The first FDA-approved treatment for EPM


Equine Protozoal Myeloencephalitis (EPM) is a progressive, degenerative disease of the central nervous system of the horse. The disease may be characterized by asymmetrical ataxia with or without muscle atrophy. There are several diseases of the central nervous system that can mimic EPM. It is important for the veterinarian to do a thorough neurological examination with appropriate laboratory diagnostic support such as a serum or cerebrospinal (CSF) analysis. Early, accurate diagnosis and prompt treatment offer the best chance for success.


Stopping an EPM Infection

Horses showing signs of EPM should be correctly diagnosed and be treated immediately. Treatment needs to begin quickly to stop the development of further permanent damage.1

Ponazuril, the active ingredient in Marquis®, crosses the blood/brain barrier2 to reach the central nervous system where it kills the parasite.3 The mechanism of action of Ponazuril is to disrupt intracellular pathways important in energy metabolism as well as cell division of the protozoan parasite.4 It does not target pathways of vertebrate cells as do some compounded products.


Marquis® is Safe to Use

Marquis® is safe to use in EPM compromised horses because it causes few adverse effects.* The results of safety studies suggest that ponazuril has minimal toxic potential when dosed at levels up to six times the recommended clinical dosage and for up to twice the recommended duration.5


Easy to Administer Accurately

Marquis® is an oral antiprotozoal paste packaged with four syringes and a precalibrated plunger. When the paste is administered orally, the horse receives the correct dosage. Medications that are top-dressed on the horse's feed can be spilled or dropped and the horse does not receive the full dose.

Marquis® is the first FDA-approved EPM treatment for horses.


*In animal safety studies, loose feces, sporadic inappetence, lost weight, and moderate edema in the uterine epithelium were observed.
Federal law restricts this drug to use by or on the order of a licensed veterinarian. For use only in horses. Do not use in horses intended for food.


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1 Reed S. Neurology is Not a Euphemism for Necropsy: A Review of Selected Neurologic Diseases Affecting Horses, Precedings 54th Annual Conf AAEP, Dec 2008, San Diego CA, pg 78.

2 Furr, M., Kennedy, T.: Pharmacokinetics of Ponazuril in Normal Horses. Study 150-717 Bayer Corporation.

3 Lindsay DS, Dubey JP, Kennedy TJ. Determination of the Activity of Ponazuril against Sarcocystis neurona in Cell Cultures. Vet Parasit 92 (2000); 165-169.

4 Hacksten JH et al; Parasitic apicomplexans harbor a chlorophyll a-D1complex, the potential target for therapeutic triazines. Parasitol Res 81; 1995; pg 207-216.

5 Kennedy T, Campbell J, Selzer V. Safety of Ponazuril 15% Oral Paste in Horses. Veterinary Therapeutics. Vol. 2, No.3, Summer 2001.


Marquis is a registered trademark of Bayer.

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