To compare the efficacy and safety of dapsone versus atovaquone in preventing or delaying the onset of histologically proven or probable Pneumocystis carinii pneumonia in HIV-infected patients with CD4 counts <= 200 cells/mm3 or <= 15 percent of the total lymphocyte count who are intolerant to trimethoprim and/or sulfonamides.

Trimethoprim/sulfamethoxazole (TMP/SMX), which is effective for secondary PCP prophylaxis, is associated with allergic manifestations and side effects that limit its use. Patients who are intolerant of TMP/SMX require an effective alternative. Dapsone and atovaquone have both shown promise as PCP prophylactic agents.

Trimethoprim/sulfamethoxazole (TMP/SMX), which is effective for secondary PCP prophylaxis, is associated with allergic manifestations and side effects that limit its use. Patients who are intolerant of TMP/SMX require an effective alternative. Dapsone and atovaquone have both shown promise as PCP prophylactic agents.

Patients are randomized to receive either dapsone or atovaquone daily, with follow-up at the clinic every 4 months.

Inclusion Criteria

Concurrent Medication: Strongly recommended:

• Pyrimethamine (50 mg) and folinic acid (15 mg) weekly in patients receiving dapsone who have CD4 count < 100 cells/mm3 and are toxoplasmosis seropositive.

Patients must have:

• Working diagnosis of HIV infection.
• CD4 count <= 200 cells/mm3 or <= 15 percent of total lymphocyte count at any time in the past OR a history of PCP.
• History of intolerance of trimethoprim and/or sulfonamides that required permanent discontinuation.

NOTE:

• Pregnant patients are eligible at the clinician's discretion.

Prior Medication:

Allowed:

• Prior PCP prophylaxis.

Exclusion Criteria

Co-existing Condition:

Patients with the following symptoms or conditions are excluded:

• Active pneumocystosis.

Concurrent Medication:

Excluded:

• PCP prophylaxis (other than study drug) or any medication with potential anti-PCP activity.

Patients with the following prior conditions are excluded:

• Known treatment-limiting reaction to dapsone or atovaquone.