Abstract: The present invention relates to compositions and methods for treating equines, such as horses, afflicted with equine protozoal myeloencephalitis or EPM. The therapeutic compositions comprise a combination of pyrimethamine and a sulfonamide, preferably, sulfadiazine, in the absence of known therapeutic amounts of trimethoprim.

Abstract: The present invention relates to pharmaceutical compositions for the sustained release of pharmacologically active compounds, and methods of their manufacture and use. The pharmaceutical compositions contain microcrystals of pharmacologically active compounds which are encapsulated within a phospholipid layer which contain a unique combination of phospholipids. The pharmaceutical compositions may be rendered suitable for injection. The microcrystals are of varying sizes. At least 50 percent of the microcrystals are from 0.5 &mgr;m and 3.0 &mgr;m in diameter, at least ten percent of the microcrystals are from 3.0 &mgr;m to 10 &mgr;m in diameter, and the composition may contain microcrystals which are greater than 10 &mgr;m in diameter. Methods of manufacturing the composition are disclosed, as well as various methods of administration.