Primary prophylaxis for Pneumocystis carinii pneumonia

Abstract

To compare the efficacy and tolerance of monthly aerosolized pentamidine versus cotrimoxazole versus dapsone plus pyrimethamine to prevent the initial episodes of Pneumocystis carinii pneumonia (PCP) in HIV-infected patients. An open randomized clinical trial. HIV-infected patients (n = 331) with CD4 cell counts < 200 x 10(6)/l or with AIDS but without a history of PCP or cerebral toxoplasmosis (CT) were randomized to receive pentamidine (300 mg every 4 weeks), cotrimoxazole (160/800 mg 3 days a week) or dapsone plus pyrimethamine (100 and 25 mg weekly). If immunoglobulin G (IgG) antibodies to Toxoplasma were present, patients in the first two groups were randomized further to 25 mg pyrimethamine per week or to no treatment. The mean follow-up was 313 days (range, 30-670 days). The three groups were homogeneous for age, sex, risk group for HIV infection, initial CD4 cell count and mean follow-up. PCP developed in 16 patients, with an estimated cumulative probability of 5.3% at 1 year of follow-up. The PCP rate per year of observation, using an intention-to-treat analysis, was 5.6% [95% confidence interval (CI), 0.9-10.3], 3% (95% CI, 0-6.3) and 8.3% (95% CI, 2.8-13.8) in the groups treated with pentamidine, cotrimoxazole and dapsone plus pyrimethamine, respectively (P > 0.05). Moderate or severe side-effects were observed in one patient on pentamidine, 10 on cotrimoxazole and nine on dapsone plus pyrimethamine (P < 0.05); the study drug had to be discontinued in no, 10 and six patients, respectively (P < 0.05). Neither cotrimoxazole alone nor pyrimethamine combined with dapsone or cotrimoxazole prevented initial episodes of toxoplasmosis among patients with IgG antibodies to Toxoplasma gondii. Low-dose thrice-weekly cotrimoxazole or weekly dapsone plus pyrimethamine was not significantly worse (differences > 15% would have been detected with 90% certainty) than monthly aerosolized pentamidine in preventing a first episode of PCP in patients at high risk, but aerosolized pentamidine was better tolerated.