Comparison of trimethoprim-sulfamethoxazole, dapsone, and pentamidine in the prophylaxis of Pneumocystis carinii pneumonia.

STUDY OBJECTIVE: To compare the incidence of Pneumocystis carinii pneumonia (PCP) in patients infected with the human immunodeficiency virus (HIV) receiving one of three prophylactic agents.

DESIGN: Retrospective chart review.

SETTING: A university-affiliated Department of Veterans' Affairs medical center HIV clinic.

PATIENTS: All 200 HIV-infected patients enrolled in the clinic who were prescribed a PCP prophylactic drug during 18 months.

INTERVENTIONS: Patients were administered oral trimethoprim-sulfamethoxazole (TMP-SMX) DS, oral dapsone, or aerosolized pentamidine in a heirarchic fashion. A subset of 110 patients received only one of the prophylaxis regimens for at least 6 months; they were examined separately for the purpose of statistical analysis.

MEASUREMENTS AND MAIN RESULTS: One case of PCP was diagnosed in 1110 patient-months of oral TMP-SMX DS therapy, 6 in 418 patient-months of oral dapsone therapy, and 3 in 164 patient-months of aerosolized pentamidine therapy. In the subset population, the documented incidence of PCP was 0% among 71 TMP-SMX DS-treated patients, 16% among 25 dapsone-treated patients (p < 0.004), and 14% among 14 aerosolized pentamidine-treated patients (p < 0.03). For patients receiving primary prophylaxis, the incidence of PCP was 0% for 58 receiving TMP-SMX, 15% for 20 receiving dapsone (p = 0.015), and 17% for 6 receiving pentamidine (p = 0.094).

CONCLUSION: We believe TMP-SMX DS was more effective than oral dapsone or aerosolized pentamidine in preventing PCP in these HIV-infected patients.