Treatment of Pneumocystis carinii pneumonia with trimethoprim-sulfamethoxazole and pentamidine: efficacy and toxicity.

A 39-year-old man with Pneumocystis carinii pneumonia responded poorly to oral trimethoprim-sulfamethoxazole (TMP-SMX) therapy, despite excellent serum concentrations of the drug. He developed severe thrombocytopenia when pentamidine was added to the regimen. This case illustrates problems of drug efficacy and toxicity in the treatment of P carinii pneumonia and suggests caution in the use of TMP-SMX and pentamidine in combination.