It is hypothesized that the maximum AZT antiretroviral effect, which occurs at 8 weeks of therapy, will be enhanced by 2 weeks of foscarnet treatment, given at the same time by intermittent intravenous infusion. In addition, the further lowering of serum p24 antigen concentration that should occur during combined therapy might continue when oral AZT therapy is continued without foscarnet.

There is a 4-week prestudy monitoring period during which AZT alone is administered on an outpatient basis, followed by a 2-week study period during which both intravenous foscarnet and oral AZT are administered in the hospital. During the subsequent 6-month follow-up period, oral AZT is administered and patients receive clinical evaluations. AZT is held for 48 hours on days before hospitalization and for 24 hours at the end of the hospitalization.

Inclusion Criteria

Concurrent Medication:

Allowed:

Medication necessary for the patient's welfare at the discretion of the investigator.

Patients must have the following:

• Received zidovudine (AZT) 200 mg every 4 hours (q4h) continuously for 8 - 16 weeks without Grade 3 or higher toxicity.
• Detectable p24 antigen in serum on at least 2 occasions during the prestudy period. All serum p24 antigen concentrations measured during the prestudy period must be at least twice the concentration cutoff value of the assay.
• Capability of giving informed consent.
• Per amendment of 890721, patients must enter the study period by September 30, 1989.

Exclusion Criteria

Co-existing Condition:

Patients with the following will be excluded:

• A history of hypersensitivity reaction to foscarnet or zidovudine (AZT).
• History of Grade 3 or 4 toxicity with AZT.
• Current Grade 2 or higher AZT toxicity.
• Osteomalacia, neoplasm metastatic to bone, or other known bone disease.
• Active opportunistic infection requiring myelosuppressive or nephrotoxic therapy.

Concurrent Medication:

Excluded:

• Antimetabolites.
• Immunomodulators.
• Nephrotoxins.
• Antiviral therapy.
• Myelosuppressive or nephrotoxic therapy.
• Acetaminophen.

Patients with the following will be excluded:

• A history of hypersensitivity reaction to foscarnet or zidovudine (AZT).
• History of Grade 3 or 4 toxicity with AZT.
• Current Grade 2 or higher AZT toxicity.
• Osteomalacia, neoplasm metastatic to bone, or other known bone disease.
• Active opportunistic infection requiring myelosuppressive or nephrotoxic therapy.