Alternative Dosing Strategy for Anti-HIV Drugs

While optimism for the benefits of antiretroviral therapy remain justified, the response to therapy varies widely. This variability arises because of differences among patients in virologic, immunologic, behavioral, and pharmacologic factors, all of which impact therapeutic success.

Antiretroviral agents are presently administered to adults in standard fixed doses. However, the same dose does not produce the same systemic and intracellular concentrations in all patients. Recent research has shown that adjusting the doses of antiretroviral agents to achieve target concentrations in plasma is associated with an improved anti-HIV response compared with standard dose therapy. This study will extend the paradigm of concentration-controlled therapy to develop intensified pharmacologic regimens for patients experiencing persistent viremia while receiving antiretroviral therapy.

Two approaches will be investigated: 1) a regimen that targets concentrations of each antiretroviral drug between the 50th and 75th percentile of expected concentrations in adults; and 2) a novel regimen in which the target concentrations are based upon a desired ratio between phenotypic drug susceptibility (IC90) and the concentrations of pharmacologically active moieties, specifically intracellular nucleoside triphosphates and unbound protease and nonnucleoside inhibitors.

Participants will be randomized to either one of the investigational approaches (Cohort II) or to a control group receiving standard dose therapy (Cohort I). There are two study visits in the first month; after the first month, study visits are scheduled monthly for five additional months. Study visits include laboratory tests of virologic and immunologic parameters, pharmacokinetic sampling, and adherence counseling and monitoring.