Two oral contraceptives, efficacy, serum proteins, and lipid metabolism: A comparative multicentre study on a triphasic and a fixed dose combination

A triphasic, combined oral contraceptive containing 30 — 40 — 30 μg ethinyloestradiol (EE), and 50 — 75 — 125 μg levonorgestrel was compared with a fixed dose combination containing 30 μg EE and 150 μg desogestrel in a randomized multicentre trial in 193/199 women and 1063/1073 cycles, respectively. The duration of the trial was six months. Eleven centres in Denmark, Sweden, and Norway participated. Contraceptive reliability, bleeding control and side effects were evaluated. Influence on serum sex hormone binding globulin (SHBG) and transcortin was assayed as well as lipid metabolism. Three pregnancies occurred in the group using the triphasic regimen but none in the fixed dose regimen. Two of the three pregnancies were considered drug failures and the third a possible interaction. Possible reasons for the triphasic contraceptive failure are discussed with special reference to a British report on eight pregnancies. Bleeding control appeared to be equally good for the two preparations. However, the number of cycles with spotting, breakthrough bleeding and missed withdrawal bleeding were above the levels reported earlier on the triphasic regimen. About 80 per cent of the women completed the planned six months on either combination. Side effects were generally mild and in accordance with earlier reports on low dose oral contraceptives. Metabolically the triphasic levonorgestrel combination increased SHBG 100 per cent versus 200 per cent for the fixed desogestrel combination. Transcortin rose about 98 and 110 per cent, respectively. Both preparations induced similar changes in the levels of lipids and lipoproteins with the exception of a significant increase in the arachidonic content of cholesterol during treatment with the desogestrel-containing preparation.