Do aspirin and acetaminophen affect total menstrual loss?

Two commonly taken over-the-counter analgesics, aspirin and acetaminophen, were compared for: effect on total menstrual loss, effect on total days of menstruation, and effect in reduction of pain due to headaches and/or menstrual cramps. Drugs were administered during a 4-month study according to a double-blind format. During the first 2 months, subjects ingested no drugs whatsoever during their menstrual periods. During the second 2 months, subjects ingested aspirin, acetaminophen, or placebo at the rate of two 325-mg tablets every 4 h to total 8 tablets per day during the first 3 days of their menstrual periods. Statistical analysis of the first 2 periods compared to the last 2 showed no differences in total menstrual weights. The number of days of menstruation in the placebo group was significantly lower (p = 0.0137) than in its own control or in the other groups. Neither analgesic showed a significant reduction in pain due to headache or cramps, although acetaminophen appeared to be slightly more effective than aspirin in reducing menstrual cramps.