Estrogen potencies of three new low-dose oral contraceptives.

The estrogen potencies of three new oral contraceptive formulations--Brevicon, Modicon, and Lo/Ovral--were determined. Brevicon and Modicon were found to have estrogen potency equal to mestranol 50 mug and equal to or greater than Norinyl 1 + 50 and Ortho-Novuum 1 + 50. Lo/Ovral, which is identical to Ovral in the type and ratio of progestin but 40 per cent lower in drug content, could be estimated to have an estrogen potency of 0.73 relative to mestranol 50 mug and therefore, by inference, to Brevicon and Modicon.