Inclusion Criteria

Patients may be eligible for this study if they:

• Are HIV-positive.
• Are at least 16 years old (consent of parent or guardian required if under 18).
• Are taking a stable Videx-containing anti-HIV regimen, using Videx tablets either once or twice a day, for at least 2 weeks prior to the screening visit.
• Score 2 or higher on the GSRS questionnaire for 1 or more of the following symptoms at the first 2 study visits: abdominal pain, nausea and vomiting, borborygmus, abdominal distension, and loose stools.
• Agree to use an effective barrier method of birth control during the study.
• Are available for at least 8 weeks.

Exclusion Criteria

Patients will not be eligible for this study if they:

• Are pregnant or breast-feeding.
• Are taking Videx in liquid form, nelfinavir, or amprenavir.
• Have a history of pancreatitis or gallstones.
• Abuse alcohol or require drugs which, in the opinion of the investigator, may increase the risk of pancreatitis.
• Have had treatment for an active opportunistic (AIDS-related) infection within 4 weeks of the screening visit. Patients with chronic candidiasis (yeast infection) or bacterial infection will be allowed.
• Are receiving or plan to receive chemotherapy for cancer.
• Plan to change their medications within 8 weeks following the screening visit.
• Are receiving investigational drugs or are participating in a clinical trial involving anti-HIV medications. Patients in Phase IV studies (studies that evaluate the long-term safety and effectiveness of a drug, usually after the drug has been approved by the FDA) may be eligible.
• Have an active, ongoing gastrointestinal disease or infection such as colitis, diverticulitis, Crohn's disease, peptic ulcer disease, giardiasis, or cryptosporidiosis.
• Are unable to take medications by mouth.
• Have severe diarrhea.
• Have peripheral neuropathy (a condition affecting the nervous system) or other condition or prior therapy that, in the opinion of the investigator, would affect the study.