Quantifying Drug Adherence and Drug Exposure to Antiretroviral Therapy

Overview

The purpose of this study is to evaluate cumulative exposure to tenofovir diphosphate (TFV-DP) using dried blood spots (DBS) in treated HIV-infected patients who are receiving a TFV-based regimen. Using DBS will allow the investigators to assess this simple method to measure drug exposure in the clinical setting. The investigators hypothesize that TFV-DP levels will be lowest in individuals with a detectable viral load and highest in those with viral suppression.

Antiretroviral drug exposure is directly linked to individual host factors which include age, weight, diet, and genetics. However, the main factor impacting long-term drug exposure is drug adherence. Adherence is a strong predictor of HIV treatment outcomes, but measuring adherence is difficult due to the inaccuracy of self-reporting and other commonly used monitoring methods. To date, no gold standard measure to monitor antiretroviral exposure and adherence has been applied in clinical practice. Tenofovir (TFV) and its active metabolite, tenofovir diphosphate (TFV-DP), have distinctive pharmacological characteristics that make them ideal candidates for drug adherence and exposure monitoring. The long half life (\~14-17 days) of TFV-DP in red blood cells (RBC) are properties well suited for monitoring average dose exposure over time. Based on these, the investigators propose that RBC levels of TFV-DP are an accurate and precise measure of long-term drug exposure in HIV-infected individuals. In addition, the investigators aim to quantify TFV-DP in dried blood spots (DBS) as a simple method to measure drug exposure. This is an observational, 48-week prospective study of HIV-infected individuals treated with TFV in which the investigators will compare DBS TFV-DP levels in virologically suppressed vs. non-suppressed individuals and evaluate the utility of TFV-DP in DBS to predict virologic failure and also drug toxicity. To accomplish this, the investigators will approach HIV-infected patients currently taking TFV (which is being prescribed by a primary care physician) and who present to the clinic for regular HIV care. After informed consent is obtained, the investigators will collect extra blood samples for DBS TFV-DP and obtain information on drug adherence. The investigators will also collect extra blood samples for DBS TFV-DP at each subject's subsequent visit for approximately 3 visits in a 48 week period of time.

Conditions

Eligibility

Locations (1)

Outcomes