Effect of norethisterone and levonorgestrel in low-dose multiphasic oral contraceptives on serum lipids.

In a parallel, multicenter study in Norway and Finland involving a total of 196 healthy women (mean age 22.4 years, range 18-30), the effects on serum lipids and lipoproteins of two multiphasic oral contraceptives containing ethinyl estradiol (EE) but different progestins were examined. One formulation contained EE 35 micrograms and norethisterone (NET) 0.5 mg on days 1-7 and days 17-21 and elevated NET 1.0 mg during the midphase (days 8-16). The other formulation contained EE 30 micrograms on days 1-6 and days 12-21 and 40 micrograms on days 7-11 and phased levonorgestrel (LGN): 50 micrograms (days 1-6), 75 micrograms (days 7-11) and 125 micrograms (days 12-21). Both formulations induced significant elevation of total cholesterol (6.7 and 4.1%), Apo B (8.1 and 7.0%) as well as HDL (6.4 and 3.7%) for the EE/NET and EE/LGN formulation respectively. Mean serum levels of triglycerides were significantly elevated (58 and 47%). However, all mean serum lipid and lipoprotein values remained within the normal range, and no change in the calculated cholesterol ratio (HDL/total cholesterol) nor lipoprotein ratio (HDL/(HDL+LDL)) was observed. No significant difference between the formulations could be detected with respect to the effect on serum lipids and lipoproteins measured. The change in total cholesterol was smaller than reported in many studies of monophasic preparations. Taken together, these data suggest that only small alterations in lipid metabolism are elicited by these oral contraceptives.