INCREASED METABOLIC-CLEARANCE OF ACETAMINOPHEN WITH ORAL-CONTRACEPTIVE USE

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  • 1 January 1982
    • journal article
    • research article
    • Vol. 60  (3) , 338-341
Abstract
The effect of chronic low-dose oral contraceptive steroid use on the pharmacokinetics of i.v. acetaminophen [an analgesic] was determined. Eight women using low-dose (< 50 .mu.g) estrogen oral contraceptive steroid for > 3 mo. were matched for age and weight (mean age, 25.9 yr; mean wt, 58.3 kg) with 8 female controls not using the steroid (mean age, 26.0 yr; mean wt, 55.5 kg). No subject was taking other drugs. Oral contraceptive steroid subjects had a lower elimination half-life of acetaminophen (2.12 h) than controls (2.71 h) (P < 0.005). Volume of distribution was similar for both groups (oral contraceptive group, 1.04 l/kg; controls, 0.96 l/kg; NS [not significant]). Total metabolic clearance was significantly higher in oral contraceptive subjects (5.81 per vs. 4.12 ml/min per kg for controls; P < 0.02). As volume of distribution and body weight are similar for both groups, the decrease in acetaminophen elimination half-life among contraceptive steroid users is the result of increased total metabolic clearance. Low-dose estrogen oral contraceptive steroid may stimulate the metabolism of a conjugatively metabolized drug such as acetaminophen, in contrast to contraceptive steroid impairment of the clearance of some oxidatively metabolized drugs, with antipyrine being the prototype.