Ulipristal acetate (UPA) is used as emergency contraception and for uterine fibroids. Its receptor-level mechanism is:

• A Oestrogen receptor agonist that accelerates LH surge, causing early ovulation before fertilisation can occur
• B Selective progesterone receptor modulator (SPRM) that inhibits or delays ovulation and alters endometrial receptivity ✓
• C Pure progesterone receptor antagonist that blocks implantation by completely opposing progesterone at the endometrium
• D GnRH receptor antagonist that suppresses LH and FSH, preventing follicular development

Explanation

Ulipristal acetate is a selective progesterone receptor modulator (SPRM) with mixed agonist/antagonist properties depending on tissue. For emergency contraception, its primary action is inhibition or delay of ovulation (even close to the LH surge), more effective than levonorgestrel in this time window. For fibroid treatment, it suppresses fibroid growth through endometrial/myometrial progesterone receptor modulation and indirect pituitary effects. It differs from mifepristone (a pure progesterone antagonist with anti-glucocorticoid activity).

Reference: KD Tripathi, Essentials of Medical Pharmacology, 8th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.