The U.S. Food and Drug Administration (FDA) is asking a federal court to stop Franck's Compounding Lab Inc. from manufacturing and selling compounded drugs used to treat animals. The Ocala, Fla., pharmacy produced a vitamin and mineral compound blamed for the deaths of 21 polo horses last year.

The horses died after receiving a selenium, vitamin B, and potassium compound prepared by the pharmacy. A subsequent investigation into the deaths revealed the compound contained levels of selenium toxic to horses.

In a complaint filed April 16 in the U.S. District Court for the Middle District of Florida, the FDA alleges that the pharmacy compounds animal drugs from bulk ingredients without the agency's approval and that the drugs endanger animal health.

The pharmacy responded to the complaint in a prepared statement