Effects of sulfonylurea compounds on Pneumocystis carinii.

Two sulfonylurea compounds, carbutamide and tolbutamide, were studied for efficacy against Pneumocystis carinii pneumonitis in the corticosteroid-treated rat model and compared with trimethoprim-sulfamethoxazole (TMP-SMZ). The chemical structures of these sulfonylureas are identical except that an amino group in carbutamide is replaced with a methyl group in tolbutamide. Carbutamide was totally effective in the prevention and treatment of P. carinii pneumonitis in dosages of 100 and 200 mg/kg per day. The carbutamide dosage of 50 mg/kg per day prevented the infection in 90% of animals, whereas tolbutamide in the same dosage permitted infection in 100% of animals. This study shows that carbutamide is at least as effective as TMP-SMZ in the treatment and prevention of murine P. carinii pneumonitis. The presence of an amino group in the para position on the benezene ring is a determinant for this activity.