To determine the change in CD4 count after 4 and 8 weeks in HIV-infected patients treated with cimetidine compared to placebo. To observe time-associated trends at weeks 4, 8, 12, and 16 in the change of CD4 counts for patients taking cimetidine for the full 16 weeks. To establish a safety record for cimetidine use in HIV-positive patients.

Inclusion Criteria:

Concurrent Medication:

Allowed:

• All FDA-approved medications, antiretrovirals, and PCP prophylaxis drugs, with the exception of warfarin (Coumadin).
• Other self-prescribed medications available either over the counter or through buyer's clubs.

Patients must have:

HIV positivity.

NOTE:

• Patients on an antiviral or immunomodulating drug must have received it for at least 2 months and have no intention to make clinical or therapeutic changes in the first 8 weeks (such as adding a new agent or discontinuing effective viral suppressive therapy) that may interfere with the study.

NOTE:

• Patients who become pregnant after enrollment will be permitted to continue on study drug but must sign an additional informed consent indicating their awareness of the issues in taking a drug with limited safety data during pregnancy.

Prior Medication:

Allowed:

• Antiviral and immunomodulating drugs, provided patient has been on such therapy for at least 2 months prior to study entry.

Exclusion Criteria:

Co-existing Condition:

Patients with the following symptoms or conditions are excluded:

• Known intolerance or hypersensitivity to cimetidine.
• Evidence of active opportunistic infection or malignancy requiring high-dose systemic chemotherapy.
• Any symptoms suggestive of concurrent illness that are not attributable to overall impairment by HIV or are not diagnosable based on the available evidence.
• Inability to swallow tablets (gastric feeding tubes are allowed).
• Not willing to comply with visit schedule and study procedures.

Concurrent Medication:

Excluded:

• Warfarin (Coumadin).

Prior Medication:

Excluded within 4 weeks prior to study entry:

• cimetidine (Tagamet), ranitidine (Zantac), famotidine (Pepcid), and nizatidine (Axid).