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Ponazuril for Veterinary Use

by Barbara Forney, VMD

Basic Information

Ponazuril is a triazinetrione anti-protozoal drug. Other drugs within the triazine group include diclazuril and toltrazuril. Ponazuril is an active metabolite of toltrazuril; the alternate chemical name for ponazuril is toltrazuril sulfone. Ponazuril has broad spectrum activity against coccidia and protozoa. In 2011, the European Committee for Medicinal Products for Veterinary Use approved a combination product of toltrazuril and emodepside for use in the dog to treat mixed parasitic infections of roundworms and coccidia. This product is not available in the United States. In the United States, there is an FDA approved paste form of ponazuril (Marquis) that is used to treat Sarcocystis neurona in horses.

Dogs and Cats

Ponazuril may be used to treat Neospora, Toxoplasma and coccidiosis in dogs and cats. There is relatively little information in the literature regarding its clinical use other than case reports, but interest in the newer anti-coccidial drugs has increased due to the development of parasite resistance.

Ponazuril was found to be efficacious for the treatment of Cystoisospora ohioensis infections in two separate research studies using beagle puppies. No adverse effects due to treatment were noted in either study. In a study performed on mice, ponazuril was found to be efficacious both to prevent and to treat acute and chronic toxoplasmosis.

Ponazuril Side Effects

  • The most common side effects are mild gastro-intestinal upset including vomiting and diarrhea.
  • Keratoconjunctivitis sicca (KCS) has been reported in some dogs, particularly in breeds with a predisposition to KCS.


Safety during pregnancy or lactation has not been studied. In one study performed on stallions there was no effect on spermatogenesis.

Drug Interactions

No information regarding drug interactions was found.


Under research conditions, a 10x overdose of ponazuril repeated for 3 days caused no adverse effect on beagle puppies.

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Therapeutic Class

Dogs and cats

May Be Prescribed by Vets for:
Coccidia, Cystoisospora ohioensis, Toxoplasma andNeospora caninum

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About the Author

Dr. Barbara Forney

Barbara Forney, VMD

Dr. Barbara Forney is a veterinary practitioner in Chester County, Pennsylvania. She has a master's degree in animal science from the University of Delaware and graduated from the University of Pennsylvania School of Veterinary Medicine in 1982.

She began to develop her interest in client education and medical writing in 1997. Recent publications include portions of The Pill Book Guide to Medication for Your Dog and Cat, and most recently Understanding Equine Medications published by the Bloodhorse.

Dr. Forney is an FEI veterinarian and an active member of the AAEP, AVMA, and AMWA.