Contraception (part 3): Contraceptive Injections, Subdermal Contraceptive Implants & Emergency Contraception

This section is a continuation of the first and second part series on contraception methods. To read the first and second part of this series, click here and here.

4.  Contraceptive Injections

Contraceptive injections are another very effective method of contraception. They contain the female hormone, progestogen.  Common formulations of this progestogen include;

• Depot medroxyprogestogen acetate for long term action.( Popular brand names include Depo-Provera and Sayanna Press)
• Depot norethisterone enantiate for short term action. (Popular brand names include Noristeral)

These progestogin containing injections are administered deep into the muscle or directly under the skin, which is then slowly released into blood circulation.  They are usually administered once every 12 weeks (Depot medroxyprogestogen preparations) or once every 13 weeks ( Depot norethisterone enantiate).

Contraceptive injections work in three ways;

• It stops the process of ovulation. The woman can no longer release eggs from her ovaries.
• It thickens mucus produced at the cervix making it difficult for sperm to get into the womb so as to fertilise the female egg
• It also thins the lining of the womb ( known as the endometrium). This prevents a fertilized egg from attaching and implanting itself to this lining.

Progestogen contraceptive injection are very effective methods of contraception. Statisics show observed pregnancy rate to be 0.1% at 1 year and 0.4% at 2 year interval. 

Compared to other forms of contraception, contraceptive injections offer the following advantages

• No need to take pills everyday. Injections are administed once every 3 months (on average).
• Injections can be used even while breastfeeding
• Contraceptive injections do not interrupt sex between couples
• The injections also offer other helpful benefits  such as resolving painful periods, heavy menstrual bleeding, premenstrual symptoms. It also reduces the chances of getting ovarian cancer.
• To stop using contraceptive injections, one simply waits for the effects of the last injection administered to wear off. No need for frequent visits to the doctor.

However, the following disadvantages should also be considered before using contraceptive injections. These include;

• Once administered, the injection cannot be removed. Side effects associated with use of contraceptive injections has to be borne by the user till the effects of the last administered injection wear off (13 weeks after administration of injection)
• Contraceptive injections disrupts the menstrual cycle. Within the first year of use, menstrual period may be very irregular with heavy flow, light flow, prolonged and even short blood flow. In some women, menstrual period stops altogether. Even after stopping the contraceptive injection, it might take a long time before menstrual periods return to normal (between 4 months to 1 year). 
• Because of the long acting nature of contraceptive injections, it takes considerable length of time after stopping the injections for the woman to start ovulating and hence, become fertile again (between 4 months - 12months).
• Contraceptive injections can increase the body weight and body mass index (BMI ) of the user.

Contraceptive injections are very potent contraceptive methods which can be used by most woman with few side effects. When side effects do occur, they usually settle over time as injections are administered. The main side effect of concern however is irregular menstrual periods due to its mechanism of action.

5.  Subdermal Contraceptive Implants

Subdermal contraceptive implants come as a small, tube-like device that is inserted under the skin. This implant contain a progestin hormone which is released into the blood stream at slow but even steady rates with the desired result of providing contraceptive action over long periods (usually within 1 to 3 years).

The progestin hormone contained in the implant stops the release of eggs from the woman's ovaries, in effect stopping ovulation and fertility. It also thickens the cervical mucus making it difficult for the sperm to get through to the womb. Another action of progestin hormone is to thin the lining of the womb making it almost impossible for a fertilized egg to implant itself onto this lining.

Subdermal contraceptive implants has an efficacy duration of up to 3 years and they remain in place, under the skin within the area of insertion. After 3 years, the implant needs to be removed and replaced with another if needed.

Subdermal contraceptive implants are a very effective method of contraception. They provide ease of administration and average contraceptive failure rate seen with this method is very low at 0.03%.

Most women can use the subdermal contraceptive implant as first choice contraceptive method. A few health risks though, may make some women ineligible for this method of contraception. These risks include;

• Being pregnant
• History of heart disease.
• History of stroke
• Migraines
• History of breast cancer
• Women at risk of osteoporosis
• Diabetes
• Women with thrombosis (blood clot in any blood vessel)

Advantages of having a subdermal contraceptive implant include;

• Long duration of action (up to 3 years). No need for everyday pills or any other method of contraception for 3 years.
• Can be used during breastfeeding
• Does not interrupt sex.
• Implant has the added benefit of reducing heavy menstrual blood flow and painful period cramps in women.
• It may also help protect agains bacterial infections and cancer of the womb because of it's thickening action on the cervical mucus.

Disadvantages of subderml contraceptive implants include;

• Disruption of the menstrual cycle. This is a major disadvantage of subdermal contraceptive implants. Within the first year of use, a common complaint by women who use subdermal contraceptive implant method is occurence of irregular menstrual bleeding.
• Women using subdermal implants could also experience mood swings
• Decreased libido (sex drive) in women.
• Acne
• Presence of breast tenderness.

6.  Emergency Contraception

Emergency contraception refers to the method of contraception used after unprotected sexual intercourse (not before).  This method of contraception must be used within 3 to 5 days after sex.

The are two types of emergency contraception available;

• Insertion of an intrauterine device (IUD) 
• Emergency contraceptive pills

The intrauterine device (IUD) can be inserted into the uterus up to five days after unprotected sex. It is a very effective method of emergency contraception as it stops the female egg from getting fertilised by the sperm. It also prevents implantation of a fertilized egg onto the lining of the womb. The intrauterine device can also be left on (an added advantage) for subsequent long term contraception. Interuterine device method of emergency contraception is a more effective form of emergency contraception than the emergency contraceptive pills.

Emergency contraceptive pills are popular methods of emergency contraception. There are two types of emergency contraceptive pills;

• Progestogin pill. This pill contain levonorgestrel. Popular brands of this type of emergency contraceptive pill are Levonelle and Postinor. They work by delaying ovulation and must be used within 72 hours after unprotected sex. They have no effect when an embryo has implanted onto the lining of the womb.
• Ulipristal Acetate pill. This pill contains Ulipristal acetate. It works by modulating progestin-receptors, thereby preventing ovulation. Ulipristal acetate is more effective as an emergency contraceptive pill than levonorgestrel. A popular brand of this type of emergency contraceptive pill is called Ellaone.

A major draw back to the use of emergency contraceptive pills is the effect the body weight of the woman has on its contraceptive action. Emergency contraceptive pills are less effective in obese women with a body mass index (BMI) value greater than 30. The only suitable emergency contraceptive option for such women is the Intrauterine device emergency contraceptive method.

NEXT IN THIS SERIES: INTRAUTERINE DEVICE & STERILIZATION

CREDITS & REFERENCE

(1) Drug Interaction with Hormonal Contraception: Faculty of sexual & reproductive healthcare (January 2012).
(2) Emergency Contraception; Nice CKS, November 2011
(3) Family Planning - Merck Manual (2013)