A study published last year in the journal Pain found that the effectiveness of narcotic pain killers varied across the menstrual cycle and according to whether a woman was taking oral contraceptives. Researchers investigated pain levels post IV administration of morphine, pentazocine or placebo in two groups of women, normally cycling (n=30) and taking oral contraceptives (n=35) during the follicular and luteal phases of the menstrual cycle. Researchers measured responses to three types of pain: heat, ischemic, and pressure pain sensitivity, both before and after analgesic administration. Change scores were evaluated.
The two groups demonstrated opposite pain responses and differing levels of analgesia. Normally cycling women experienced more heat related pain during the follicular versus the luteal phase, but less ischemic pain. While women using oral contraceptives experienced the exact opposite response: more heat pain during the luteal phase and less ischemic pain during the follicular phase. What was really interesting was that post analgesic administration, normally cycling women experienced less pain during the follicular phase-or a greater analgesic response than women using oral contraceptives. Normally cycling women also experienced more opioid-associated side effects.
This research, though preliminary, demonstrates the need to consider a woman’s hormonal state, (cycle phase and oral contraceptive usage) when addressing pain-related conditions.