The Safety and Effectiveness of Zidovudine Plus Adefovir in HIV-Infected Patients

Inclusion Criteria Concurrent Medication: Allowed: * Prophylactic therapy with aerosolized pentamidine, oral trimethoprim/sulfamethoxazole (Bactrim, Septra) or dapsone, and fluconazole or ketoconazole IF on a stable regimen for at least 4 weeks prior to study entry. Patients must have: * HIV seropositivity. * Mean CD4 count \<= 500 cells/mm3. * Been receiving AZT at 500 mg daily for at least 4 weeks prior to study entry. * Life expectancy of at least 3 months. NOTE: * Kaposi's sarcoma is permitted provided patient has not received any systemic therapy for KS within the past 4 weeks. Patients with a history of another malignancy must be disease free for 6 months or more prior to study entry. Exclusion Criteria Co-existing Condition: Patients with the following symptoms or conditions are excluded: * Inadequate venous access. * Active, serious infections (other than HIV infection) requiring parenteral antibiotic therapy. * Clinically significant cardiac disease, including symptoms of ischemia, congestive heart failure, or clinically significant arrhythmia. * Active malignancy other than Kaposi's sarcoma. * Mental incapacity or illness that may affect compliance. Concurrent Medication: Excluded: * ddI or ddC. * Interferon alpha. * Ganciclovir. * Foscarnet. * Diuretics. * Investigational agents including d4T. * Chemotherapeutic agents. * Amphotericin B. * Aminoglycoside antibiotics. * Other nephrotoxic agents. * Immunomodulatory agents. * Parenteral therapy for an active, serious infection (other than HIV infection). Prior Medication: Excluded within 2 weeks prior to study entry: * ddI or ddC. * Interferon alpha. * Ganciclovir. * Foscarnet. * Diuretics. * Investigational agents including d4T. * Chemotherapeutic agents. * Amphotericin B. * Aminoglycoside antibiotics. * Other nephrotoxic agents. * Immunomodulatory agents. Excluded within 4 weeks prior to study entry: Systemic therapy for Kaposi's sarcoma. Required: * AZT at a stable dose for at least 4 weeks prior to study entry. Current use of illicit drugs (e.g., heroin or cocaine). Ingestion of substantial alcohol.