A preterm neonate at 30 weeks gestation has a haemodynamically significant patent ductus arteriosus with bounding peripheral pulses and a wide pulse pressure. The pharmacological basis for using intravenous indomethacin to close the ductus is:
- A Inhibition of prostaglandin E synthesis, which maintains ductal patency in the fetal circulation ✓
- B Stimulation of alpha adrenergic receptors causing ductal vasoconstriction
- C Blockade of nitric oxide mediated ductal smooth muscle relaxation
- D Direct spasmogenic action of indomethacin on ductal smooth muscle
Correct answer: A. Inhibition of prostaglandin E synthesis, which maintains ductal patency in the fetal circulation
Explanation
Patency of the ductus arteriosus in utero is maintained by prostaglandin E1 and prostacyclin produced locally. At birth, rising oxygen tension suppresses PGE production and the duct closes. Indomethacin, a non-selective COX inhibitor, blocks residual PGE synthesis and allows functional closure. Ibuprofen is an alternative with less effect on renal blood flow. Alpha stimulation and NO blockade are not involved, and indomethacin has no direct spasmogenic action on the ductus.
Reference: Katzung Basic and Clinical Pharmacology, 15th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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