Hair It Is: The Long and Short of Monitoring Antiretroviral Treatment

Potent combination antiretroviral therapies have favorably altered the natural history of HIV infection in the United States. Suboptimal drug concentrations are major predictors of treatment failure and the emergence of viral mutations that confer resistance. Nonadherence seems the most common reason for suboptimal drug levels (1). The ability of patients to adhere to antiretroviral regimens may be influenced by regimen complexity, recreational drug use, depression, lack of education, cost considerations, unstable living situations, side effects, and personal beliefs about the safety and efficacy of the drugs (1, 2). Drug level may also be influenced by coadministration of medications and nontraditional treatments that induce the metabolism or efflux pumping of antiretroviral drugs (3). In addition, the bioavailability of some antiretroviral agents is marginal and can be further reduced by gastrointestinal conditions, which are common in patients with AIDS.

Many methods have been evaluated for determining adherence to antiretroviral therapies, including self-report, pill counting, tracking cap-opening events, and measuring drug concentrations in blood and urine (4). These techniques tend to assess behavior over short periods (even self-report, which can be provided for long periods, is considered accurate for only the short term). Use of medication organizer containers and different sources of medication can interfere with pill-counting and cap-opening adherence measures. Measurement of drug levels in plasma is the most sensitive indicator of treatment adequacy; however, plasma levels reflect only the medication doses administered within 1 to 2 days of sampling, and they have limited predictive value for long-term treatment outcomes (5). The ideal measure of medication exposure would be objective, would assess drug levels …