Effect of efavirenz antitretroviral therapy on levonorgestrel concentrations among levonorgestrel implant users over 3 years of concomitant use

Objectives: The antiretroviral efavirenz decreases serum levonorgestrel (LNG) concentrations among LNG implant users. Our primary objective was to compare LNG concentrations between LNG implant users who were or were not taking efavirenz, for up to 33 months after implant initiation. Our secondary objective was to evaluate the pregnancy rate among LNG implant users on efavirenz.