On Nov. 19 the U.S. Food and Drug Administration (FDA) approved Navigator for treating equine protozoal myeloencephalitis (EPM). This drug has been under development for more than six years.

IDEXX Laboratories of Westbrook, Maine, received approval for the 32% nitazoxanide antiprotozoal oral paste designed to kill the single-celled protozoan parasite Sarcocystis neurona, which causes EPM. (Read more on EPM at www.TheHorse.com/epm.)

Navigator is the second FDA-approved EPM treatment to hit the equine market; Bayer’s Marquis was the first to be launched (August 2001).

The treatment regimen lasts 28 days, and it begins with five days of half-strength doses. This provides “a more gradual kill” of the parasite to allow intestinal microflora to adjust to the drug, and minimize the transient neurological worsening sometimes seen with extreme immune system stimulation (by numerous dead parasites), said Dorsey Kordick, PhD, of IDEXX. The horse should receive one dose daily, just before receiving his grain. Navigator’s cost to veterinarians should be comparable to other EPM treatments, she said