The treatment of experimental toxoplasmosis in rabbits.

Sulphadimidine alone is of little value in treating experimental toxoplasmosis in rabbits, because most rabbits acetylate the drug very rapidly. Within a short time of dosing such animals, there is little or none of the uncombined drug in the blood. In rabbits which do not acetylate sulphadimidine rapidly, relatively high concentrations of the free sulphonamide can be attained in the blood: in such animals, toxoplasmosis responds to treatment with sulphadimidine. Sulphathiazole is not acetylated so rapidly and is effective even in rabbits which acetylate sulphadimidine quickly. Pyrimethamine, even in doses as high as 50 mg. three times daily, is ineffective; dapsone is effective.