Tri-Norinyl (Norethindrone / Ethinyl Estradiol / Norethindrone / Ethinyl Estradiol) - Clinical Pharmacology

CLINICAL PHARMACOLOGY

Combination oral contraceptives act by suppression of gonadotrophins. Although the primary mechanism of this action is inhibition of ovulation, other alterations include changes in the cervical mucus (which increase the difficulty of sperm entry into the uterus) and the endometrium (which may reduce the likelihood of implantation).