The effect of OCS on the disposition and elimination of caffeine was examined. Caffeine (250 mg) was administered orally to 13 healthy males, nine healthy females taking no OCS, and nine healthy females on OCS. The t1/2 (beta) was significantly prolonged in women on OCS (10.7 +/- 3.0 hr vs. 6.2 +/- 1.6) (p less than 0.001) as compared to women taking no OCS. Women on OCS had a significantly lower total plasma clearance (0.79 +/- 0.21 ml/min/kg vs. 1.3 +/- 0.35) and free clearance (1.12 +/- 0.28 ml/min/kg vs. 1.97 +/- 0.57) that women not taking OCS. Volumes of distribution and plasma binding were similar in both groups of females. When women taking no OCS were compared with men, all pharmacokinetic parameters were similar except for volume of distribution, which was significantly larger in the women (p less than 0.05). We conclude that OCS impair the elimination of caffeine.
PIP: The disposition and elimination of caffeine were measured in 13 healthy males, 9 healthy females taking no oral contraceptives (OCs), and 9 healthy women taking OCs to determine the effect of OCs on caffeine clearance. All subjects received 250 mg of caffeine, and the elimination half-life was determined. In women taking OCs, the half-life was prolonged significantly (P .001) compared to non-OC-using women (approximately 10.7 hours vs. 6.2, respectively). Similarly, women on OCs had significantly lower total plasma clearance (.79 ml/minute/kg vs. 1.3) and free clearance (1.12 ml/minute/kg vs. 1.97) than nonOC users (women). Both groups of women had similar volumes of distribution and plasma binding. NonOC-using women had the same pharmacokinetic parameter values as men, except for volume of distribution, which was significantly larger in women (P .05). Hence, the authors conclude that OC use impairs caffeine elimination.