What are birth control pills and how do they work?
Oral contraceptives or birth control pills contain synthetic female hormones. They work largely by preventing the release of an egg from an ovary, or ovulation. If no egg is released, there can be no pregnancy.
Stopping ovulation is not the only way birth control pills can work. The progestin or synthetic progesterone in birth control pills also changes the physical and chemical environment of the female reproductive tract, making it hostile for sperm.
What are the different types of birth control pills?
The active ingredients in birth control pills are synthetic versions of the female hormones estrogen and progesterone. Combination oral contraceptives are birth control pills that contain both ingredients. There are some birth control pills that are progesterone-only pills. Sometimes referred to as "minipills," progestin-only pills are especially useful for women who cannot take estrogens. They are also suitable for women who are breastfeeding because they don't interfere with the production of milk.
The various brands of combination birth control pills generally come packaged in blister packs containing 21 or 28 tablets. After finishing the 21 day pack, there is a week without any pills when withdrawal bleeding occurs. This will be like a regular menstrual period but generally lighter. Then a new pack is started on the same day of the week as the start of the previous pack.
In the 28-day pack, typically 21 pills are active pills containing hormones and the other pills are "reminder" pills without hormones. Some reminder pills may contain iron. By taking reminder pills, a woman takes a pill each day, which can help maintain her birth control regimen. The progestin-only pills come in 28-day packs with all the pills being active containing hormone. With pills containing continuous hormone, there isn't any scheduled time of bleeding, but spotting or unexpected bleeding may occur.
It is possible to reduce the number of menstrual periods a woman has in a year or even to eliminate them all together. Since 2003, brands of birth control pills have been available in 84-day regimens for what's known as extended-cycle oral contraception. Women who use this method take an active pill every day for 12 weeks. Then they may stop or take a placebo for seven days, during which time they will have their period. Or they may continue to take an active pill for up to a year. Some brands of birth control pills sold for extended-cycle oral contraception conclude the regimen with seven active pills that contain a smaller dose of estrogen, which can have the effect of reducing the amount of bleeding that occurs during a period.
Are there differences among birth control pills?
Birth control pills can differ not only in the number of active ingredients, but also in the way ingredients are dosed:
Monophasic birth control pills contain the same amount of ingredient in each active pill.
Multiphasic birth control pills contain varying levels of hormones through the month. They were designed to minimize side effects such as breakthrough bleeding, which is bleeding that occurs between menstrual periods.
Low-dose oral contraceptives contain less estrogen than other types of birth control pills. They contain 20 micrograms of estrogen, compared to 30 to 50 in other birth control pills.
What are the side effects/health risks of birth control pills?
In healthy women, oral contraceptives have few side effects. Nausea, breast tenderness, weight gain, changes in mood, and breakthrough bleeding are the most common ones -- and these usually diminish with continued use. Pregnancy is still possible. With proper use, though, that possibility is minimized. Oral contraceptives do not protect against HIV or other sexually transmitted infections.
The following symptoms may indicate serious -- even life-threatening -- side effects:
- Pain in the chest or abdomen
- Severe headache
- Blurry vision
- Pain and/or swelling in the legs or thighs
A woman who develops any of those symptoms should seek immediate medical attention.
Though oral contraceptives are usually well-tolerated in healthy women, there can be serious complications associated with their use. Some of the serious conditions include:
Central Nervous System
- Benign and cancerous tumors of the liver
- Blood clot in the blood vessels that support the intestines
- Gallbladder disease
For women with previous health issues, birth control pills may be a poor choice for contraception. The biggest concern is the generation of blood clots, strokes, and heart attacks -- especially in women who are older and who smoke. In fact, women who smoke and take birth control pills dramatically increase their risk of developing strokes and heart attacks. The risk increases with age and amount of cigarette use. Birth control pills that contain estrogen may worsen diabetes.
Women who experience migraine headaches, particularly those over age 35 and those who experience migraines with visual symptoms, are also at increased risk of stroke when using oral contraceptives.
There is some evidence that long-term use of birth control pills may increase the risk for cervical cancer. And while studies show a slightly higher risk for breast cancer in women who have used the pill, no conclusions have been reached. Oral contraception may increase liver cancer risk.
Oral contraceptives have been shown in studies to reduce the risk of ovarian and endometrial cancers.
What are the drug interactions of birth control pills?
The following drugs may reduce the effectiveness of oral contraceptives:
- Chloramphenicol (Chloroptic, Chloramphenicol Sodium Succinate)
- Erythromycin (Benzamycin, Emgel, Ilotycin)
- Rifampin (Rifadin)
- Sulfa drugs
Anticonvulsants (seizure medications)
- Carbamazepine (Tegretol, Carbatrol, Equetro)
- Lamotrigine (Lamictal, Lamictal XR)
- Phenytoin (Dilantin, Dilantin 125, Dilantin Infatabs)
- Topiramate (Topamax)
Drugs that may increase blood levels of oral contraceptives include:
- Acetaminophen (Tylenol)
- Ascorbic acid (Vitamin C)
- Atorvastatin (Lipitor)
- Fluconazole (Diflucan)
- Itraconazole (Sporanox, Sporanox Injection, Sporanox Oral Solution)
How well do birth control pills work to prevent pregnancy?
Used properly, birth control pills work exceedingly well. With both combination pills and progesterone only pills, the pregnancy rate is less than 1%. Even among women who don't use the pills properly – that is, who don't take them each day as directed – the pregnancy rate is about 8%. Using birth control pills properly is particularly important with the progestin-only minipills. To be most effective, they must be taken at the same time every day.
What are some examples of birth control pills?
Combination Oral Contraceptives
Monophasic (all active pills contain the same level of hormones)
- Desogestrel and Ethinyl Estradiol Tablets (Apri)
- Norethindrone-Ethin Estradiol (Balziva-28)
- Norethindrone-Ethin Estradiol (Brevicon-28)
- Progestin/Estrogen (Cryselle-28)
- Ethinyl Estradiol and Ehtynodiol Diacetate (Demulen 1/35)
- Ethinyl Estradiol and Ethynodiol Diacetate (Demulen 1/50)
- Desogestrel and Ethinyl Estradiol (Desogen)
- Norethindrone and Ethinyl Estradiol (Femcon Fe)
- Ethyinyl Estradiol and Norethindrone (Geneora 1/35)
- Mestranol and Norethindrone (Genora 1/50)
- Gilders Fe
- Norethindrone/Ethinyl Estradiol (Junel)
- Norethindrone Acetate and Ethinyl Estradiol (Junel Fe)
- Desogestrel and Ethinyl Estradiol and Ethinyl Estradiol (Kariva)
- Ethinyl Estradiol Ethynodiol (Kelnor)
- Levonorgestrel (Levlen)
- Levonorgestrel and Ethinyl Estradiol (Levora 21)
- Levonorgestrel/Ethinyl Estradiol (Levora 28)
- Norgestrel and Ethinyl Estradiol (Lo Ovral 28)
- Norethindrone Acetate (Loestrin 1.5/30)
- Ethinyl Estradiol and Norethindrone (Loestrin 24 Fe)
- Norethindrone Acetate and Ethinyl Estradiol (Loestrin Fe 1.5/30)
- Ethinyl Estradiol and Norgestrel (Low-Ogestrel)
- Norethindrone Estradiol (Microgestin 1.5/30)
- Norethindrone/Ethynyl Estradiol and Fumarate (Microgestin Fe 1/20)
- Ethinyl Estradiol-Norethindrone (Modicon)
- Ethinyl Estradiol-Norgestimate (Mononessa)
- Norethindrone/Ethinyl Estradiol (Necon 0.5/35)
- Norethindrone/Ethinyl Estradiol (Necon 1/35)
- Mestranol and Norethindrone (Necon 1/50)
- Ethinyl Estradiol and Levonorgestrel (Nordette 28)
- Ethinyl Estradiol and Norethindrone (Norinyl 1/35)
- Mestranol and Norethindrone (Norinyl 1/50)
- Ethinyl Estradiol and Norethindrone (Nortrel 0.5/35)
- Ethinyl Etradiol/Norethindrone (Nortrel 1/35)
- Drospirenone and Ethinyl Estradiol (Ocella)
- Ethinyl Estradiol and Norgestrel (Ogestrel)
- Ethinyl Estradil and Desogestel (Ortho-Cept)
- Ethinyl Estradiol and Norgestimate (Ortho-Cyclen)
- Ethinyl Estradiol and Norethindrone (Ortho-Novum 1/35)
- Mestranol and Norethindrone (Ortho-Novum 1/50)
- Ethinyl Estradiol and Norethindrone (Ovcon 35)
- Ethinyl Estradiol/Norethindrone (Ovcon 50)
- Norgestrel and Ethinyl Estradiol (Ovral 28)
- Ethinyl Estradiol and Levonorgestrel (Portia)
- Ethinyl Estradiol Norgestimate (Previfem)
- Ethinyl Estradiol and Desogestrel (Reclipsen)
- Ethinyl Estradiol and Desogestrel (Solia)
- Ethinyl Estradiol and Norgestimate (Sprintec)
- Ethinyl Estradiol/Drospirenone (Yasmin 28)
- Ethinyl Estradiol and Norethindrone (ZenChent)
- Ethinyl Estradiol Ethynodiol Diacetate (Zovia 1/35)
- Ethinyl Estradiol Ethynodiol Diacetate (Zovia 1/50)
Multiphasic (dose of hormone changes over the course of 21 days)
- Ethinyl Estradiol and Norethindrone (Aranelle)
- Desogestrel/Ethinyl Estradiol (Caziant)
- Ethinyl Estradiol and Desogestrel (Cesia)
- Ethinyl Estradiol and Desogestrel (Cyclessa)
- Ethinyl Estradiol and Levonorgestrel (Enpresse)
- Ethinyl Estradiol and Norethindrone (Estrostep)
- Ethinyl Estradiol and Norethindrone (Jenest - 28)
- Ethinyl Estradiol and Norethindrone (Leena 28)
- Ethinyl Estradiol and Norethindrone (Necon 10/11)
- Ethinyl Estradiol and Norethindrone (Necon 7/7/7)
- Ethinyl Estradiol and Norethindrone (Nortrel 7/7/7)
- Ethinyl Estradiol and Norethindrone (Ortho Tri Cyclen)
- Ethinyl Estradiol and Norethindrone (Ortho-Novum 7/7/7)
- Ethinyl Estradiol and Norethindrone (Tilia Fe)
- Ethinyl Estradiol and Norethindrone Acetate (Tri Legest Fe)
- Levon and Ethinyl Estradiol (Tri-Levlen)
- Ethinyl Estradiol and Norethindrone (Tri-Norinyl)
- Ethinyl Estradiol and Norethindrone (Tri Previfem)
- Ethinyl Estradiol and Norethindrone (Tri-Sprintec)
- Ethinyl Estradiol and Norethindrone (TriNessa)
- Ethinyl Estradiol and Levonorgestrel (Triphasil)
- Ethinyl Estradiol and Levonorgestrel (Trivora)
- Ethinyl Estradiol and Desogestrel (Velivet)
Combination Oral Contraceptives (Low Estrogen)
- Ethinyl Estradiol and Levonorgestrel (Alesse-28)
- Ethinyl Estradiol/Desogestrel (Aviane)
- Ethinyl Estradiol/Desogestrel (Azurette)
- Norethindron Acetate and Ethinyl Estradiol (Gildess Fe 1/20)
- Ethinyl Estradiol/Norethindrone (Junel 1/20)
- Ethinyl Estradiol/Norethindrone (Junel Fe 1/20)
- Ethinyl Estradiol and Desogestrel (Kariva)
- Ethinyl Estradiol and Levonorgestrel (Lessina)
- Ethinyl Estradiol/Norethindrone (Loestrin 1/20)
- Ethinyl Estradiol/Norethindrone (Loestrin Fe 1/20)
- Ethinyl Estradiol and Levonrgestrel (Lutera-28)
- Ethinyl Estradiol/Norethindrone (Microgestin 1/20)
- Ethinyl Estradiol/Norethindrone (Microgestin Fe 1/20)
- Ethinyl Estradiol, Desogestrel (Mircette)
- Ethinyl Estradiol and Levonorgestrel (Sronyx)
- Ethinyl Estradiol and Drospirenone (YAZ-28)
Progestin-Only Oral Contraceptives
- Norethindrone (Micronor)
- Norethindrone (Camila)
- Norethindrone (Errin)
- Norethindrone Acetate (Jolivette)
- Norethindrone (Nor-QD)
- Norethindrone (Nora-BE)
- Ortho Micornor (Ortho Micronor)
- Norgestrel (Ovrette)
Extended Cycle Oral Contraceptives (combination)
- Levonorgestrel, Ethinyl Estradiol (LoSeasonique)
- Levonorgestrel, Ethinyl Estradiol (Quasense)
- Levonorgestrel, Ethinyl Estradiol (Seasonale)
- Levonorgestrel, Ethinyl Estradiol (Seasonique)
- Levonorgestrel, Ethinyl Estradiol (Jolessa)
- Levonorgestrel, Ethinyl Estradiol (Lybrel)
Ther Clin Risk Management v,4(5); Oct 2008: Evaluation of extended and continuous use oral contraceptives
www.kaiserpermanente.org (Drug Encyclopedia)
www.cancer.gov "Oral contraceptives and Cancer Risk: Questions and Answers" http://www.cancer.gov/cancertopics/factsheet/Risk/oral-contraceptives
American College of Obstetricians and Gynecologists: "Birth Control Pills"
Women's Health Resources
Wayne Blocker, MD
Board Certified Obstetrics and Gynecology