Alcohol elimination at low blood concentrations among women taking combined oral contraceptives.

Objective: Evidence implicating a role of natural and synthetic estrogens and/or progestin on ethanol pharmacokinetics can be traced back to the mid-1970s when reports of large metabolic differences were found suggesting that sex hormones interfered with the efficient clearance of alcohol at the liver microsomal level. Research teams in this area manipulate sex hormone levels by either examining natural-cycling women at different phases of their menstrual cycle or others taking oral contraceptives that synthetically regulate the hormonal fluctuations. These collective studies (over a dozen to date involving over 200 participants) have all been similar in focus and outcome. With one important exception, the published laboratory research since 1976 has failed to replicate the earliest research suggesting sex hormone effects. One well-controlled study in 1987 did generate renewed interest in the area with the paradoxical finding that progesterone actually enhanced alcohol elimination at low blood concentrations (<.025%). The present study represented the most direct attempt to replicate this particular finding using 5-minute breath alcohol readings that extended below blood alcohol concentrations of .025%.

Method: A total of 17 women taking combined oral contraceptives were tested during both menstruation and the luteal phase (Days 16-22) of their cycle in counterbalanced sequence.

Results: Pharmacokinetics differences were not found.

Conclusion: These results contribute further to a literature base demonstrating the limited effects of both natural and synthetic sex hormones on alcohol metabolism in women.