Isospora belli Infection: Treatment with Pyrimethamine

Abstract
Isosporiasis is an uncommon but important diarrheal disease of humans that, like cryptosporidiosis, is life-threatening in patients with the acquired immunodeficiency syndrome (AIDS). Isospora belli infection responds rapidly to therapy with trimethoprim-sulfamethoxazole, but patients with AIDS have a high rate of adverse reactions to this therapy. The cases of two patients with AIDS, sulfonamide allergy, and I belli infection are reported. They were treated successfully with pyrimethamine alone, 75 mg/d, and recurrence was prevented with daily pyrimethamine therapy, 25 mg/d. In patients with AIDS with sulfonamide allergy or intolerance, pyrimethamine alone seems to be a reasonable alternative therapy for I belli infection.