A 52-year-old man with a history of NSAID-induced gastric ulcer requires continued naproxen for osteoarthritis. He is prescribed misoprostol for ulcer prophylaxis. Which property of misoprostol makes it contraindicated in women of childbearing potential?

• A It crosses the placenta and causes fetal renal agenesis
• B It antagonizes progesterone receptors at the endometrium
• C It inhibits placental aromatase and causes fetal virilization
• D It is a prostaglandin E1 analogue that induces uterine contractions ✓

Explanation

Misoprostol is a synthetic prostaglandin E1 analogue that binds EP1 and EP3 receptors on uterine smooth muscle, increasing myometrial tone and causing contractions. This abortifacient property is why it is contraindicated in pregnancy and why it is used therapeutically for cervical ripening and medical abortion. It does not cross the placenta to cause renal malformations, inhibit aromatase, or block progesterone receptors; those mechanisms belong to other drug classes entirely.

Reference: Katzung Basic and Clinical Pharmacology, 15th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.