Studies in menorrhagia: (a) mefenamic acid, (b) endometrial prostaglandin concentrations.

Twenty-two women with unexplained heavy menstrual blood loss (average loss for two cycles of >80 ml) were treated with the prostaglandin synthetase inhibitor menfenamic acid during two consecutive menstruations. There was a significant reduction in menstrual blood loss on mefenamic acid therapy, the median loss being 137 ml before treatment and 76 ml while on treatment. Reduction in menstrual loss was achieved in 20 of the 22 patients but varied from a 2% to 78% reduction. The greater the menstrual loss before treatment, the more it was reduced on mefenamic acid therapy. Endometrial concentrations of prostaglandins E2 and F2 alpha in the follicular phase of the cycle were similar whether or not patients had menorrhagia. In the luteal phase, however, 6 of 14 patients with menorrhagia had higher endometrial prostaglandin E2 and F2 alpha concentrations than all 13 controls.