Which of the following is the most important reason methylergometrine is avoided in the active management of the third stage in a woman with severe preeclampsia?
- A It causes sustained contraction of smooth muscle and can precipitate a hypertensive crisis ✓
- B It antagonizes the action of magnesium sulfate
- C It crosses the placenta and causes fetal bradycardia
- D It increases the risk of uterine rupture in the third stage
Correct answer: A. It causes sustained contraction of smooth muscle and can precipitate a hypertensive crisis
Explanation
Ergot alkaloids produce prolonged tonic contraction of vascular smooth muscle through alpha adrenergic agonist activity, causing vasoconstriction and a sharp rise in blood pressure. They are therefore contraindicated in hypertensive disorders of pregnancy. Oxytocin, which lacks this vascular effect, is the preferred prophylactic uterotonic in preeclampsia. Ergometrine acts only after placental separation, so fetal effects are irrelevant, and it does not interact with magnesium sulfate.
Reference: Dutta's Textbook of Obstetrics, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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