Blood Levels of Abacavir in HIV Infected Adolescents

ABC is approved for the treatment of HIV in adults and children, but it is unclear if currently recommended ABC doses are appropriate for adolescents. Previous data suggest ABC clearance in children is about twice that found in adults, but limited data exist on the pharmacokinetics of ABC in adolescents. This study will evaluate the 8-hour pharmacokinetics of ABC in HIV infected adolescents who are currently on ABC-containing treatment regimens. There will be two groups in this study. Group 1 participants will be 13 to 17 years old. Group 2 participants will be 18 to 25 years old. All participants will receive a 300 mg dose of ABC as either a single-agent tablet or a combination tablet of ABC, lamivudine, and zidovudine (whichever they are currently taking). Participants will have a medical history assessment and a physical exam at screening and study entry. Participants will also be asked about adherence to their ABC-containing regimen at study entry. During the 8-hour drug level study, blood collection for pharmacokinetic analysis will occur prior to taking ABC, and at 0.5, 1, 2, 3, 4, 6, and 8 hours after taking ABC.