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Animal & Veterinary

FDA Alerts Horse Owners and Veterinarians About Adverse Events Associated with Certain Unapproved Compounded Drugs in Horses

Two lots of pyrimethamine/toltrazuril drugs compounded by Wickliffe Pharmacy associated with illnesses and deaths

May 15, 2014

Media Inquiries: Siobhan DeLancey, 202-510-4177,
Consumer and Industry Inquiries:

The U.S. Food and Drug Administration is alerting horse owners and veterinarians that two lots of compounded combination drug products containing pyrimethamine and toltrazuril, used to treat the neurologic disease Equine Protozoal Myeloencephalitis (EPM), have been associated with adverse events in ten horses.

The products were compounded by Wickliffe Pharmacy of Lexington, Ky. One lot was compounded as a paste and one as an oral suspension. All of the products in these lots are accounted for and are no longer in distribution.

FDA is working with the pharmacy and state partners to investigate these adverse events.

At this time, FDA testing indicates that one lot of product contained higher levels of pyrimethamine than the labeling indicates. Adverse events associated with high doses of pyrimethamine include seizures, fever and death.

FDA has received reports of adverse events--including seizures, fever and death--involving two horses in Kentucky and eight horses in Florida that were administered these products. Four horses have died or been euthanized and six horses are recovering.

Horse owners, caretakers and veterinarians should report to FDA any symptoms such as seizure, fever or collapse in horses who might have received high doses of pyrimethamine. During the course of this on-going investigation into the adverse reactions, it has come to the attention of FDA that elevated doses of pyrimethamine may have been used by some practitioners with negative results. The usual dose of pyrimethamine in horses is 1 mg/kg, which has been shown to be safe for the treatment of EPM in an FDA-approved combination product containing pyrimethamine and sulfadiazine.

These compounded combination products are not approved animal drugs. Additionally, toltrazuril is not approved for use in horses. In general, FDA has serious concerns about unapproved animal drugs, including certain compounded animal drugs. These drugs are not evaluated by FDA and may not meet FDA’s strict standards for safety and effectiveness. Unapproved animal drugs also may not be labeled or advertised appropriately. Horse owners or caretakers should consult with their veterinarians about other therapies.

Drugs that have been evaluated and approved by FDA for the treatment of EPM include ponazuril, diclazuril, and a combination drug of pyrimethamine and sulfadiazine.

Owners and veterinarians can report complaints about FDA-regulated animal drug products by calling the consumer complaint coordinator in their area or by filing a Veterinary Adverse Drug Reaction report. Information on reporting consumer complaints can be found at:

Contact FDA

240-276-9115 FAX
Issued by: FDA, Center for Veterinary Medicine

7519 Standish Place, HFV-1

Rockville, MD 20855

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