MONODRUG EFFICACIES OF SULFONAMIDES IN PROPHYLAXIS FOR PNEUMOCYSTIS-CARINII PNEUMONIA

A remarkably high rate of adverse events is associated with the use of trimethoprim-sulfamethoxazole in patients with human immunodeficiency virus type 1 infection, We examined the efficacies of sulfonamides al one in the prevention of Pneumocystis carinii pneumonitis, with the as sumption that at least some of the adverse events with the drug combin ation might be due to trimethoprim. With the immunosuppressed rat mode l, eight sulfonamides were studied at 100, 10, and 1.0 mg/kg/day (10 r ats per dosage and drug), P, carinii infection was prevented in all an imals (100%) receiving dosages of as little as 1.0 mg of sulfamethoxaz ole, sulfamethoxy-pyridazine, and sulfadimethoxine per kg per day, as little as 10 mg of sulfameter, sulfachlorpyridazine, and sulfaquinoxal ine per kg per day; and 100 mg of sulfaguanidine and sulfanilamide per kg per day, These studies suggest that a sulfonamide, such as sulfame thoxazole, might provide effective prophylaxis for P. carinii pneumoni tis without trimethoprim.