D4T or Abacavir Plus Vitamin Enhancement in HIV-Infected Patients (DAVE)

Inclusion Criteria: * Be HIV-positive * Be 18 years of age or older * Have a viral load equal to or below 50 copies/mL * Have been on a d4T-containing multiple drug regimen (at least three agents in total) for at least six months * Have been on a stable ARV regimen for the three months prior to enrollment * Have a venous lactic acid measurement above 2.1 mmol/L within the three months prior to enrollment and two consecutive measurements above 2.1 but lower than 6.0 within a two-week period of screening * Be willing to discontinue L-carnitine and/or coenzyme Q10 * Be willing and able to provide informed consent Exclusion Criteria: * Pregnancy or breastfeeding * Venous lactic acid equal to or above 6.0 mmol/L * Previous exposure to abacavir * Virologic rebound while on a previous regimen consisting of dual or triple nucleoside reverse transcriptase inhibitors (NRTIs) * Use of hydroxyurea within the three months prior to enrollment * Use of metformin * Any acute cardiopulmonary illness or infection * New AIDS-defining illness diagnosed within four weeks of enrollment * Riboflavin or thiamine supplementation above 20 mg/day within 30 days prior to enrollment