Prophylaxis of Pneumocystis carinii pneumonia in patients infected with the human immunodeficiency virus type 1.

Immunosuppression due to human immunodeficiency virus type 1 (HIV) infection has led to a marked increase in Pneumocystis carinii pneumonia (PCP). Prophylaxis against PCP is standard practice in pediatric cancer patients but is associated with unique problems in HIV-infected patients, including the need for lifelong therapy, adverse reactions, and drug interactions. HIV-infected patients at highest risk for PCP are those with a prior episode of PCP and/or a CD4 lymphocyte count of less than 200 cells/microL. A combination of trimethoprim and sulfamethoxazole is effective prophylactically, although a significant rate of adverse reactions makes long-term prophylaxis difficult. Other oral medications such as dapsone and a combination of pyrimethamine and sulfadoxine are promising but not yet adequately tested. Inhalation of aerosolized pentamidine is an effective and safe means of prophylaxis if the proper dose and nebulizer are used. The only common adverse effects with the latter are airway irritation manifested by cough or wheezing. Zidovudine appears to have a synergistic benefit in further reducing the attack rate of PCP when used with aerosolized pentamidine.