Ponazuril (brand names: Toltrazuril sulfone®, Marquis®, Ponalrestat®) is an antiprotozoal medication used to treat equine protozoal myeloencephalitis (EPM) caused by Sarcocystis neurona. It may also be used to treat other protozoal parasites such as Toxoplasma spp, coccidia, and Neospora caninum.
While it is labeled for use in horses, it is also used in cats, dogs, rabbits, birds, and reptiles to treat protozoal parasites ‘off label’ or ‘extra label’. Many drugs are commonly prescribed for off label use in veterinary medicine. In these instances, follow your veterinarian’s directions and cautions very carefully as their directions may be significantly different from those on the label.
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.