Description

Ulipristal acetate is a synthetic steroid derivative of 19-norprogesterone. It is a selective progesterone receptor modulator (SPRM) with both antagonistic and partial agonistic effects on the progesterone receptor. This means it can either block or mimic the effects of progesterone in different tissues.

Indication

Ulipristal acetate is primarily indicated for two main uses:

1. Emergency Contraception: It is used to prevent pregnancy after unprotected sexual intercourse or a known or suspected contraceptive failure. It is effective for up to 120 hours (5 days) after the event.
2. Uterine Fibroids: In a different formulation, it is used for the pre-operative treatment of moderate to severe symptoms of uterine fibroids in adult women of reproductive age.

Mechanism of Action

The mechanism of action of ulipristal acetate depends on its use:

• For Emergency Contraception: Its primary mechanism is the inhibition or delay of ovulation. By binding to progesterone receptors, it prevents or postpones the release of an egg from the ovary, even when the luteinizing hormone (LH) surge has already begun. This makes it more effective than other emergency contraceptives in some cases. It may also alter the endometrial lining, making it less receptive to a fertilized egg.
• For Uterine Fibroids: It acts as an antagonist on the progesterone receptors in the uterine fibroid tissue. This inhibits cell proliferation and induces programmed cell death (apoptosis) in the fibroid cells, leading to a reduction in their size and volume.