Phase II Randomized Open-Label Trial of Atovaquone Plus Pyrimethamine and Atovaquone Plus Sulfadiazine for the Treatment of Acute Toxoplasmic Encephalitis

Inclusion Criteria Concurrent Medication: Allowed: * Aerosolized pentamidine for PCP prophylaxis. PER AMENDMENT 4/3/96: * History of treatment limiting toxicity to pyrimethamine. Patients with a history of treatment limiting toxicity to both pyrimethamine and sulfonamides will be assigned to receive atovaquone plus clarithromycin. Patients must have: * Documented HIV infection or diagnosis of AIDS (except for CD4 count \< 200 cells/mm3). * Toxoplasmic encephalitis. * Ability to give informed consent or legal designee who could give consent. PER AMENDMENT 4/3/96: * NOTE - A history of treatment limiting toxicity to both pyrimethamine and sulfonamides will result in the patient being enrolled in the atovaquone plus clarithromycin arm. Exclusion Criteria Co-existing Condition: Patients with the following symptoms or conditions are excluded: * Coma. * Opportunistic infection that requires either acute or maintenance treatment with disallowed medications. * Any infections or neoplasms of the central nervous system other than Toxoplasma, HIV encephalopathy, or syphilis. * Unable to take oral study drugs. * Malabsorption (i.e., three or more episodes of diarrhea per day that has caused \>= 10 percent loss of body weight over the past 4 weeks). * Positive CSF or serum for Cryptococcus antigen or culture (a positive serum antigen only is acceptable, provided patient received prior antifungal therapy and is on maintenance, and the likelihood of recurrence is low). * Malign…