Effects of an oral contraceptive on hepatic size and antipyrine metabolism in premenopausal women.

Liver volume and antipyrine disposition have been investigated in healthy premenopausal women who received 30 microgram ethinyl oestradiol + 500 microgram dl-norgesterol as an oral contraceptive. Six months' treatment was associated with a 17% increase in liver volume while no change occurred in age-matched control subjects. In the same subjects the contraceptive decreased antipyrine clearance by 21%. Thus the contraceptive markedly reduced drug-metabolizing activity per unit volume of liver by 33%. In additional subjects, discontinuation of the contraceptive resulted in a 30% increase in antipyrine clearance. These observations confirm that conventional oral contraceptive therapy to premenopausal women increases hepatic size and that it is a potent inhibitor of drug-metabolizing activity.