Inclusion Criteria

Patients must have:

• Diagnosis of AIDS or AIDS related complex (ARC).
• Previous intolerance to daily doses of up to 1200 mg of zidovudine (AZT) demonstrated by a decrease in hemoglobin levels of 2 - 8.5 g/dl or AZT-related depression of neutrophils of 200 - 750 cells/mm3.
• Ability to provide informed consent.

Prior Medication:

Allowed:

• Zidovudine (AZT).

Exclusion Criteria

Co-existing Condition:

Patients with the following are excluded:

• AIDS-defining opportunistic infection on enrollment.
• Intractable diarrhea.
• History of seizures within past 2 years or currently requiring anticonvulsants for control.
• Any other clinical conditions or prior therapy which in the opinion of the investigator would make the patient unsuitable for study or unable to comply with the dosing requirements.

Concurrent Medication:

Excluded:

• Systemic maintenance or chemoprophylaxis for opportunistic infection (includes dapsone, acyclovir).
• Systemic therapy with this or any other antiretroviral drug (except zidovudine (AZT)) or investigational drug.
• Ribavirin.
• Cytotoxic anticancer therapy.
• Any agent known as a potent inducer or inhibitor of drug-metabolizing enzymes (includes rifampin and barbiturates).
• Trimethoprim / sulfamethoxazole (TMP / SMX).

Patients with the following are excluded:

• AIDS-defining opportunistic infection on enrollment.
• Intractable diarrhea.
• History of seizures within past 2 years or currently requiring anticonvulsants for control.
• Any other clinical conditions or prior therapy which in the opinion of the investigator would make the patient unsuitable for study or unable to comply with the dosing requirements.

Prior Medication:

Excluded within 2 weeks of study entry:

• Any agent known as a potent inducer or inhibitor of drug-metabolizing enzymes (includes rifampin and barbiturates).

Excluded within 1 month of study entry:

• Systemic therapy with this or any other antiretroviral drug (except zidovudine (AZT)) or investigational drug.

Excluded within 3 months of study entry:

• Ribavirin.
• Cytotoxic anticancer therapy.

Active alcohol or drug abuse sufficient in investigator's opinion to prevent adequate compliance with study therapy.