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Disparities in Emergency Contraceptive Metabolism Dictate Efficacy

Who can join

Ages 18 to 40 · Women · Healthy volunteers welcome

Inclusion Criteria:

* Generally healthy women
* Aged 18-40
* regular menses (every 21-35 days) experiencing ovulatory cycles proven by a single progesterone level of 3 ng/mL or greater during the luteal phase of the screening cycle.

Exclusion Criteria:

* Pregnant, seeking pregnancy, or breastfeeding
* Known allergy to study medication
* Recent use of hormonal contraception
* Irregular periods (\<21 days or \>35 day cycles)
* Routine use of nonsteroidal anti-inflammatory drugs
* Metabolic disorders
* Smoking
* Any condition that would preclude the provision of informed consent
* Using drugs (within 2 weeks of study enrollment) known to interfere with the metabolism of UPA as well as drugs known to be CYP3A4 inducers, inhibitors, or CYP3A drug substrates

About the study

The purpose of this study is to learn more about why some people are at greater risk for oral emergency contraceptive failure while others are not. The investigators want to learn if genetic differences impact the risk of emergency contraception failure.

What is being tested

• Ulipristal acetate (drug)

Sponsor: Oregon Health and Science University · Participants: 140 · Started: Jan 9, 2023

Contact the study team

• Women's Health Research Unit Department of OB/GYN · Phone: 503-494-3666

Official record on ClinicalTrials.gov — NCT05674513

Locations in the U.S.

From ClinicalTrials.gov, data retrieved Sep 30, 2026. Each study sets its own eligibility; the study team decides who can join.