Structural Biochemistry/Contraceptives

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Contraception, or birth control, is a form of family planning. This method prevents unwanted pregnancies and sometimes also prevents sexually transmitted diseases. Some forms of birth control are meant for only males, and others are meant for women.

Other family planning techniques include abstinence, surgical sterilization, natural family planning, and withdrawal.

Barrier Methods

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Barrier methods of contraception are used as a physical or chemical forms of blockading sperm from having access within the uterus to prevent any fertilization of an egg, and thus, a pregnancy. They have no considerable side effects, except for any allergies to the materials within the devices, and can be used right before sexual intercourse.

Male Condoms: This is the most common form of contraception within the modern world. A male condom is used by a male by rolling the thin tube onto an erect penis before any type of intercourse. It became a very popular contraceptive method in the 20th century and is the most effective form of birth control that prevents most sexually transmitted diseases if only used once. The earliest type of male condom were made from animal products, and are considered high-end on the American markets today. The most common type of condoms sold and purchased today is the latex rubber condom and is available in lubricated or non-lubricated varieties.

Female Condoms: These type of condoms look very similar to the male condoms, but are actually inserted into the female instead of on the male. It is a single-use, pre-lubricated, polyurethane sheath that is also used before sexual intercourse. It has two rings--one that is inserted to the upper vagina and the other stays on the outside of the vagina and covers the vulva and surrounding area of the vagina. It is not as widely used due to the costliness of the materials.

Spermicides: Spermicides are chemicals that are used to kill sperm, and, therefore, not allowing them to enter the vagina and causing a pregnancy. In some cases, they can even kill some sexually transmitted diseases. They are available in the form of gels, jellies, foams, pessaries, and water-soluble films. Usually used in conjunction with other types of barriers, spermicides are safe in low amounts, as high dosages could damage the vaginal lining, sensitize the penis, and even help increase the chances of being infected with HIV.

The Sponge: Sponges can come in varying kinds and sizes. It is usually made of disposable and soft polyurethane and paired with a spermicide. It is a choice of contraception for women because it is very convenient--women just need to wet the sponge in water, insert into the vagina, and it would be effective for the next 24 hours, despite the number of sexual acts. Despite its convenience, it is still not as effective as other contraceptive techniques.

Cervical Cap: The rubber, metal, or latex cervical cap is a small, cup-like instrument that is placed on the cervix within the vagina. Spermicide can be placed within the dome to ensure that sperm is blocked physically as well as chemically. Some types of cervical caps must use suction with the vaginal walls in order to be in place during sexual intercourse. Since every cervix is different, every woman must be fitted by a medical professional properly. Few women actually use this method of barrier contraception because there are not many professionals that are trained in the fitting of the cervical cap. In the U.S., the FDA approved three types of the cervical cap--small, medium, and large. The small cervical cap is designed for women who have never gotten pregnant, the medium is for women who have had a miscarriage, abortion, or had birth by Caesarian section, and the large cap is for women who have had a live and natural birth.

Diaphragms: Like the cervical cap, the diaphragm is also a contraceptive barrier that is used at the cervix. This dome-shaped device can be made from latex or silicone and is expanded over a ring. There is a spring on the rim of the ring that also creates suction onto the vagina. Just like the cervical cap, the diaphragm is also needed to be fitted depending on the size of the cervix. The drawback to this method is that the diaphragm must be placed three hours before sexual intercourse.

Hormonal Methods

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Hormonal methods of contraception are used to impede fertilization and ovulation of an egg through the manipulation of ovarian hormones, such as progesterone and estrogen. These methods include oral contraceptives, intrauterine devices, injectables, implants, birth control patch, and vaginal contraceptive ring. Although these forms of contraceptives do help prevent unwanted pregnancies, they do not prevent sexually transmitted diseases.

Oral Contraceptives:

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Combined Oral Contraceptives: These contraceptives are available in the form of pills, which must be taken once everyday. The pill impedes the follicle-stimulating hormone (FSH) in the pituitary, which doesn't allow for the maturation of follicles in the ovaries. By the human body's feedback loop, the luteinizing hormone (LH) increases, which then prevents ovulation of eggs within the ovary. In addition to the decrease of ovulation, the increase of progesterone in the pill increases the cervical mucus, which creates a harsh environment for sperm. The two types of birth control pills include the combination progesterone and estrogen pill and the progesterone-only pill. Usually, women must orally take 20, 21, or 22 active pills, which contain a measured amount of combined progesterone and estrogen, and then followed by inactive sugar pills. During the time that the woman is taking the inactive pills, less menstrual bleeding would take place than if the woman was not on the pill. These pills imitate a normal, yet regulated, menstrual system. Examples of combined oral contraceptives include Yaz, Yazmin, Ortho Tri-Cyclen, Desogen.

Continuous-Use Oral Contraceptives: These pills also must be used everyday orally and contain a combination of progesterone and estrogen. The purpose of these pills is to decrease the number of menstrual periods and the duration of the periods within the year. With continuous-use oral contraceptives, women must take active pills for 12 weeks straight and then take 7 inactive pills. A drawback to this method is that women will experience breakthrough bleeding and spotting. An example of this type of contraceptive include Seasonique.

Progesterone-Only Pills: These pills only contain progesterone in order to increase the thickness of cervical mucus and decrease the infiltration of sperm. This method also utilizes once-a-day pills, just like combined oral contraceptives and continuous-use oral contraceptives. Many providers choose to prescribe this contraceptive to women who have experienced adverse side effects with the estrogen in the combined pills. Progesterone-only pills are not as effective as the combination pills.

Emergency (Postcoital) Contraception: This method of contraception is used orally and only once immediately after (approximately 24-36 hours) the woman has experienced unprotected sexual intercourse that may lead to an unwanted pregnancy. Yet, it may still be effective up to five days after unprotected sexual intercourse. This "Morning After Pill" only contains a dosage of 750 mg of levonorgestrel in each pill. It is meant to be a single use, and not continuously.

Intrauterine Devices:

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Intrauterine devices, or IUDs, are plastic devices placed within the cervix that could contain copper and/or release levonorgestrel and are used to inhibit sperm from reaching an implanted egg. Earlier versions of the IUDs had a copper-based branch to stabilize it within the vagina. With the more modern plastic variation, it was observed that as the size of the device increased, the menstruation became heavier, and women were more prone to vaginal infections if they ever had sexual contact with anyone with STDs. With this type of contraceptive, there are many risks that appear to outweigh the advantages.


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Injectables are a long-lasting and more efficient versions of the oral contraceptives. Injectables are available to women as 3-monthly intramuscular injection with a high dosage of medroxyprogesterone acetate (DMPA), or known as Depo-Provera, and as a 2-monthly intramuscular injection with a dosage of norethindrone enanthate, or NET-OEN. The only negative aspect with using injectables as a form of contraceptive is how to maintain a regular dose for a long period of time.

It is projected that the use of injectables will be more common in the future as compared to other methods of contraception. The progestin-only injectables are most likely going to be the most commonly used and offered, such as the 3-monthly DMPA and the 2-monthly NET-EN. In terms of the combined injectable, a monthly dose would be available. A 3-monthly injectable made with levonorgestrel butanoate is being improved, which works similarly to DMPA. With a 3-monthly dose, such as DMPA, the greatest advantage is that there is a low amount of synthesized chemicals circulated within the body, as well as faster and easier for women to stop taking the contraception in order to become fertile again. Also, less hormonal chemicals would result in less ovarian limitation and less risk of amenorrhea, or the lack or miss of one or more menstrual periods.

Depo-Provera is a type of long-acting hormonal method by injection that is very successful in its purpose of contraception, but is difficult to remove from the body and takes a longer time for the individual to become pregnant again. Norethindrone enanthate, a reduced progestogen version of Depo-Provera, provides a slight relief from the adverse side effects of Depo-Provera, but the woman would need to be injected every 2 months instead.

Side Effects of injectables as a form of long-acting contraception include large fibroids, amenorrhea, hypertension, diabetes, delayed return of ovulation, etc. In some cases, the continued use of injectables is associated with osteoporosis. These injectable preparations last so long that if the patient were to want to cease this form of contraception, it may take weeks to months in order for fertility to return once again. A main side effect of Depo-Provera is bone density loss over time. It is suggested for the patient to intake calcium supplements in order to counteract this side effect. Depo-Provera is not suggested to use for more than two years.

Subcutaneous Implants

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These implants provide a consistent and long-lasting method of contraception. Implants must be surgically placed subcutaneously and also removed from the same area. In terms of its structure, implants usually have a steroid placed inside of a capsule or rod. Because this form provides a steady dose of progestogens, implants usually contains a smaller amount of hormones than injectables and oral contraceptives. Surgical insertion and removal usually requires a professional and removal takes a longer time than insertion.


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Senanayake, P. (2008). Atlas of Contraception (2nd ed). United Kingdom: Informa UK Ltd.