Evaluating Pharmacokinetic Interactions With Vaginal Ring Contraceptives and ART

This was a 28 day study from study entry through the final clinic visit. Post-entry visits were scheduled at Days 7, 14, 21 and 28. The Nuvaring was put in place at study entry and removed on day 21. A single pharmacokinetic (PK) blood sample was collected for assay of etonogestrel (ENG) and ethinyl estradiol (EE) at entry (day 0, prior to NuvaRing placement), and on days 7, 14, and 21 after placement of the NuvaRing. For participants on the ARV arms, intensive, 8-hour PK sampling, for assay of efavirenz (EFV) and atazanavir/ritonavir (ATV/RTV) respectively, was performed at study entry (day 0, prior to NuvaRing placement) and 21 days later. ARV sampling was performed at pre-dose (hour 0), and 1, 3, 4, 5, and 8 hours post-dose. Safety was assessed at each study visit.