One year study of effects of an oestrogen-dominant oral contraceptive on serum high-density lipoprotein cholesterol, apolipoproteins A-I and A-II and hepatic microsomal function.

The effects over 1 year of an oestrogen-dominant oral contraceptive containing ethinylestradiol and levonorgestrel on serum high-density lipoprotein cholesterol, apolipoproteins A-I and A-II and liver microsomal enzyme activity assessed by antipyrine kinetics, were investigated in 21 healthy, young women. HDL cholesterol and apolipoprotein concentrations rose and hepatic microsomal enzyme activity fell during the first month of the treatment, and remained affected throughout the year. After discontinuation of treatment, the lipid and apolipoprotein concentrations and the microsomal enzyme activity returned to their pretreatment levels within 1 month. The drug, by reducing hepatic enzyme activity, may have influenced both the antipyrine elimination rate and the high-density lipoprotein concentration.