Ulipristal Acetate: Effects in Emergency Contraception
Ulipristal acetate (brand names ellaOne for emergency contraception, Esmya for uterine myomas) is a selective progesterone receptor modulator (SPRM) with two clearly distinct areas of indication. As a single 30 mg dose, ulipristal acetate has been approved in Germany since 2009 for emergency contraception up to 120 hours after unprotected sexual intercourse and is available in pharmacies without a prescription. As a 5 mg daily dose, ulipristal acetate was approved for the treatment of uterine myomas, but its use has been severely restricted since 2020 due to rare severe liver complications.
Compared to levonorgestrel as emergency contraception (morning-after pill), ulipristal acetate works longer and also after the LH surge has begun. Therefore, this substance is the drug of choice when unprotected intercourse occurred during mid-cycle or more than 72 hours ago. Application is simple, safe and effective provided the indication is correct.
Mechanism of Action
Ulipristal acetate selectively binds to the progesterone receptor and acts both agonistically and antagonistically, depending on the tissue. In the pituitary and ovary, ulipristal acetate delays or prevents ovulation by suppressing the preovulatory LH surge. Even after the LH surge has begun, ovulation can be delayed by approximately five days, so that sperm are no longer viable in the female genital tract.
In the endometrium, ulipristal acetate has an antiproliferative effect and reduces implantation capacity. This secondary effect contributes to contraceptive safety, but is not the primary mechanism. In uterine myomas, low-dose continuous use reduces the size of fibroids because progesterone as a growth-promoting factor is blocked.
Pharmacokinetically, ulipristal acetate shows rapid oral bioavailability, with maximum effect occurring 1 to 2 hours after administration. The half-life is approximately 32 hours. Metabolism occurs predominantly hepatically via CYP3A4. Potent CYP3A4 inhibitors and inducers significantly influence levels.
Areas of Application
- Emergency contraception up to 120 hours (5 days) after unprotected intercourse or contraceptive failure
- Uterine myomas with preoperative tumor reduction, in the EU only under strict conditions and after failure of other therapies since 2020
- Research and specialized indications in hormone-sensitive diseases, decided individually
Ulipristal acetate is not suitable for regular contraception. Repeated use in one cycle reduces effectiveness. In pregnancy, ulipristal acetate is contraindicated, so a pregnancy test is advisable if there is suspicion before use.
Dosage and Administration
Emergency contraception: single dose of 30 mg orally, as soon as possible after unprotected intercourse. Effectiveness decreases with increasing latency but is demonstrable up to 120 hours.
Uterine myomas: 5 mg daily for up to three months, individual assessment of indication only in specialized centers with regular liver monitoring, as rare but severe liver complications have occurred.
Administration: tablet taken whole with water. If vomiting occurs within three hours of administration, a repeat dose is required because absorption is not yet complete.
Contraceptive measures after emergency contraception: until the next period or until resumption of regular contraception, additional measures such as condom use should be employed.
Renal insufficiency: generally no dose adjustment required. Hepatic insufficiency: caution in moderate impairment, not recommended in severe hepatic insufficiency.
Side Effects
Frequent (emergency contraception): headache, nausea, abdominal pain, fatigue, dizziness, breast tenderness, cycle disturbances with early or late period.
Occasional: vomiting, mood swings, skin rash, pruritus.
During long-term therapy (uterine myomas): hot flashes, changes in endometrial thickness, hormonal fluctuations, very rarely severe liver reactions with acute liver failure.
Very rare but relevant: acute liver inflammation with cholestasis and transaminase elevation, in individual cases requiring liver transplantation. This complication has led to restrictions on EU approval for myoma treatment.
With emergency contraception: the single dose is generally very well tolerated. Severe side effects are very rare.
Drug Interactions
- Strong CYP3A4 inducers (rifampicin, carbamazepine, phenytoin, St. John's Wort, some antiretroviral agents): reduce the effectiveness of ulipristal acetate. Consider alternatives such as copper IUD in emergency contraception.
- Strong CYP3A4 inhibitors (itraconazole, ketoconazole, ritonavir, clarithromycin, grapefruit juice): increased levels.
- Hormonal contraceptives: ulipristal acetate has a competitive effect on the progesterone receptor. Hormonal contraception should not be started or resumed until five days after ulipristal acetate, as otherwise the effectiveness of both substances is reduced.
- Levonorgestrel as emergency contraceptive: no combination because both can influence each other. If levonorgestrel fails, ulipristal acetate as an alternative is not first choice.
- Antacids and acid suppressants: no relevant interactions.
Special Information
Pregnancy: Ulipristal acetate is contraindicated in an existing pregnancy because an antiprogestin effect endangers pregnancy maintenance. Before use with cycle-specific uncertainty, perform pregnancy test. Breastfeeding: Transfer into breast milk, a nursing break of approximately 7 days after administration is recommended. During this time, express and discard milk.
In obesity: with increasing body weight, the effectiveness of emergency contraceptives decreases. With BMI over 30, a copper IUD should alternatively be considered, which represents the most reliable emergency contraception independent of weight and cycle phase.
Before use: check clear indication, cycle history, rule out existing pregnancy. Inform about effectiveness, side effects, behavior after administration, regular contraception for following months.
After use: if period is delayed or absent, perform pregnancy test. If symptoms persist, heavy bleeding, or suspected pregnancy, seek medical evaluation.
When to see a doctor: with very heavy bleeding, abdominal pain, signs of pregnancy despite emergency contraception, suspected ectopic pregnancy (pain, spotting, dizziness).
Lifestyle: emergency contraception is an acute solution. Reliable regular contraception (oral pill, hormonal IUD, copper IUD, condom) is more effective long-term and also partially protects against sexually transmitted infections.
Ability to drive: if dizziness or pronounced fatigue occurs, assess individually.
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- Raloxifen, SERM in postmenopausal indication
Frequently Asked Questions
How long after unprotected intercourse is ulipristal acetate effective?
Up to 120 hours, that is five days. Effectiveness is highest in the first 24 hours and decreases with increasing latency. With very late administration or in obesity, a copper IUD is the most reliable alternative.
How does ulipristal acetate differ from levonorgestrel as morning-after pill?
Both delay or prevent ovulation. Ulipristal acetate also works after the LH surge has begun and is approved for up to 120 hours. Levonorgestrel is limited to 72 hours and only works as long as the LH surge has not yet begun. At mid-cycle or with long latency, ulipristal acetate is the more effective choice.
Can I start taking the pill again immediately after ulipristal acetate?
Hormonal contraception should not be started or resumed until approximately five days after ulipristal acetate because both substances influence each other at the progesterone receptor. In the meantime, use condoms additionally to ensure reliable contraception.
Is ulipristal acetate less effective in obesity?
Studies show reduced effectiveness with higher body weight and BMI over 30. In obesity, the copper IUD is significantly more reliable as emergency contraception because its effectiveness is independent of weight and cycle phase. Medical or pharmaceutical advice is advisable.
Sources
- EMA, ellaOne (Ulipristal Acetate) EPAR
- Gelbe Liste, Ulipristal Acetate Active Ingredient Profile
- BfArM, Federal Institute for Drugs and Medical Devices
- AWMF, Guidelines for Emergency Contraception and Uterine Myomas
Legal Notice and Disclaimer
The information provided on this page is for general information purposes only and does not constitute medical advice, diagnosis, or treatment recommendation. It does not replace the advice of a licensed physician or pharmacist. For questions about emergency contraception, pharmaceutical or gynecological advice is recommended. All information is based on product information published at the time of creation and recognized scientific sources; the current product information from the manufacturer is always authoritative. Sanoliste assumes no liability for completeness, currency, or accuracy of the information presented. In case of medical emergency, call emergency number 112.