FDA Approves Loading Dose for EPM Treatment

It’s another day at the barn, but you notice your horse stumbling and not walking like he normally does. He also seems mildly depressed. Are these subtle signs of a neurological disease? Could it be equine protozoal myeloencephalitis (EPM)?

EPM is a neurological disease in horses caused by Sarcocystis neurona, a parasite that invades the brain and spinal cord. When undetected or untreated, EPM can cause serious damage to the horse’s central nervous system and in some cases be fatal.1 Opossums are definitive hosts for this parasite and horses become infected with EPM through contact with opossum feces by grazing or by eating contaminated feed.1

Thankfully, when it is time for horse owners to take action against this potentially deadly disease, there is MARQUIS® (15% w/w ponazuril), the first FDA-approved treatment for EPM.

The FDA recently approved giving a loading dose (a larger dose on the first day), of MARQUIS to begin the treatment.2 Administration of the loading dose allows MARQUIS concentrations to approach a steady state–when the rate of input is equal to the rate of elimination–within 1-2 days, as opposed to eight days using the originally approved dosage regimen.2

The MARQUIS syringe is calibrated for a single dose, based on the weight of the horse.3 On the first day of treatment, administer three doses (15 mg/kg body weight).2 Then continue 27 days of treatment at the maintenance dose (5 mg/kg body weight).2

Recovery from EPM can be successful if the horse receives prompt and proper treatment. Better outcomes seem to be associated with starting treatment early, with the most significant improvement generally seen within the first four weeks.4 MARQUIS is easy to administer, making it even easier for clients to deliver a precise dose. Delivery of the correct dosage is not dependent upon feed consumption. When treating for EPM, horse owners can be confident in choosing MARQUIS because of its FDA approval and accurate dosing.

Merial is a world-leading, innovation-driven animal health company, providing a comprehensive range of products to enhance the health and well-being of a wide range of animals. Merial employs 6,100 people and operates in more than 150 countries worldwide with over €2 billion of sales in 2014. Merial is a Sanofi company. For more information, please see www.merial.com.

The safe use of MARQUIS in horses used for breeding purposes, during pregnancy, or in lactating mares, has not been evaluated. In animal safety studies, loose feces, sporadic inappetence, lost weight, and moderate edema in the uterine epithelium were observed.

®MARQUIS is a registered trademark of Merial. ©2015 Merial, Inc. All rights reserved. EQUIOMQ1510 (08/15)

1. Reed S. Neurology is not a Euphemism for Necropsy: A Review of Selected Neurological Diseases affecting horses; AAEP Proceedings. 2008;78-109.
2. Freedom of Information Summary, Supplemental New Animal Drug Application. Available at: http://www.fda.gov/downloads/AnimalVeterinary/Products/ApprovedAnimalDrugProducts/FOIADrugSummaries/UCM449259.pdf. Accessed July 28, 2015.
3. MARQUIS product label.
4. McCoy A. Equine protozoal myeloencephalitis. University of Minnesota Extension. Available at: www.extension.umn.edu/agriculture/horse/health/equine-protozoal-myeloencephalitis. Accessed February 17, 2015.

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