Indomethacin inhibits the synthesis and release of prostaglandins from myometrial cells by selectively inhibiting the cyclo-oxygenase 1 enzyme. By this action, the synthesis of prostaglandins from arachidonic acid is inhibited. So, indomethacin prevents the stimulation of the uterus by oxytocin / prostaglandin agonists
What is true about indomethacin? It can...
Extra info: In combination with methotrexate, indomethacin can increase methotrexate's toxicity. Indomethacin should not be used during early pregnancy since it can cause malformations and spontaneous abortion.
Regarding uterine tocolytics: I. NSAIDs should be stopped after 36 weeks gestation. II. COX-2 inhibitors are significantly more potent than indomethacin.
Extra info: NSAIDs should be stopped before 32 weeks as use after this gestation period increases the risks of premature closure of the ductus arteriosus. Indomethacin is a potent inhibitor of COX-1 and COX-2 enzymes and it is unclear at present how the newer selective COX-2 inhibitors will comparewith indomethacin as tocolytics. Selective COX-2 inhibitors should have a much better safety profile, however.