Objectives: To compare the effects of a combined oral contraceptive (COC) taken continuously with those of one of similar composition taken cyclically on 30 variables related to haemostasis, lipids, carbohydrates, bone metabolism, and sex hormone-binding globulin (SHBG).
Methods: Randomised, open-label, multicentre, comparative substudy of a larger phase 3 trial involving 147 healthy women (age 18-49 years). Participants received the COC either continuously (levonorgestrel [LNG] 90 μg/ethinylestradiol [EE] 20 μg) or cyclically (21/7 days pattern; LNG 100 μg/EE 20 μg).
Results: After 13 pill packs, changes in total cholesterol (+0.23 vs. -0.06 mmol/l), low-density lipoprotein cholesterol (+0.25 vs. -0.12 mmol/l), and high-density lipoprotein cholesterol(3) (-0.06 vs. -0.15 mmol/l) differed significantly (p<0.05) between the continuous and cyclic regimens, respectively. Increases were significantly greater (p <0.05) for protein C antigen (+11.8% vs. +6.1%) and SHBG (+791 vs. +565 nmol/l), and significantly smaller (p <0.05, ranks) for D-dimer (+19 vs. +37 μg FE/l).
Conclusions: Overall, the continuous and cyclic regimens affected metabolic variables similarly. The larger increase in SHBG with the continuous COC is consistent with a higher net oestrogenic effect due to a lower daily dose of LNG. Prospective studies are required to determine the long-term effects of this continuous COC regimen.