Overview
Ulipristal acetate is a selective progesterone receptor modulator used as an emergency contraceptive for prevention of pregnancy following unprotected intercourse or contraceptive failure. It works by delaying or inhibiting ovulation when taken before the luteinizing hormone surge. It is not intended for routine contraceptive use.
Mechanism of Action
Ulipristal acetate is a selective progesterone receptor modulator with antagonistic and partial agonistic effects at the progesterone receptor. It binds to the human progesterone receptor, preventing progesterone from occupying its receptor, which delays follicular rupture and inhibits ovulation when administered before the LH surge.
Indications
- Emergency contraception for prevention of pregnancy following unprotected intercourse
- Emergency contraception following known or suspected contraceptive failure
Common Doses
- 30 mg
Dosage
Single 30 mg tablet taken orally as soon as possible within 120 hours (5 days) after unprotected intercourse or contraceptive failure. Effectiveness decreases with time after unprotected intercourse.
Contraindications
- Known or suspected pregnancy
Side Effects
- Headache
- Nausea
- Abdominal pain
- Dysmenorrhea
- Fatigue
- Dizziness
- Breast tenderness
- Delayed menses
Interactions
- Metabolized primarily by CYP3A4 enzyme
- Strong CYP3A4 inducers (rifampin, carbamazepine, St. John's wort) may reduce effectiveness
- Strong CYP3A4 inhibitors may increase exposure
- May reduce effectiveness of hormonal contraceptives if started within 5 days of administration
Counseling Points
- Take as soon as possible within 120 hours after unprotected sex
- Not for routine birth control
- Does not protect against STIs
- May cause menstrual irregularities
- Use backup contraception if resuming hormonal contraceptives
- Seek medical attention if severe abdominal pain occurs
- Take a pregnancy test if period is delayed by more than 7 days