Oral Contraceptive Drug Therapies

Definition

Oral contraceptives are medicines taken by mouth to help prevent pregnancy. They are also known as the pill, OCs, or birth control pills.

Description

Oral contraceptives, or birth control pills, contain synthetic forms of two hormones produced naturally in the body. These hormones, estrogen and progestin, regulate the female menstrual cycle. Some types of oral contraceptives use only progestational hormones, but most use a combination of estrogen and progestin. As of 2004, there were three types of oral contraceptives marketed:

• Monophasic use a fixed dose of both estrogen and progestin during the entire cycle.
• 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. This shift in dosage is intended to mimic the natural ovarian cycle.
• Triphasic oral contraceptives may vary both the estrogen and progestin levels at different times during the 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. Reviews of controlled studies have not demonstrated a clear advantage of the newer formulations over the older monophasic drugs.

General use

When taken in the proper amounts, following a specific schedule, oral contraceptives are very effective in preventing pregnancy. Studies show that fewer than one of every 100 females who use oral contraceptives correctly becomes pregnant during the first year of use.

These pills have several effects that help prevent pregnancy. For pregnancy to occur, an egg must become mature inside a woman's ovary, be released, and travel to the fallopian tube. Sperm must travel through the reproductive track to fertilize the egg in the fallopian tube. Then the fertilized egg must travel to the woman's uterus (womb), where it lodges in the uterus lining and develops into a fetus.

The main way that oral contraceptives prevent pregnancy is by keeping an egg from ripening fully. Eggs that do not ripen fully cannot be fertilized. In addition, birth control pills thicken mucus in the woman's body through which the sperm has to swim. Thus it is more difficult for the sperm to reach the egg. Oral contraceptives also change the uterine lining so that a fertilized egg cannot lodge there to develop.

Although contraception is the primary use of these medications, they may also be used to treat adolescent and post-adolescent acne in girls. Some products have this as part of their official indications, but others may be used as well.

Content licensed from:

Author Info: Deanna M. Swartout-Corbeil R.N., Samuel Uretsky PharmD, Thomson Gale, Gale, Detroit, Gale Encyclopedia of Children's Health, 2006

This feature is for informational purposes only and should not be used to replace the care and information received from your healthcare provider. Please consult a healthcare professional with any health concerns you may have.