Biphasic has a 21-day pill pack featuring two different amounts of hormone combinations throughout the three-week cycle, and triphasic has a 21-day pill pack with three different hormone dosage amounts throughout the three-week cycle.
The goal of the biphasic and triphasic formulations is to achieve adequate control of the menstrual cycle while using lower doses of both estrogens and progestins, thereby reducing the risk of adverse effects.
Biphasic oral contraceptives use a constant amount of estrogen during the full cycle, but the amount of progestin is lower during the first half of the cycle and increases in the second half.
Many women and many physicians prefer monophasic pills because hormone levels remain consistent, but biphasic and triphasic oral contraceptives are equally effective.
There are three main types of pill packs and hormone combinations – monophasic, biphasic, and triphasic.