A Study of Pyrimethamine in the Treatment of Infection by a Certain Parasite in HIV-Positive Patients

Inclusion Criteria Concurrent Medication: Allowed: Aerosolized pentamidine for Pneumocystis carinii pneumonia prophylaxis. Isoniazid not initiated during study period. Methadone maintenance. Required: Stable prescribed dose of zidovudine (AZT) of at least 500 mg/day. Exclusion Criteria Co-existing Condition: Patients with the following conditions or symptoms are excluded: Prior history of toxoplasmic encephalitis. Unable to take oral medication reliably or have a malabsorption syndrome (i.e., 3 or more loose stools/day for at least 4 weeks associated with an unintentional weight loss of = or > 10 percent of body weight). History of sensitivity to the study medications. Concurrent Medication: Excluded: Maintenance therapy for opportunistic infections with macrolides or sulfonamides, immunomodulators, rifampin, amphotericin, dapsone, ganciclovir, antifolates, probenecid, benzodiazepines, nephrotoxins, and experimental cytotoxic chemotherapy. Medications such as aspirin, benzodiazepines, cimetidine, indomethacin, morphine, and sulfonamides should be avoided. Concurrent Treatment: Excluded: Lymphocyte replacement. Patients with the following are excluded: Any medical or social condition that, in the opinion of the investigator, would adversely affect either participation or compliance in the study. Diagnosis of AIDS and febrile and have evidence of another serious opportunistic infection or central nervous system impairment. Prior Medication: Excluded: Maintenance therapy for opportunistic infections with macrolides or sulfonamides, immunomodulators, rifampin, amphotericin, dapsone, ganciclovir, antifolates, probenecid, benzodiazepines, nephrotoxins, and experimental cytotoxic chemotherapy within past 14 days. Prior Treatment: Excluded: Lymphocyte replacement within past 14 days. Patients have the following symptoms and conditions: Laboratory evidence of HIV infection. Serological evidence of exposure to Toxoplasma gondii, but no clinical evidence of active toxoplasmic infection. Able to understand and sign a written informed consent. Either homosexual male or intravenous drug user. Required: Stable prescribed dose of zidovudine (AZT) of at least 500 mg/day for 4 weeks. Intravenous drug abuse.