentrations results in more nephrotoxicity. Vancomycin has been around for more than 50 years and, unfortunately, antibiotic research tends to focus on newer agents, Dr. Nguyen said. Nevertheless, she said it is imperative that there be continued research on vancomycin to assess the clinical benefits of achieving higher vancomycin levels in the treatment of MRSA infections and other illnesses.

 

“All physicians need to be aware of this issue and ask what the true clinical benefits are and whether they outweigh the risks when achieving these higher troughs,” Dr. Nguyen told Renal & Urology News. “We need to look at what may be occurring in different patient populations, especially patients with MRSA. We also found that duration of therapy played a role in predicting nephrotoxicity in some patients. The likelihood of developing nephrotoxicity was greater in patients who were also on concomitant nephrotoxic agents.”

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