The effects of mefenamic acid and norethisterone on measured menstrual blood loss

Although there are numerous medical treatments for menorrhagia, in many instances neither the precise diagnosis nor the response to therapy have been assessed objectively. Menorrhagia (menstrual blood loss more than 80 mL per cycle) was diagnosed objectively in 32 (44%) of 72 women with a subjective complaint of heavy menses. All of the 32 women had ovulatory cycles. After random allocation to treatment with either mefenamic acid (500 mg three times daily during menses, N = 17) or norethisterone (5 mg twice daily on days 19-26 of the cycle, N = 15) for two additional cycles, the median menstrual blood loss was reduced from 123 mL (range 86-237) to 81 mL (22-193) (P less than .001) and from 109 mL (81-236) to 92 mL (43-189) (P less than .002) with mefenamic acid and norethisterone, respectively. Apart from a decrease in the median number of days of bleeding, from 7 (5-8) to 5 (3-8) in those women treated with mefenamic acid, no other differences were seen between the groups. We conclude that mefenamic acid and norethisterone were similarly effective in reducing the degree of menstrual blood loss in women with proved menorrhagia, but that 52 and 67% of the women, respectively, remained menorrhagic after 2 months of treatment.