TRIMETHOPRIM-SULFAMETHOXAZOLE APPEARS MORE EFFECTIVE THAN AEROSOLIZED PENTAMIDINE AS SECONDARY PROPHYLAXIS AGAINST PNEUMOCYSTIS-CARINII PNEUMONIA IN PATIENTS WITH AIDS

Objective: We compared the efficacies of low-dose trimethoprim-sulphamethoxazole (TMP-SMX; one tablet: TMP, 160 mg, SMX, 800 mg, twice daily, twice a week) and aerosolized pentamidine (300 mg every 4 weeks) as secondary prophylaxis against Pneumocystis carinii pneumonia (PCP) in patients with HIV infection. Design: A retrospective controlled study. Setting: The study was performed at St Vincent's Hospital, Sydney, Australia, which is a tertiary referral university hospital. Patients, participants: Over a 4-year period, following primary episodes of PCP, 60 patients received TMP-SMX and 73 aerosolized pentamidine. Thirty-eight patients who received no secondary prophylaxis served as historical controls. Main outcome measures: The rate of and time to PCP relapse was recorded for patients receiving low-dose TMP-SMX, aerosolized pentamidine, or no prophylaxis. Results: Only one (1.7%) patient in the TMP-SMX-treated group relapsed, compared with 31 (42.5%) of those in the aerosolized pentamidine group and 21 (55.1%) of those in the control group (P < 0.0001). Median PCP-free survival times were > 1153 days in the TMP-SMX group, 496 days in the pentamidine group, and 265 days in the control group (P < 0.0001 between all groups). The rate of or time to relapse was not influenced by CD4+ lymphocyte count at the start of prophylaxis, primary, therapy, of PCP, history of allergy to TMP-SMX, or zidovudine therapy during the period of secondary prophylaxis in any patient group. Both therapies were well tolerated, with three (5%) of those receiving TMP-SMX and four (5%) of those receiving pentamidine discontinuing therapy as a result of side-effects. Conclusions: Low-dose TMP-SMX appears to be more effective compared with aerosolized pentamidine as secondary prophylaxis against PCP in HIV-infected patients. Zidovudine was well tolerated by both groups, but did not influence the rate of or time to relapse.