Efficacy and Safety of Switching From Retrovir to Tenofovir or Abacavir in HIV-infected Patients

Inclusion Criteria: * HIV-infection with undetectable viral load * Antiretroviral treatment including Retrovir for more than three months * If fertile female: Negative pregnancy test and use of safe contraception * Negative HBs-antigen titer Exclusion Criteria: * Prior treatment with abacavir or tenofovir * Resistance towards abacavir or tenofovir * Tissue type HLA-B5701 * Renal disease * Diabetes Mellitus * Osteoporosis * Pregnant or lactating subjects * Intravenous drug abuse * Hypersensitivity towards drugs or active ingredient used * ALAT \> 5 times upper normal level * Current alcohol or substance abuse judged by the Investigator to potentially interfere with subject compliance