A Phase 4 interventional study of Ulipristal acetate in Contraceptive Usage, sponsored by Oregon Health and Science University. Recruiting at 1 site in United States. Open to female participants aged 18 Years to 40 Years, including healthy volunteers. Per ClinicalTrials.gov, last updated 2026-07-09.
Sponsored by Oregon Health and Science University · Phase 4, Interventional, and Treatment
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.
Each of us can respond differently to a drug or medication based on our genetics. An emergency contraceptive, ulipristal acetate or UPA, normally works by stopping or delaying the ovary from releasing an egg (ovulation). Our bodies break down UPA in order to use it through a system call the cytochrome P450 pathway but this pathway can be faster or slower depending on our genetics. The investigators want to learn more about how our individual genetic differences in this pathway change how the ovary responds to UPA. The overall goal of this research is to improve the effectiveness of emergency contraception for all people.
132 studies on the registry are indexed under Contraception Behavior; 20 are open to participants now.
This study's planned enrollment of 140 is below the median of 382 across 106 interventional studies indexed under Contraception Behavior.
Browse Contraception Behavior studies →Oregon Health and Science University is the lead sponsor of 696 studies on the registry; 131 are open to participants now.
Of its 52 completed or terminated interventional studies of FDA-regulated products, 39 (75%) have results posted.
Counted across the registry records on this site, refreshed daily.
Go through the criteria one by one — yes, no or not sure — and take the list to your doctor or the study team. Kept in this browser only.
Exclusion Criteria:
Underlined terms in the criteria open these too. Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Ways of preventing pregnancy. “Highly effective” methods fail less than 1% of the time a year when used correctly — for example an IUD or an implant.
Criteria usually say which methods count and how long to keep using them after the last dose, sometimes for male participants too. Some studies accept a partner’s vasectomy if it was confirmed successful and that person is the participant’s only sexual partner.
Before you join, the study team explains what taking part involves — its purpose, what happens, the risks and possible benefits — and answers your questions, so you can decide freely. Consent is usually recorded on a form (the informed consent form, ICF) signed by you or, where the law allows, by someone legally authorised to decide for you.
You can keep asking questions during the study, you are told of new information that matters, and you can choose to leave at any time.
CYP3A is a group of enzymes, mainly CYP3A4, in the liver and gut that break down many medicines. Some medicines, supplements and foods (grapefruit, St John’s wort) slow them down or speed them up, which changes how much of a study drug stays in the body.
Studies list them so they can be avoided or switched; bring a list of everything you take, including supplements.
Contraception
Ways of preventing pregnancy. “Highly effective” methods fail less than 1% of the time a year when used correctly — for example an IUD or an implant.
Criteria usually say which methods count and how long to keep using them after the last dose, sometimes for male participants too. Some studies accept a partner’s vasectomy if it was confirmed successful and that person is the participant’s only sexual partner.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Informed consent
Before you join, the study team explains what taking part involves — its purpose, what happens, the risks and possible benefits — and answers your questions, so you can decide freely. Consent is usually recorded on a form (the informed consent form, ICF) signed by you or, where the law allows, by someone legally authorised to decide for you.
You can keep asking questions during the study, you are told of new information that matters, and you can choose to leave at any time.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
CYP3A (CYP3A4) inhibitors and inducers
CYP3A is a group of enzymes, mainly CYP3A4, in the liver and gut that break down many medicines. Some medicines, supplements and foods (grapefruit, St John’s wort) slow them down or speed them up, which changes how much of a study drug stays in the body.
Studies list them so they can be avoided or switched; bring a list of everything you take, including supplements.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Ulipristal acetate 30mg orally x 1 dose with pharmacokinetic and pharmacodynamics testing in individuals with active CYP3A5 alleles
Drug: Ulipristal acetate
Ulipristal acetate 30mg orally x 1 dose with pharmacokinetic and pharmacodynamics testing in individuals without active CYP3A5 alleles
Drug: Ulipristal acetate
Evaluating the pharmacodynamic and pharmacokinetic outcomes after 1 dose of Ulipristal acetate 30mg in individuals with and without active CYP3A5 alleles
Delay in follicular rupture
Follicular rupture (yes/no) by ultrasound. Defined as the disappearance of or \>50% reduction in size of the leading follicle
Time frame: over 1 menstrual cycle (assessed up to approximately 30 days)
Concentration of UPA
mean concentration maximum (Cmax) for UPA
Time frame: 5 days after taking study drug
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Studies of the drug tested here: Ulipristal acetate
Oregon Health and Science University →