Indomethacin is administered to a preterm neonate to close a haemodynamically significant patent ductus arteriosus. The mechanism by which it closes the ductus is:

• A Direct smooth muscle contraction of the ductal wall independent of prostaglandins
• B Stimulation of bradykinin release, which constricts the ductus arteriosus
• C Inhibition of prostaglandin E synthesis, removing the vasodilator that keeps the ductus open ✓
• D Blockade of nitric oxide synthase in ductal endothelium

Explanation

Patency of the fetal ductus arteriosus is maintained by circulating prostaglandin E (and prostacyclin), which relaxes ductal smooth muscle. After birth, the fall in PGE levels allows closure. Indomethacin, a non-selective COX inhibitor, suppresses PGE synthesis and promotes constriction and closure. This same physiology explains why prostaglandin E1 infusion is used to keep the ductus open in duct-dependent congenital heart disease.

Reference: Katzung's Basic and Clinical Pharmacology, 16th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.