Low-dose co-trimoxazole for prevention of Pneumocystis carinii pneumonia in human immunodeficiency virus disease.

The efficacy and tolerability of low, intermittent doses of co-trimoxazole (160 mg trimethoprim and 800 mg sulfamethoxazole given Monday, Wednesday, Friday) for prophylaxis against Pneumocystis carinii pneumonia (PCP) was assessed retrospectively in 116 patients with the acquired immunodeficiency syndrome (AIDS) and AIDS-related complex at high risk of PCP. 92% were receiving concomitant zidovudine. 71 with previous episode(s) of PCP were followed a mean of 18.5 months (range 3-42). 45 without past PCP but with depletion of CD4 cells to less than 200/microliters were observed for a mean of 24.2 months (range 9-40). PCP did not develop in any patient on co-trimoxazole. 33 (28%) had side-effects, mainly rash, pruritus, and nausea. 15 discontinued co-trimoxazole, but only 11 (9%), who withdrew in the first month, were clearly drug-intolerant. Thus, low-dose, thrice weekly co-trimoxazole completely prevents AIDS-associated PCP, is cost-effective, and well tolerated by more than 85% of patients. Controlled comparisons of this regimen with other prophylactic agents are warranted.