Combined oral contraceptives show clear differences in effect on the tissue factor-initiated coagulation test of activated protein C resistance, which is dependent on the presence and dosage of levonorgestrel. Multiphasic levonorgestrol oral contraceptives differ from monophasic contraceptives and resemble third-generation contraceptives.
PIP: The significance of levonorgestrel dose in oral contraceptives for effects on coagulation is presented. A study in Germany was conducted to test the activated protein C resistance and assess the differences induced by various combined oral contraceptives (COCs). A resistance to activated protein C of monophasic COCs with desogestrel, gestodene, or norgestimate close to the value of women heterozygous for factor V Leiden was confirmed. Higher concentrations of levonorgestrel counteract the increase in resistance. Thus, monophasic and multiphasic COCs with levonogestrel were distinguished according to their effects on tissue-factor-initiated resistance to activated protein C. A more detailed comparison of in-vitro coagulation effects and epidemiology will further assess the plausibility and mechanisms of resistance in relation to activated protein C acquired by COC use and venous thromboembolism.