Oral contraceptives



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.

Precautions

No form of birth control (except abstinence from sexual intercourse) is 100 percent effective. However, oral contraceptives can be highly effective when used properly. Teens and young women who anticipate having sexual intercourse should discuss the options with a healthcare professional.

Oral contraceptives do not protect against AIDS or other sexually transmitted diseases . For some protection against such diseases, teenage males and young men need to use a latex condom . Also, oral contraceptives are not effective immediately after a young woman begins taking them. Physicians recommend using other forms of birth control for the first one to three weeks. Then users should follow the instructions of the physician who prescribed the medicine.

Smoking cigarettes while taking oral contraceptives greatly increases the risk of serious side effects. Females who take oral contraceptives should not smoke cigarettes.

Seeing a physician regularly while taking this medicine is very important. The physician will note unwanted side effects, and patients should follow his or her advice on how often they should be seen.

Young women who take oral contraceptives should be sure to tell the healthcare professional in charge before they undergo surgical or dental procedures, laboratory tests, or emergency treatment.

This medicine may increase sensitivity to sunlight. Females using oral contraceptives should avoid too much sun exposure and should not use tanning beds, tanning booths, or sunlamps until they know how the medicine affects them. Some females taking oral contraceptives may get brown splotches on exposed areas of their skin. These usually go away over time after the women stop taking birth control pills.

Oral contraceptives may cause the gums to become tender and swollen or to bleed. Careful brushing and flossing, gum massage, and regular cleaning may help prevent this problem. Users should check with a physician or dentist if gum problems develop.

Side effects

Serious side effects are rare in healthy females who do not smoke cigarettes. In women with certain health problems, however, oral contraceptives may cause problems such as liver cancer , noncancerous liver tumors, blood clots, or stroke . Healthcare professionals can help prospective users weigh the benefits of being protected against unwanted pregnancy against the risks of possible health problems.

The most common minor side effects are nausea , vomiting , abdominal cramping or bloating, breast pain , tenderness or swelling, swollen ankles or feet, tiredness, and acne. These problems usually go away as the body adjusts to the drug and do not need medical attention unless they continue or they interfere with normal activities. Other side effects should be brought to the attention of the physician who prescribed the medicine. Teens and young women should check with the physician as soon as possible if any of the following side effects occur:

  • menstrual changes, such as lighter periods or missed periods, longer periods, or bleeding or spotting between periods
  • headaches
  • vaginal infection, itching , or irritation
  • increased blood pressure

Women who have any of the following symptoms should get emergency help right away. These symptoms may be signs of blood clots:

  • sudden changes in vision, speech, breathing, or coordination
  • severe or sudden headache
  • coughing up blood
  • sudden, severe, or continuing pain in the abdomen or stomach
  • pain in the chest, groin, or leg (especially in the calf)
  • weakness, numbness , or pain in an arm or leg

The adverse effects of oral contraceptives can be impossible to predict. Other than avoiding smoking, there are no effective means of preventing side effects. All observed adverse effects should be reported to a physician promptly.

Oral contraceptives may continue to affect the menstrual cycle for some time after a young woman stops taking them. Women who miss periods for several months after stopping this medicine should check with their physicians. Other rare side effects may occur. Anyone who has unusual symptoms while taking oral contraceptives should get in touch with her physician.

A doctor explains to a teenage girl how to use birth control pills. ( LWA-Stephen Welstead/Corbis.)
A doctor explains to a teenage girl how to use birth control pills.
(© LWA-Stephen Welstead/Corbis.)

Interactions

Oral contraceptives may interact with a number of other medicines. When interaction occurs, the effects of one or both of the drugs may change or the risk of side effects may be greater. Anyone who takes oral contraceptives should let the physician know all other medicines she is taking and should ask whether possible interactions can interfere with drug therapy.

These drugs may make oral contraceptives less effective in preventing pregnancy. Anyone who takes these drugs should use an additional birth control method for the entire cycle in which the medicine is used:

  • ampicillin
  • penicillin V
  • rifampin (Rifadin)
  • tetracyclines
  • griseofulvin (Gris-PEG, Fulvicin)
  • corticosteroids
  • barbiturates
  • carbamazepine (Tegretol)
  • phenytoin (Dilantin)
  • primidone (Mysoline)
  • ritonavir (Norvir)

In addition, taking the following medicines with oral contraceptives may increase the risk of side effects or interfere with the medicine's effects:

  • Theophylline: Effects of this medicine may increase, along with the chance of unwanted side effects.
  • Cyclosporine: Effects of this medicine may increase, along with the chance of unwanted side effects.
  • Troleandomycin (TAO): Chance of liver problems may increase. Effectiveness of oral contraceptive may also decrease, raising the risk of pregnancy.

The list above does not include every drug that may interact with oral contraceptives. Women should be sure to check with a physician or pharmacist before combining oral contraceptives with any other prescription or nonprescription (over-the-counter) medicine. As with any medication, the benefits and risks should be discussed with a physician.

KEY TERMS

Cyst —An abnormal sac or enclosed cavity in the body filled with liquid or partially solid material. Also refers to a protective, walled-off capsule in which an organism lies dormant.

Endometriosis —A condition in which the tissue that normally lines the uterus (endometrium) grows in other areas of the body, causing pain, irregular bleeding, and frequently, infertility.

Fallopian tubes —The pair of narrow tubes leading from a woman's ovaries to the uterus. After an egg is released from the ovary during ovulation, fertilization (the union of sperm and egg) normally occurs in the fallopian tubes.

Fetus —In humans, the developing organism from the end of the eighth week to the moment of birth. Until the end of the eighth week the developing organism is called an embryo.

Fibroid tumor —A non-cancerous tumor of connective tissue made of elongated, threadlike structures, or fibers, which usually grow slowly and are contained within an irregular shape. Fibroids are firm in consistency but may become painful if they start to break down or apply pressure to areas within the body. They frequently occur in the uterus and are generally left alone unless growing rapidly or causing other problems. Surgery is needed to remove fibroids.

Hormone —A chemical messenger secreted by a gland or organ and released into the bloodstream. It travels via the bloodstream to distant cells where it exerts an effect.

Jaundice —A condition in which the skin and whites of the eyes take on a yellowish color due to an increase of bilirubin (a compound produced by the liver) in the blood. Also called icterus.

Migraine —A throbbing headache that usually affects only one side of the head. Nausea, vomiting, increased sensitivity to light, and other symptoms often accompany a migraine.

Mucus —The thick fluid produced by the mucous membranes that line many body cavities and structures. It contains mucin, white blood cells, water, inorganic salts, and shed cells, and it serve to lubricate body parts and to trap particles of dirt or other contaminants.

Ovary —One of the two almond-shaped glands in the female reproductive system responsible for producing eggs and the sex hormones estrogen and progesterone.

Pelvic inflammatory disease (PID) —Any infection of the lower female reproductive tract (vagina and cervix) that spreads to the upper female reproductive tract (uterus, fallopian tubes and ovaries). Symptoms include severe abdominal pain, high fever, and vaginal discharge. PID is the most common and most serious consequence of infection with sexually transmitted diseases in women and is a leading cause of female fertility problems.

Uterus —The female reproductive organ that contains and nourishes a fetus from implantation until birth. Also called the womb.

Parental concerns

Parents become concerned that teens who use oral contraceptives are at risk of becoming sexually active. Although studies have been limited, they have failed to show that availability of oral contraceptives leads to an increase in sexual activity among adolescent girls.

Oral contraceptives do not protect against sexually transmitted diseases. When used for contraception, they should be limited to monogamous relationships.

Although the list of potential side effects and adverse effects is very long and contains some severe risks, the actual frequency of these risks is low. In most cases, oral contraceptives have a very high safety margin.

Resources

BOOKS

Mcevoy, Gerald K., et al. AHFS Drug Information 2004 . Bethesda, MD: American Society of Healthsystems Pharmacists, 2004.

Siberry, George K., and Robert Iannone, eds. The Harriet Lane Handbook , 15th ed. Philadelphia: Mosby, 2000.

PERIODICALS

Kaunitz, Andrew M. "Enhancing oral contraceptive success: The potential of new formulations." American Journal of Obstetrics & Gynecology 190, no. 4, Suppl. (April 2004): S23–S29.

ORGANIZATIONS

American Academy of Dermatology. PO Box 4014, Schaumburg, IL 60168–4014. Web site: http://www.aad.org.

American Board of Obstetrics and Gynecology. 2915 Vine Street, Dallas, TX 75204. Web site: http://www.abog.org.

Planned Parenthood Federation of America. 434 West 33rd St., New York, NY 10001. Web site: http://www.plannedparenthood.org.

WEB SITES

"Update on Oral Contraceptives." American Family Physician. Available online at http://www.aafp.org/afp/991101ap/html (accessed September 28, 2004).

Deanna M. Swartout-Corbeil, R.N. Samuel Uretsky, PharmD



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