a Regimens of both 21 and 28 days are listed as the same formulation.
b Based on estimates of approximate progestin potencies (reviewed by Dorflinger, 1985).
c Also contains the inactive enantiomer dextronorgestrel.
formulations in that the total steroid dose can be reduced without compromising effectiveness in preventing pregnancy or cycle control. It should be noted, however, that the triphasic formulations containing norethindrone are actually slightly higher in total hormone dose than the two lowest-dose monophasic formulations that contain the same two hormones (Ovcon 35, and Brevicon/Modicon/ Genora 0.5/35; Table C-1 and Table C-3).
Over the next five years, a number of new oral contraceptive formulations are likely to become available in the American market. Several of these (e.g., Cilest, Marvelon, and Femodene; see Table C-4) are already marketed in a number of countries worldwide, including many European countries. Cilest, which will be marketed as OrthoCyclen in the United States, was recently approved by the FDA. These products are all low-estrogen formulations—30 or 35 μg of ethinyl estradiol. They contain new 19-nortestosterone progestins, which are