Vitex, a medicinal plant also known as monk's pepper or chasteberry, offers several purported medicinal benefits for women coping with infertility, hormonal disturbances, PMS and breast conditions. Although generally safe and associated with few side effects, chasteberry is not appropriate for women using hormonal contraceptives.
Birth Control Function
Hormone-based birth control involves the use of estrogen and/or progesterone, two female reproductive hormones. According to MayoClinic.com, the hormones in contraceptives act by preventing the ripening and release of fertile eggs. Birth control also makes the womb inhospitable to sperm and fertilized eggs. Examples of hormone-based contraceptives include the Ortho Evra patch, Nuvaring, Depo-Provera shot, Mirena IUD, and several brands of contraceptive pills. Copper IUDs, condoms, diaphragms and spermicides do not contain, or depend upon, synthetic hormones.
Vitex and Hormones
Vitex directly alters levels of the hormones involved in fertility, conception and pregnancy. According to the Sloan-Kettering Cancer Center, vitex can influence not only progesterone and estrogen, but also luteinizing hormone and follicle-stimulating hormone -- which are responsible for ovulation and fertility. Vitex also contains chemical precursors to prolactin and testosterone. In theory, vitex's hormonal content could either augment or degrade the efficacy of hormonal contraceptives.
Hormonal contraceptives often cause unpleasant side effects due to their influence on female reproductive hormones. Elevated levels of estrogen and progesterone can cause headaches, nausea, breast tenderness and changes in menstruation. Because vitex can also increase the production of estrogen and progesterone, it could cause a greater incidence and severity of contraceptive-related side effects. Sloan-Kettering specifically advises people taking hormonal contraceptives to avoid vitex supplements.
Vitex may reduce the effectiveness of contraceptives, according to the National Center for Complementary and Alternative Medicine. Historically, herbalists have recommended vitex to enhance fertility in women desiring pregnancy. According to Sloan-Kettering, vitex can act as a precursor to the hormones involved in ovulation. This may negate the ovulation-inhibiting effects of birth control. As a result, women using chasteberry alongside birth control could experience an increased risk of unplanned pregnancy.