The Food and Drug Administration slapped Pfizer with a warning letter over a four-page journal ad for its Zyvox antibiotic.

The agency’s Division of Drug Marketing, Advertising and Communications (DDMAC) said the ad failed to meet the fair balance requirement by omitting risk information, expanded the indication of the drug and made unsubstantiated claims of superiority to vancomycin for the treatment of pneumonia based on insufficient studies.

The letter, dated July 20, reads in part, “Your misleading promotion of Zyvox, and in particular, your unsubstantiated implied claims regarding its superiority to vancomycin, poses serious public health and safety concerns because of its potential to result in the inappropriate use of Zyvox, which is associated with increased toxicity relative to vancomycin.”

Zyvox professional advertising is handled by Cline, Davis & Mann.