Oral-Contraceptive Steroids Impair the Elimination of Theophylline

The influence of OCS and sex differences on the disposition of theophylline has been studied in 12 healthy young men (29 ± 4 years old), 13 healthy young women (29 ± 12), and 10 healthy young women (24 ± 3) receiving OCS for a period greater than 6 months. The elimination t 1 2 was longer in women taking oral contraceptives (523 ± 110 min) than in women not on oral contraceptives (386 ± 157). Weight-normalized plasma clearance of theophylline was less in women taking oral contraceptive steroids (0.70 ± 0.15 ml · min · kg) than in women not on oral contraceptive steroids (0.98 ± 0.32). Plasma binding and volume of distribution were not different between the two groups of women. Weight-normalized clearance, weight-normalized volume of distribution, plasma t 1 2, and plasma binding were not different between men and women not taking OCS.