Interactions between ethanol and oral contraceptive steroids.

We investigated the effect of oral contraceptive steroids (OCSs) on plasma ethanol disposition and tolerance to ethanol. Fifty-four healthy women between 18 and 40 years old were classified as light (31) or moderate (23) drinkers. Each group was further subdivided into controls (no OCS; 10 light, seven moderate drinkers), 30 or 35 micrograms estrogen OCS (14 light, 11 moderate drinkers), and 50 micrograms estrogen OCS (seven light, five moderate drinkers). Four of the subjects were studied on a second occasion, thus acting as their own controls with and without OCS use. All women were studied between days 14 and 21 of their pill/menstrual cycle. Plasma ethanol concentrations and two simple tests of motor function were measured for 6 hours after ethanol, 0.9 gm/kg in orange juice drank over a 30-minute period. The groups were well matched for age and weight. There were no significant differences between any of the six subgroups in mean peak plasma ethanol concentration, mean time to peak, mean AUC, or mean rate of ethanol disappearance. This was also the case for the four women who acted as their own controls. Analyses between those receiving high and low progestogen OCSs and between smokers and nonsmokers showed no significant differences. There was acute deterioration in functional performance as measured by two motor function tests in all subjects, regardless of OCS use. Moderate drinkers were significantly less functionally impaired than light drinkers whether with or without OCS use, indicating acquired tolerance. The mean degree of impairment and mean recovery time for both tests were significantly less in the OCS groups than in the control groups. The same trend was seen in the four women who were their own controls. Our results suggest that OCS use may induce some form of "tolerance" to ethanol. However, because there is no evidence of any change in ethanol disposition even at high plasma ethanol concentrations (greater than 100 mg/dl), women taking OCSs should not attempt to drink more than usual.