Antipyrine elimination in saliva after low-dose combined or progestogen-only oral contraceptive steroids

A 'low-dose' combined oral contraceptive steroid (OCS) preparation containing 30 µg ethinyloestradiol and 150 µg levonorgestrel was found to reduce significantly antipyrine clearance in a group of women acting as their own controls. An OCS preparation containing only a progestogen (75 µg norgestrel) did not reduce antipyrine clearance in a second group of women. The evidence suggesting that the oestrogen component of combined OCS preparations could be responsible for the reduction in antipyrine clearance is discussed.