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
and blocks spontaneous contractions. In case of very early delivery (before 30 weeks), indomethacin can be given as suppository. Indomethacin can cause GI complaints and dizziness with the mother. The foetus, however, can suffer from serious adverse effects i.e. renal failure. Therefore, indomethacin can only be used for this purpose in low dose and a short period of time. On the other hand, indomethacin can be applied because of its adverse effect: in order to decrease the amount of amniotic fluid in situations of polyhydramnios.
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.