Adefovir Dipivoxil to Treat Hepatitis B in HIV-Infected Patients

This study will evaluate the safety and effectiveness of adding the experimental drug adefovir dipivoxil to lamivudine for treating hepatitis B virus (HBV) infection in HIV-infected patients with liver cirrhosis. Adefovir inhibits HBV by interfering with replication of the virus's genetic material. In some people, the drug has been active against strains of HBV that are resistant to lamivudine; it may also have some activity against HIV. HIV-infected patients 21 years of age and older with chronic hepatitis B infection and liver cirrhosis who have received lamivudine treatment for at least 1 year may be eligible for this 48-week study. Candidates will be screened with a complete medical history, blood tests and a 24-hour urine collection. Blood tests include HLA typing (a test of genetic markers on white blood cells that permit specialized immunology studies). Within 4 weeks, candidates who appear eligible for the study will have a physical examination and medical history, an abdominal ultrasound (imaging test using sound waves) to check for cancer of the liver, chest X-ray and electrocardiogram (EKG). Blood and urine tests will also be done, and women who can become pregnant will have a pregnancy test. Patients who meet the study criteria and decide to participate will then start treatment with one 10-mg adefovir pill per day by mouth. In addition, patients will continue to take all other medications prescribed by their doctor. Follow-up clinic visits will be scheduled as follows: * Days 1, 3, 5, 7, 10 and 21 - Blood will be drawn for specialized immunology tests and to measure blood levels of HIV and HBV. * Weeks 2, 4, 8, 12, 16, 20, 24, 28, 32, 36, 40, 44 - Blood and urine (single sample) tests will be done to determine the side effects of adefovir and its effect on the HBV infection. * Week 48 or early termination (end of study) - Blood tests (including tests for hepatitis C and D), abdominal ultrasound and a 24-hour urine collection to evaluate kidney functi