Ethamsylate is known to reduce capillary fragility. Hence it is not effective for uterine bleeding which is more due to the vasodilator prostaglandins. Antiprostaglandins are used since NSAIDs reduce prostaglandin levels by inhibiting cyclooxygenase and decreasing the ratio of prostacyclin to thromboxane. Prostaglandin E2 synthesis Prostaglandin E binding sites are reduced as well.