SAN FRANCISCO – Linezolid works better than vancomycin in obese patients with MRSA pneumonia, according to an industry-supported analysis.
Clinical success – ICU or hospital discharge by day 14 in the absence of death, therapy change, or intubation – was more likely among 49 patients with body-mass-indices of 30 or more treated with 600 mg of linezolid IV or orally every 12 hours, the standard dose, than among 740 treated with standard dosing of vancomycin (HR 1.77, 95% CI 1.18-2.64). The findings come from a national retrospective cohort analysis of Veterans Affairs hospital data. The study was funded in part by Pfizer, which markets linezolid as Zyvox.
"Clinical success rates were higher [in obese patients] with linezolid. We don’t know exactly why," lead investigator Aisling Caffrey, Ph.D., assistant professor of pharmacoepidemiology at the University of Rhode Island College of Pharmacy in Kingston, R.I., said at the Interscience Conference on Antimicrobial Agents and Chemotherapy.
Maybe it was because vancomycin dosing is, in part, weight based and perhaps problematic for obese patients. Clinicians may be reluctant to exceed standard dosing even if BMIs suggest it, due to toxicity concerns; it’s unclear if patients in the study received adequate doses.
Linezolid "is a little more straightforward. Maybe obese patients were more likely to get the right dose," Dr. Caffrey said.
She and her coinvestigators hope to look further into the antibiotic treatment of MRSA pneumonia in the overweight population.
The investigation was a subgroup analysis of a larger MRSA pneumonia comparison study that found nonobese patients treated with linezolid were less likely to have 30-day hospital readmissions (HR 0.60, 95% CI 0.37-0.97). There were no other outcome differences between the drugs. Patients in the study were treated for at least 3 days.
The conference was sponsored by the American Society for Microbiology. Pfizer and the Department of Veterans Affairs funded the study. Two of the researchers were Pfizer employees. Dr. Caffrey\'s research is funded in part by Pfizer.