Inclusion Criteria

Concurrent Medication:

Required:

• Prophylactic treatment for Pneumocystis carinii pneumonia with aerosolized pentamidine, dapsone, or trimethoprim / sulfamethoxazole.

Allowed:

• Most medications not specifically excluded.

Prior Medication:

Allowed:

• Antivirals.
• Antiretrovirals.

Patients:

• Must be HIV positive or have an AIDS-defining illness OR be at known risk for HIV infection and have a CD4 cell count < 200/mm3 and no other known immunosuppressive disease.
• Must have positive titer for Toxoplasma gondii.
• Must be or become a patient of a CPCRA physician.
• May participate in other clinical trials as long as there is no potential activity against Toxoplasma gondii or cross-toxicity among study drugs.

Exclusion Criteria

Co-existing Condition:

Patients with the following conditions or symptoms are excluded:

• History of ocular, pulmonary, or central nervous system (CNS) toxicity.
• CNS lesions.
• Neurologic deficits except peripheral neuropathy.
• Mild, moderate, severe, or end-stage AIDS dementia complex. Grade 3 or higher nausea and/or vomiting.
• Sensitivity to pyrimethamine.

Concurrent Medication:

Excluded:

• On-going therapy with clindamycin, fansidar, methotrexate, trimetrexate, spiramycin, azithromycin, clarithromycin, 566C80, and/or sulfa agents other than anti-PCP agents.

Patients with the following are excluded:

• History of ocular, pulmonary, or central nervous system (CNS) toxicity.
• CNS lesions or history of CNS lesions.
• Neurologic deficits except peripheral neuropathy.
• Mild, moderate, severe, or end-stage AIDS dementia complex. Grade 3 or higher nausea and/or vomiting.
• Sensitivity to pyrimethamine.