EC PK in Women With Normal and Obese BMI

Pharmacokinetics of Levonorgestrel and Ulipristal Acetate Emergency Contraception in Women With Normal and Obese Body Mass Index

A well-designed pharmacokinetics (PK) study may identify the physiologic basis for observed differences in levonorgestrel emergency contraception (LNG-EC) and ulipristal acetate emergency contraception (UPA-EC) failure rates in women with normal and obese BMI. The investigators propose a study to compare serum LNG and UPA levels after administration of a single-dose of LNG-EC or UPA-EC. The investigators hypothesize that there will be no difference in PK parameters between women with normal BMI and obese women.

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