Once-daily antiretroviral therapy is being used to treat adolescents and young adults with HIV-1 infection. When new antiretrovirals (ARVs) are developed, information on kinetics is collected in adults, and then in children, but often the adolescent age group is under-represented in initial or even later pharmacokinetics studies, so specific data on appropriate drug doses to use in adolescents may be lacking; it is assumed that they should receive the adult dose. Furthermore, as newer drugs are used in combination regimens, more information becomes available on drug interactions that might not have been initially anticipated. This information is usually generated in studies of adults, with little or no specific information in children or adolescents. This is an open-label, 24-hour, single-dose pharmacokinetic study.