A Phase I Randomized Dose/Formulation Comparison Study of SC-52151

Inclusion Criteria Concurrent Medication: Required for patients with CD4 count \<= 200 cells/mm3: * PCP prophylaxis using TMP/SMX or aerosolized pentamidine. Allowed: * Topical antifungal agents. * Up to 1000 mg/day acyclovir as maintenance therapy for herpes simplex virus. * Antibiotics for bacterial infections. * Antipyretics, analgesics, nonsteroidal anti-inflammatory agents, antiemetics, and methadone for symptomatic treatment. Patients must have: * HIV infection. * CD4 count 150 - 500 cells/mm3. Exclusion Criteria Co-existing Condition: Patients with the following symptoms or conditions are excluded: * Unable to tolerate the standard diet required for the study. * Unable to give informed consent. Concurrent Medication: Excluded: * Antiretrovirals and biologic response modifiers (including HIV vaccines). * Maintenance with ketoconazole, fluconazole, itraconazole, ganciclovir, foscarnet, pyrimethamine, sulfadiazine, clindamycin, azithromycin, isoniazid, rifampin, rifabutin, ethambutol, pyrazinamide, clofazimine, or clarithromycin. * Prophylaxis for Mycobacterial infection or fungal infections other than Candidiasis. * Allopurinol. * Omeprazole. * Astemizole. * Terfenadine. * Loratadine. * Psychotropics. * Phenylbutazone. * Barbiturates. * Benzodiazepines. * Monoamine oxidase inhibitors. * H-2 blockers. * Anticonvulsants. * Coumadin anticoagulants. * Oral contraceptives. * Antiarrhythmics. * Diltiazem. * Metronidazole. * Erythromycin. * Chloramphenicol. * Fluoroquinolones. * Disulfiram. * Erythropoietin. * G-CSF or GM-CSF. * Systemic corticosteroids. * Alcohol, including alcohol-containing medications. Patients with the following prior conditions are excluded: * Unexplained temperature \>= 38.5 C for any 7 days within the 30 days prior to study entry. * Chronic diarrhea (\>= three stools per day) for any 15 days within the 30 days prior to study entry. * Malignancy other than basal or squamous cell carcinoma of the skin, cervical intraepithelial neoplasia, and minimal Kaposi's sarcoma. Prior Medication: Excluded at any time: * Prior HIV protease inhibitor. Excluded within 30 days prior to study entry: * Investigational drugs. * Recombinant erythropoietin. * G-CSF or GM-CSF. * Interferon or interleukin. * Any HIV-1 vaccine. Excluded within 14 days prior to study entry: * Antiretrovirals. * Acute therapy for any opportunistic or other serious infection. * Therapy for malignancy. * Maintenance with ketoconazole, fluconazole, itraconazole, ganciclovir, foscarnet, pyrimethamine, sulfadiazine, clindamycin, azithromycin, isoniazid, rifampin, rifabutin, ethambutol, pyrazinamide, clofazimine, or clarithromycin. * Prophylaxis for Mycobacterial infection or fungal infections other than Candidiasis. Excluded within 7 days prior to study entry: * Allopurinol. * Omeprazole. * Astemizole. * Terfenadine. * Loratadine. * Psychotropics. * Phenylbutazone. * Barbiturates. * Benzodiazepines. * Monoamine oxidase inhibitors. * H-2 blockers. * Anticonvulsants. * Coumadin anticoagulants. * Oral contraceptives. * Antiarrhythmics. * Diltiazem. * Metronidazole. * Erythromycin. * Chloramphenicol. * Fluoroquinolones. * Disulfiram. Risk Behavior: Excluded: * History of substance or alcohol abuse. * Ingestion of more than 50 g alcohol daily within 6 months prior to study entry. * Recovered alcoholic.