Background:  Antiretroviral (ARV) adherence at the 95% level has been identified as the minimum level of adherence to suppress the majority of individuals to an HIV viral load to < 400 copies/mL. Recent therapies, including non-nucleoside reverse transcriptase inhibitor (NNRTI) regimens, lead to better viral suppression than single protease-inhibitor (PI) therapies in clinical trials. We examined adherence and viral suppression in single-PI and NNRTI-based regimens using 2 validated, objective measures of adherence: unannounced pill counts (UPC) and electronic medication monitoring (EMM).

Methods:  Subjects were recruited from the REACH Cohort and were included if they were on single-PI or NNRTI ARV regimens for at least 3 months prior to study baseline. Adherence was measured by unannounced pill counts in all individuals and electronic medication monitoring in those without mediset pill box organizers. The primary outcome was suppression of HIV viral RNA to < 400 copies/mL. Adherence categories were defined by unannounced pill counts quartiles.

Results:  We followed 110 patients (56 on PI and 54 on NNRTI) for a median of 9.1 months. unannounced pill count data were available on all patients and electronic medication monitoring data were available on 65 patients not using medisets. Viral suppression to < 400 copies was common in individuals on NNRTI-regimens in the highest 3 quartiles of adherence (54 to 100% adherence) whereas viral suppression was only seen in the majority those with greater than 95% adherence to single-PI therapy (see the table below). The odds of virologic suppression were 5.6 times higher for patients on NNRTI regimens than with patients on single-PI regimens when controlling for adherence and other potential confounders (nadir CD4, ARV treatment duration, mono/dual nucleoside exposure) in a multivariable analysis (p = 0.0011). There was no statistically significant difference in adherence by unannounced pill counts in patients receiving NNRTI versus single-PI-containing regimens.

Conclusions:  NNRTI regimens can lead to viral suppression at less than 95% adherence. While NNRTI potency may lead to viral suppression at moderate levels of adherence, near complete adherence improves the probability of durable viral suppression for all regimen types.  

Keywords: adherence ; NNRTI; protease inhibitor