Crossover of Human Immunodeficiency Virus-infected Patients from Aerosolized Pentamidine to Trimethoprim-sulfamethoxazole: Lack of Hematologic Toxicity and Relationship of Side Effects to CD4+ Lymphocyte Count

Trimethoprim-sulfamethoxazole (TMP/SMZ) was given in a crossover study to 130 human immunodeficiency virus-infected patients who had been receiving aerosolized pentamidine; 86 (66%) successfully crossed over to TMP/SMZ without hypersensitivity reactions or hematologic toxicity. No significant changes occurred in mean hemoglobin concentration, leukocyte count, or platelet count between study enrollment and 12-month follow-up. Predominant side-effects, in 41 patients (33.8%), were fever and maculopapular rashes, which resolved promptly with discontinuation of TMP/SMZ. The mean time to first side effect was 12.3 days, and 86% of side effects developed within 30 days. Three patients experienced toxicity serious enough to warrant hospitalization. Of patients with < or = 200 CD4+ lymphocytes/mm3, 57% developed rashes after the cross-over compared with only 27% of patients with higher CD4+ cell counts. Many patients currently receiving aerosolized pentamidine can be safely crossed over without hematologic toxicity or hypersensitivity reactions.