EC PK in Women With Normal and Obese BMI

Eligible women will present to the division research office, at which time a history and physical exam will be completed. Each participant's BMI will be confirmed and she will be assigned to one of two BMI groups (18.5-24.9 versus 30-39.9). At the conclusion of the enrollment visit, the research coordinator will randomize each woman to receive a single-dose pill of either levonorgestrel 1.5mg (like Plan B One-Step® or its generic formulations) or ulipristal acetate 30mg (ellaOne®) on two separate occasions.

Inclusion criteria

• Women aged 18-45 years
• English-speaking
• BMI 18.5-24.9 kg/m2 or obese BMI 30.0-39.9 kg/m2
• Regular menstrual cycles
• No use of medroxyprogesterone acetate at least 6 months prior to study enrollment, unless resumption of two menstrual cycles
• No use of levonorgestrel intrauterine system (levonorgestrel-IUS), etonogestrel implant or combined hormonal contraception at least one month prior to the study and resumption of one menstrual cycle
• Women who are postpartum or post-abortion will be included if they have had at least one menstrual cycle since their last pregnancy

Exclusion criteria

• Prior allergic reaction to LNG-EC or UPA-EC
• Use of hormonal emergency contraception within the past month
• Women who are currently pregnant or who are currently breastfeeding
• History of cancer other than non-melanoma skin cancer
• Medical or surgical conditions or conditions requiring therapies known to impact sex steroid production or metabolism

• Use of HAART therapy for management of HIV infection
• Concomitant use of CYP3A4 inducers like rifampin, barbiturates, carbamazepine, lamotrigine, bosentan, felbamate, griseofulvin, oxcarbazepine, phenytoin, St. John's Wort and topiramate
• Current participation in any other trial of an investigational medicine or device in the three months leading up to this study