"Estrophasic" dosing: A new concept in oral contraceptive therapy.

Abstract

The first of a new "estrophasic" type of oral contraceptive with 20 microg ethinyl estradiol on cycle days 1 through 5, 30 microg ethinyl estradiol on days 6 through 12, and 35 microg ethinyl estradiol on days 13 through 21 and 1 mg norethindrone acetate throughout the cycle (Estrostep; Parke-Davis, Morris Plains, NJ) combines a continuous low progestin dose with a low, gradually increasing estrogen dose. It was developed to ensure good cycle control while conferring the benefits of low hormone content, such as minimizing estrogen-related side effects. In a double-blind, randomized, parallel-group trial, Estrostep provided acceptable cycle control and excellent tolerableness, comparable to that of the 30-microg ethinyl estradiol monophasic control drug. In a second study Estrostep demonstrated a neutral impact on serum lipids, like the triphasic control drug. This new oral contraceptive design offers a useful low-dose alternative to existing combination preparations.