Pharmacological, metabolic and clinical aspects of new oral contraceptive associations containing natural estrogens [Aspetti farmacologici, metabolici e clinici delle nuove associazioni contraccettive a base di estrogeni naturali]

Introduction of new compounds containing natural estrogens represented a major development in the field of hormonal contraception. Micronized estradiol (E2) and its estere valerate (EV), is more easily metabolized by the liver than ethynylestradiol (EE). This causes minimal metabolic impact, but the weak estrogenic activity needs not be antagonized by androgenic progestin and requires progestin capable to stabilize the endometrium. Dienogest (DNG), an antiandrogenic progestin with a short half-life, is associated with estradiol valerate (EV) in a quadriphasic fashion. In comparison to EE/levonorgestrel (LNG), EV/DNG is more neutral on metabolism and coagulation. Furthermore, it does not seem to negatively affect the cardiovascular system and breast. Cycle control is optimal with a higher prevalence of amenorrhea and reduction of menstrual flow. For this reason EV/DNG can be tehrapeutic for heavy menstrual bleedings. Nomegestrol acetate (NOMAc), an anti-andogen progestin with a long half-life is combined in monophasic regimen with micronized E2. E2/NOMAc is more neutral than EE/LNG on metabolism and more neutral than EE/DRSP on coagulation. NOMAc reduces peripheral tissue estrogen formation, and this may be beneficial for the breast. The two formulations exert a high contraceptive efficacy similar to the ones containing EE, but with less estrogen-related side-effects. The additional benefits due to DNG and NOMAc need to be further explored.