A Double-Blind, Randomized Parallel Group Study Comparing Procysteine to Placebo in HIV-Infected Patients Who Are Taking Antiretroviral Nucleosides

Inclusion Criteria Concurrent Medication: Required: Antiretroviral nucleosides (AZT alone, ddI alone, AZT plus ddI, or AZT plus ddC). Regimen may be altered on or after Week 16. Allowed: * Appropriate topical treatment or local radiotherapy for KS. * Treatment or prophylaxis for opportunistic infections, including pentamidine, cotrimoxazole, acyclovir, fluconazole, etc., at the discretion of the investigator. Patients must have: * Documented serologic evidence confirming HIV infection. * Ability to participate in an outpatient study for at least 26 weeks. * Either: * (a) diagnosis of AIDS or AIDS-Related Complex (ARC) with CD4 count of 50 - 300 cells/mm3, or (b) CD4 count of 50 - 200 cells/mm3 and no symptoms of AIDS (asymptomatic). (Note: * Patients whose AIDS-defining condition is Kaposi's sarcoma alone must have CD4 count of 50 - 200 cells/mm3.) Exclusion Criteria Co-existing Condition: Patients with the following symptoms or conditions are excluded: * Evidence of organ involvement with CMV and/or positive blood cultures for Mycobacterium avium. * Life expectancy less than 26 weeks. * Malignancy or advancing Kaposi's sarcoma (KS) with advancing or unstable skin lesion, or known or suspected visceral disease which requires systemic cytotoxic, myelosuppressive chemotherapy. * Stage 2 or greater AIDS-dementia complex (ADC), defined as ability to perform basic activities of self-care but inability to work or maintain more demanding aspects of daily life as a result of an acquired decrease in cognitive CNS-related motor function characteristic of ADC. * Psychological or emotional problems that prevent adequate compliance with study therapy. Concurrent Medication: Excluded: * Daily Vitamin C dosage greater than 1,000 mg or daily Vitamin E dosage greater than 100 units. * N-acetylcysteine, cysteine, or glutathione. * Any investigational drug. * Systemic chemotherapy. Patients with the following prior conditions are excluded: * History of organ involvement with cytomegalovirus (CMV) and/or positive blood cultures for Mycobacterium avium. * Intractable diarrhea, defined as greater than 4 bowel movements per day for at least 2 weeks. * History of seizures which have not been controlled with appropriate anticonvulsant medications within the previous 6 months. Prior Medication: Excluded: * Any investigational agent or biological response modifier (including interferon or corticosteroids) within 1 month of study entry. * Use of erythropoietin (EPO), G-CSF, or GM-CSF within 28 days of randomization. Risk Behavior: Excluded: Active alcohol or drug abuse. Required: Antiretroviral nucleosides (AZT alone, ddI alone, AZT plus ddI, or AZT plus ddC) for at least 3 months prior to study entry.