What are the types of combined oral contraceptive pills (OCP)?
There are several combined OCP preparations available in Canada. They may be monophasic (each tablet contains a fixed amount of estrogen and progestin), biphasic (each tablet contains a fixed amount of estrogen while the amount of progestin increases in the second half of the cycle) or triphasic preparations (the amount of estrogen may be fixed or variable while the amount of progestin differs in three phases). Biphasic and triphasic formulations eliminate the natural menstrual cycle but attempt to replace it with cyclical variations in steroid dose. These formulations were initially developed with the intent of lowering the total steroid content of combined OCPs while decreasing side effects such as mid cycle bleeding, but newer monophasic preparations also have low total steroid doses and excellent tolerability.
