Impact of Menstrual Cycle on Antiretroviral Pharmacokinetics in Healthy Women

Data suggest that women taking drugs to treat human immunodeficiency virus (HIV) have higher amounts of drugs in their body compared with men taking the same dose of anti-HIV drugs. The reason for this higher drug exposure has not been determined. The primary purpose of this study is to examine whether the pharmacokinetics (factors that determine the amount of drug in the body) of anti-HIV drugs change during different phases of the menstrual cycle in women and ultimately result in higher amounts of drug in the body compared with men. In other words, we plan to examine whether changes in sex hormones throughout the menstrual cycle affect the amount of anti-HIV drugs in women. The antiretroviral drugs atazanavir, ritonavir, tenofovir and emtricitabine will be studied. This study will be conducted in healthy women since HIV may change the pharmacokinetics of anti-HIV drugs.