A CONTROLLED TRIAL OF AEROSOLIZED PENTAMIDINE OR TRIMETHOPRIM SULFAMETHOXAZOLE AS PRIMARY PROPHYLAXIS AGAINST PNEUMOCYSTIS-CARINII PNEUMONIA IN PATIENTS WITH HUMAN-IMMUNODEFICIENCY-VIRUS INFECTION

Background. Primary prophylaxis against Pneumocystis carinii pneumonia (PCP) is recommended for patients with human immunodeficiency virus (HIV) infection if their CD4 cell counts are below 200 per cubic millimeter (0.2 x 10(9) per liter). Either aerosolized pentamidine or trimethoprim-sulfamethoxazole (co-trimoxazole) is commonly prescribed for prophylaxis, but the relative efficacy and toxicity of these agents are unknown.

Methods. We conducted a multicenter trial involving 215 HIV-infected patients with no history of PCP but with CD4 cell counts below 200 per cubic millimeter. The patients were randomly assigned to one of three regimens: aerosolized pentamidine once a month, 480 mg of trimethoprim-sulfamethoxazole once a day (80 mg of trimethoprim and 400 mg of sulfamethoxazole), or 960 mg of trimethoprim-sulfamethoxazole once a day (160 mg and 800 mg, respectively). The cumulative incidence of PCP was estimated by Kaplan-Meier survival analysis.

Results. After a mean follow-up of 264 days, 6 of the 71 patients in the pentamidine group had a confirmed first episode of PCP (11 percent), whereas none of the 142 patients in the two trimethoprim-sulfamethoxazole groups had PCP (P = 0.002). However, adverse events that required discontinuation of the medication were much more frequent in the trimethoprim-sulfamethoxazole groups (1 7 and 18 patients) than in the pentamidine group (2 patients). The adverse reactions occurred significantly sooner in the group given 960 mg of trimethoprim-sulfamethoxazole than in the group given 480 mg (mean time, 16 vs. 57 days; P = 0.02).

Conclusions. For patients with HIV infection, trimethoprim-sulfamethoxazole taken once a day is more effective as primary prophylaxis against PCP than aerosolized pentamidine administered once a month, although adverse drug reactions are more frequent with trimethoprim-sulfamethoxazole.