Selective progesterone receptor modulator (SPRM)
Partial agonist–antagonist at the progesterone receptor, tissue by tissue
- Agonist or antagonist by tissue
- Delays ovulation → emergency contraception
- Shrinks fibroids
- Endometrial changes are expected from the mixed activity
- Neither pure agonist nor pure blocker: delays LH surge and ovulation at mid-cycle
- ➔ ulipristal acetate (ELLA) — emergency contraception to 120 h, ahead of levonorgestrel's 72
- Mifepristone is the full antagonist cousin at higher receptor occupancy
- ⚠ Hepatotoxicity history belongs to the discontinued fibroid indication (ESMYA, EU), not ELLA single-dose
Drugs with this mechanism (1)
- Ulipristal acetate — Selective progesterone-receptor modulator for emergency contraception.
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