The manufacturer, Norbrook Laboratories of Lenexa, Kan., received FDA approval March 29 of an Abbreviated New Animal Drug Application for Enroflox 100 (enrofloxacin), a generic version of Bayer HealthCare’s Baytril 100.

Bayer won a temporary restraining order April 12 that suspended the FDA’s approval of Enroflox and the label. Bayer, based in Shawnee Mission, Kan., contended that labeling the administration of Enroflox as a multiple-dose regimen would be ignored by practicing veterinarians, who instead would deliver a single high dose, harming sales of Baytril 100, which has single-dose approval.

Three cattle veterinarians retained by Bayer concluded that the generic drug, labeled for multiday administration, "would be used in a single high dose, notwithstanding the instructions on the label.”

"The uncontroverted record evidence is that the generic product is reasonably certain to be used off-label in a single high dose,” Bayer asserted in court documents.

The U.S. District Court in Washington, D.C., issued the temporary restraining order and scheduled an April 25 hearing on Bayer’s motion for a preliminary injunction.

A Norbrook spokeswoman declined to comment.

Bayer began marketing Baytril 100, a fluoroquinolone antibiotic, in 1998 as a single high-dose treatment, which the company described as a revolutionary development.

"For many years the conventional wisdom was that [bovine respiratory disease] had to be treated by administering multiple low doses of antibiotic—a time-consuming, expensive and cumbersome practice,” the company noted.

Norbrook submitted its Abbreviated New Animal Drug Application for generic Baytril 100 in 2008, beginning a five-year process that ended with the FDA’s approval last month.

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