To evaluate the safety and tolerance, in patients with severe clinical manifestations of HIV infection, of zidovudine (AZT) administered daily for 48 weeks as a low dose every 4 hours or a higher dose every 12 hours.

Inclusion Criteria

Concurrent Medication:

Allowed:

- Prophylaxis or treatment for Pneumocystis carinii pneumonia (PCP) consisting of either trimethoprim / sulfamethoxazole, aerosolized pentamidine, pyrimethamine / sulfadoxine, or dapsone allowed at the discretion of the investigator.

Patients with the following are excluded:

• Any immediately life-threatening infection or medical condition present at the time of study entry.
• Any active opportunistic or other infection requiring chronic therapy at the time of study entry. Patients with PCP may be randomized to study medication following a minimum 7-day course of therapy resulting in stabilization of their disease. Patients with stabilized disease must have a fever < 39 C for at least 48 hours, pO2 (on room air ) = or > 60 mm, and an Arterial/alveolar gradient = or < 30 mm.
• Diagnosis of AIDS Dementia Complex.
• Received more than 4 weeks of antiretroviral therapy or who previously discontinued antiretroviral therapy due to drug related toxicity.
• Diseases and conditions listed in Exclusion Co-existing Conditions.

Patients must have the following:

• Seropositive for HIV infection documented by any federally licensed ELISA and confirmed by Western blot.
• Advanced HIV disease or AIDS-related complex.
• Ability to give informed consent.

Exclusion Criteria

Co-existing Condition:

Patients with the following conditions or symptoms are excluded:

• AIDS with malignant disease likely to require cytotoxic chemotherapy.
• Diagnosis of AIDS Dementia Complex.
• Impaired renal function ( Creatinine clearance < 50 ml/min/1.73m2 or serum creatinine = or > 2 mg/dl).
• Impaired hepatic function ( ALT = or > 5 x upper limit of normal).
• Fever > 39 C at entry.

Concurrent Medication:

Excluded:

• Any other experimental therapy.
• Drugs which cause significant bone marrow suppression.
• Cytolytic chemotherapy.
• Drugs which cause significant nephrotoxicity or hepatotoxicity.

Concurrent Treatment:

Excluded:

• Radiation therapy (with the exception of electron beam therapy to an area < 100 cm2).

Prior Medication:

Excluded within 2 weeks of study entry:

- Any other experimental therapy. Drugs which cause significant bone marrow suppression. Cytolytic chemotherapy. Drugs which cause significant nephrotoxicity or hepatotoxicity.

Excluded within 4 weeks of entry:

- Immunomodulating agents, including pharmacological doses of steroids for more than 10 days (except for management of severe PCP in which case duration should not exceed 21 days). Interferon. Isoprinosine. IL-2.

Excluded within 8 weeks of entry:

-

Antiretroviral agents including:

- Ribavirin. Dideoxycytidine (ddC). Dideoxyadenosine (ddA). Didanosine (ddI). Foscarnet. Dextran Sulfate. AL-721. Retrovir (Zidovudine, AZT) for greater than 4 weeks or within 90 days of study entry, or patients who originally discontinued Retrovir due to drug-related toxicity. Drugs metabolized by hepatic glucuronidation may alter the metabolism of Retrovir and should not be used chronically.

Prior Treatment:

Excluded:

• Radiation therapy (with the exception of electron beam therapy to an area < 100 cm2) within 2 weeks of study entry.

Known active drug or alcohol abuse.