Study shows more risk with Pfizer antibiotic: FDA

WASHINGTON (Reuters) - The U.S. Food and Drug Administration on Friday issued a safety alert over Pfizer Inc.'s antibiotic Zyvox after a clinical trial found a higher chance of death in seriously ill patients given the drug.

The study, which compared Zyvox to three other antibiotics, looked at patients with bloodstream infections related to catheters, the FDA said.

Zyvox, also known as linezolid, is approved in the United States to treat a variety of bacterial infections, including pneumonia and skin infections as well as those resistant to other drugs.

Representatives for Pfizer on Friday had no immediate comment.

In the trial, Zyvox was compared to three rival drugs vancomycin, oxacillin and dicloxacillin.

"Patients treated with linezolid had a higher chance of death than did patients treated with any comparator antibiotic, and the chance of death was related to the type of organism causing the infection," the FDA said on its Web site here .

Depending on their type of outer membrane, bacteria can be considered either gram-negative or gram-positive.

Zyvox patients infected with gram-negative bacteria, both gram-positive and gram-negative bacteria, or who were infection-free when they entered the study saw a greater risk of death. Those with only gram-positive bacteria infections did not.