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The Facts on Oral Contraception

Monica Holmberg, PharmD
Published Online: Wednesday, June 1, 2005   [ Request Print ]

Preventing pregnancy is as old as history itself. Four thousand years ago, women inserted plugs of acacia gum or crocodile dung in the vagina to create an environment that was unfriendly to sperm. Thus they prevented conception and avoided unwanted pregnancy.

Oral contraception had begun by the fourth century BC. The extract of the siphium plant was so effective and was used so much that the plant became extinct. Other plants used included Queen Anne's lace, wild carrot, ivy, juniper, willow, pine, and cabbage.

There was, however, a delicate balance between preventing pregnancy and causing harm to the woman. The use of toxic agents such as lead, arsenic, mercury, and strychnine in the Middle Ages often led to death. Fortunately, today's medicine offers a wide range of oral contraceptives (OCs) that are both safe and effective.

Oral Contraceptive Formulations

OCs were initially introduced in the 1960s. Today they take many forms. OCs can be divided into 2 major categories: progestin- only pills and combination pills, which contain both progestin and estrogen. Progestin prevents ovulation (the discharge of an egg from an ovary). Progestin also creates an environment in the uterus that helps to keep the egg from implanting. In addition, it thickens mucus secretions in the cervix so that the sperm cannot move as freely.

Progestin-Only Pills

Progestin-only "minipills"are taken daily for continuous treatment. They must be taken every day because they work primarily through changes in the endometrium in the uterus and changes in the cervix. If patients take a pill 3 or more hours later than scheduled, they should use an additional means of contraception for 48 hours.

Progestin-only pills typically are used by women who are breast-feeding, are unable to take estrogen, or are over 40 years old. Irregular menstrual bleeding is a common side effect. The progestin-only pill is 90.4% to 98.9% effective in preventing pregnancy.

Combination Pills

Although estrogen is not essential for contraception, it stabilizes the endometrium to minimize breakthrough bleeding. It also increases the activity of progestin.

Combination OCs involve daily treatment for 21 days, followed by 7 treatment-free days. During that time, menstruation usually occurs. Both 21-day and 28-day regimens are on the market. In both products, the first 21 pills are hormone-containing pills or "active"pills. The additional 7 tablets for days 22 to 28 are placebos that do not contain hormone. These inactive "reminder"pills can help make women remember to take a pill every day.

Some combination OCs contain a fixed dose of estrogen and progestin throughout the 21 days. Other formulations gradually increase the estrogen or progestin doses over 21 days. Increasing the hormone dose throughout the cycle copies the way the body naturally releases hormone. These regimens also reduce the total hormone dose and may help to minimize side effects.

When used as directed, combination OCs may be 99.9% effective at preventing pregnancy. In actual use by average women, however, they are about 97% to 98% effective.

More Information on Oral Contraceptives

Beginning an OC can be overwhelming. See Tables 1 and 2 for some important information. You also can ask your pharmacist or your doctor.

Aside from contraception, using OCs may decrease the risk of cancer of the ovaries and the uterus. They also help women who have painful menstruation or problems with their period. Using OCs, however, is not without risk. Patients using OCs have a greater chance of having a stroke or a heart attack, especially if they smoke or have high blood pressure. During the first year of OC therapy, they have a 3 to 4 times greater risk of clotting in the legs or in the lungs.

Women who have had clotting or a stroke or certain kinds of tumors should not take OCs. Women with active liver disease, abnormal uterine bleeding, or high triglycerides also should not take these drugs. Women who are pregnant or who are over 35 years old and smoke more than 15 cigarettes a day should not use them. OCs should be used with caution in women if they have high blood pressure that is poorly controlled, if they have migraine headaches, or if they take medications to prevent seizures.

The most common side effects are nausea and breast tenderness. Weight gain has not been shown to be a side effect.

Contraception has come a long way since the days when women used plant extracts and vaginal plugs. Oral contraception today is both safe and effective. The large number of products available offers a reasonable means for a wide range of patients to prevent pregnancy.

Dr. Holmberg is a pharmacist with Phoenix Children's Hospital, Phoenix, Ariz.





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