Low-dose intermittent trimethoprim-sulfamethoxazole for prevention of Pneumocystis carinii pneumonia in patients with human immunodeficiency virus infection.

The important role of chemoprophylaxis for the prevention of Pneumocystis carinii pneumonia (PCP) in human immunodeficiency virus type 1 (HIV)-infected patients is undisputed. The most cost-effective regimen, however, is unknown. We reviewed our experience at two hospitals in the New York City area in which low-dose, intermittent therapy with the combination of trimethoprim and sulfamethoxazole was used to prevent PCP in HIV-infected patients. During a total of 202 months of primary prophylaxis in 32 patients and 319 months of secondary prophylaxis in 35 patients, PCP was diagnosed only once. More than 80% of patients were receiving zidovudine concomitantly. Adverse reactions to trimethoprim-sulfamethoxazole occurred in 31% and 52% of those receiving primary or secondary prophylaxis, respectively. When those patients who were considered ineligible to receive trimethoprim-sulfamethoxazole prophylaxis (principally based on a prior adverse drug reaction) are also factored in, then approximately 50% of HIV-infected patients are candidates for long-term trimethoprim-sulfamethoxazole prophylaxis. The projected cost savings of this prophylaxis regimen, compared with those currently recommended by the US Public Health Service, are enormous.