A Randomized, Unblinded Trial of Zidovudine Versus ddC in the Treatment of Patients Status Post PCP Who Received Long-Term Zidovudine Therapy in Protocol ACTG 002

Inclusion Criteria Required: Prior zidovudine (AZT) therapy for 9 months. Concurrent Medication: Allowed: Chemoprophylaxis for Pneumocystis carinii pneumonia (PCP) with aerosolized pentamidine of 300 mg every 4 weeks through the Respirgard II nebulizer. Maintenance treatment with pyrimethamine, sulfadiazine, amphotericin, fluconazole, ketoconazole, acyclovir, or inhaled pentamidine for subjects who have recovered from toxoplasmosis, cryptococcosis, candidiasis, herpes infection, or PCP. Dapsone for PCP. Pyrimethamine-sulfadoxine for toxoplasmosis. Ganciclovir (DHPG) for maintenance only for cytomegalovirus (CMV) retinitis. Note: Any approved medications can be used to treat an opportunistic infection. All concurrent medications should be kept to a minimum and recorded. Patients must be positive for HIV by ELISA test and must have been receiving zidovudine (AZT) therapy for at least 9 months and have received AZT within 90 days prior to entry into the study. Patients may be transfusion dependent as long as no more than 3 units of blood are needed in a 21-day period and the hemoglobin does not fall below 6.4 g/dl on two consecutive occasions despite the transfusions. Exclusion Criteria Concurrent Medication: Excluded: Antiretroviral study medications other than zidovudine (AZT) and biologic response modifiers. Corticosteroids and chronic aspirin. Cimetidine. Flurazepam. Indomethacin. Ranitidine. Probenecid. Other experimental medications. Patients will be excluded from the study for the following reasons: Removal from zidovudine (AZT) during treatment on ACTG protocol 002 for recurrent grade 4 toxicity. Removal from prior dideoxycytidine (ddC) therapy for peripheral neuropathy = or > grade 3. Visceral or extensive Kaposi's sarcoma requiring therapy or another malignancy requiring therapy. Toxicity grades according to NIAID Recommendations for Grading Acute and Subacute Toxic Effects (Adults). Prior Medication: Excluded: Antiretroviral study medications other than zidovudine (AZT) and biologic response modifiers. Patients may not have visceral or extensive Kaposi's sarcoma requiring therapy or another malignancy requiring therapy.