Saturday, January 15, 2011

New Product: Protazil

Protazil (diclazuril) was just released this month for the treatment and/or prevention of EPM (Equine Protozoal Myelitis) in horses. EPM is a disease that has been has been around for several decades. The disease is caused by a protozoa, called Sarcocystis neurona. It primarily causes neurologic deficits, which are sometimes vague and non-specific. This is not the first or only drug available for the treatment of this disease. It has actually been around for a while. Prior to its adaptation to the horse it was used to treat protozoal infections in chickens. While it is nice to have another weapon in the war on EPM, this drug is not going to cure every horse. According to the information submitted to the FDA for approval, only 67% of affected horses improved one neurologic grade (graded on a scale of 1-5) or no longer tested positive. That means that a horse that has grade 3 neurologic deficits has a 67% chance of improving to a grade 2. Meaning the horse still has neurologic deficits, they just might not be as bad. One of the challenges with this data is that they only looked at the horses a month after treatment stopped. They likely continued to improve beyond that time frame. The neurologic system is very slow to heal, to the extent that it can. Neurologic deficits associated with EPM can be caused by direct damage of the protozoa to the spinal cord and by the inflammation associated with their presence. Killing the protozoa does nothing to fix the damage that the protozoa did prior to starting treatment. Thus, at least so far, all the medications currently used to treat EPM, while they may be effective at killing the protozoa, do not always result in complete resolution of the symptoms. Initiating treatment as soon as possible, while any neurologic deficits are mild, will result in the best clinical outcomes. If treatment is not started until the horse has severe neurologic deficits, the deficits may improve, but in the end the horse will be less likely to experience a complete resolution of symptoms. Like most new drugs, this stuff is not cheap. A 28 day course of treatment will cost somewhere around $850.

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