Preventing Pneumocystis carinii pneumonia in persons infected with human immunodeficiency virus.

Although the incidence of Pneumocystis carinii pneumonia (PCP) among adults infected with human immunodeficiency virus (HIV) has declined, no decline in PCP incidence has been observed among HIV-infected children, and PCP remains the most common serious opportunistic infection among both adults and children in the United States. Some evidence of airborne transmission of P. carinii exists, and some clusters of cases of PCP have been reported; however, data are insufficient to recommend that persons with PCP be separated from immunosuppressed persons as a standard practice. The incidence of PCP can be reduced substantially if persons at risk for PCP are identified and receive adequate chemoprophylaxis. Several drugs and drug combinations are highly effective in preventing PCP. For both adults and children, oral trimethoprim-sulfamethoxazole (TMP-SMZ) is the preferred form of prophylaxis. Adverse effects are commonly associated with the use of TMP-SMZ and in some cases may necessitate withdrawal of the drug until the effects resolve. However, reintroduction at the same dose or at a lower and gradually increasing dose will often permit the continued use of TMP-SMZ. For persons intolerant of TMP-SMZ, dapsone alone and dapsone plus pyrimethamine are effective alternatives. A third alternative is aerosolized pentamidine. Additional drugs of unproven efficacy but of potential use in exceptional cases are available.