Selectivity and minimal androgenicity of norgestimate in monophasic and triphasic oral contraceptives.

Abstract

The contraceptive progestin norgestimate (NGM) has a high affinity for uterine progestin receptors and a lack of affinity for androgen receptors similar to that of natural progesterone. NGM's selectivity results in excellent efficacy, cycle control, and minimal androgenicity when it is combined with ethinyl estradiol (EE). Clinical studies of a monophasic regimen of NGM/EE indicate a positive impact on lipid metabolism, revealing an increase in serum levels of high-density lipoprotein cholesterol with a concomitant and significant decrease in the low-density lipoprotein/high-density lipoprotein cholesterol ratio. Little impact on carbohydrate metabolism was noted. Serum levels of sex hormone binding globulin, an indicator of androgen-estrogen balance, also increased significantly with NGM/EE in accordance with its low androgenic activity. A significant between-regimen difference in SHBG was seen in a comparison study of NGM/EE and LNG/EE triphasic formulations (a mean rise of 68.6% with NGM/EE vs a decrease of 6.1% with LNG/EE). NGM's lack of estrogenicity was evidenced by unchanged prolactin levels and absence of effect on the coagulation system. In a large study of the monophasic formulation in 59,701 women, some improvement in acne was reported as well as minimal weight gain. An overview of clinical data is provided from United States and European trials as well as some preclinical data relevant to NGM's selectivity.