A 1-year randomized study to evaluate the effects of a dose reduction in oral contraceptives on lipids and carbohydrate metabolism: 20 microg ethinyl estradiol combined with 100 microg levonorgestrel.

OBJECTIVES: To evaluate the impact on lipid and carbohydrate variables of a combined one-third ethinyl estradiol (EE)/levonorgestrel (LNG) dose reduction in oral contraceptives.

METHODS: In an open-label, randomized study, a dose-reduced oral contraceptive containing 20 microg EE and 100 microg LNG (20 EE/100 LNG) was compared with a reference preparation containing 30 microg EE and 150 microg LNG (30 EE/150 LNG). One-year data from 48 volunteers were obtained.

RESULTS: We found a decrease of HDL2 cholesterol and increases of low-density lipoprotein cholesterol, very low-density lipoprotein cholesterol and total triglycerides in both treatment groups from baseline to the 13th treatment cycle. Although for four of six variables, the changes in the 20 EE group were lower compared with the 30 EE group, none of the differences between the two treatments were statistically significant. The median values for the fasting levels of insulin, C-peptide and free fatty acids slightly increased or remained unchanged while the fasting glucose levels slightly decreased after 13 treatment cycles. While the glucose area under the curve (AUC) (0-3 h) was similar in both groups during the OGTT, the insulin AUC(0-3 h) was less increased in the 20 EE/100 LNG group compared with the 30 EE/150 LNG group. None of the differences between the treatment groups for any of the carbohydrate metabolism variables were statistically significant at any time point. Both study treatments were safe and well tolerated by the volunteers.

CONCLUSION: Similar effects on the lipid and carbohydrate profiles were found for both preparations. The balanced one-third EE dose reduction in this new oral contraceptive caused slightly lower, but insignificant, changes in the lipid and carbohydrate variables compared with the reference treatment.