Implants and injections: Alternative contraceptive methods

January 18, 2013

Contraceptive implants and injections are hormonal contraception. Unlike the combined oral contraceptive (COC) pill, they contain only progestogens that are similar to the hormone, progesterone, produced by the ovaries. They are long-acting, effective contraceptive methods.

These implants and injections release progestogens continuously and steadily into the bloodstream, which thickens the mucous in the cervix, thereby preventing sperm from entering the uterus.

The progestogens also make the lining of the uterus thin, thereby making it less receptive to the implantation of a fertilised egg on it. It also prevents the release of an egg from the ovaries (ovulation).

They are a reliable and reversible contraceptive method that is suitable for women who want to use hormonal contraception but do not want to take oestrogens, or who have conditions which make them unsuitable for the COC.

The implants and injections are very effective as they are more than 99 per cent reliable, ie less than one in 100 women who use it will get pregnant each year.


The primary advantage of contraceptive implants and injections is that they provide protection against pregnancy soon after the implant is inserted (or the first injection is given).

They are long-acting, and fertility returns to normal after its use is stopped.

Implants are effective for about three or five years, and each injection for eight or twelve weeks.

The advantages of implants and injections are that they do not affect the sexual act, and are options for those who are cannot use contraceptive methods that contain oestrogen, ie COC, contraceptive or vaginal ring. Implants and injections can be used during breastfeeding as it does not affect the latter. They may provide some protection against cancer of the endometrium and pelvic inflammatory disease, due to the thickening of the cervical mucous (which may prevent bacteria from entering the uterus).

Implants may reduce heavy or painful periods after about a year of use. Injections may reduce heavy, painful periods, and relieve premenstrual symptoms in some women.


There may be some disadvantages of contraceptive implants and injections that have to be considered.

They do not provide protection against sexually transmitted infections (STIs). They may cause periods to change significantly in the first year of use, becoming irregular, heavy, light and short, or stopping altogether (amenorrhoea).

The altered periods usually settle down after about a year of use, but they can sometimes continue for as long as the implant is fitted, or the injected progestogen remains in the body.

These changes are not harmful, but some women do not find them acceptable. Additional medicines may be prescribed if there is prolonged bleeding.

The effects on periods usually resolve soon after the removal of the implant.

However, it usually takes between eight to 12 weeks for injected progestogens to leave the body, so disrupted periods will continue during this time, and for some time afterwards. It can take between three months and a year for the periods to return to normal.

Users of contraceptive implants and injections may also have headaches, acne and tender breasts. Users of injections may also have mood changes and loss of sex drive (libido). These side effects usually resolve after a few months, but if they persist, medical attention should be sought.

Rarely, infection may occur at the site of insertion of the implant or injection, for which antibiotic treatment may be necessary. There is also a very rare risk of allergic reaction to the injection.

Injections may be associated with weight gain of about two to three kg over a year, although some women may lose weight.

They can cause thinning of the bones, but this does not increase the risk of bone fracture. The bone replaces itself when the injections are stopped, so it is unlikely that the injections will lead to long-term problems.

Women who are at increased risk of developing osteoporosis will usually be advised to use another contraceptive method.

Implants and injections are unsuitable for women who may be pregnant, want to have regular periods, or who have bleeding between periods or after sexual intercourse. They are also unsuitable for women who have had a clot in a blood vessel (thrombosis), breast cancer (currently or previously), migraine or liver disease.

The injection is unsuitable for women who have diabetic complications, liver cirrhosis, or who are at increased risk of developing osteoporosis.


Contraceptive implants contain either levonorgestrel or etonogestrel.

The levonorgestrel implant comprises six small silicone rods that are inserted, by the doctor, just below the skin of the upper arm under local anaesthesia. The small wound is then covered with a dressing, usually without the need for stitches.

The rods, which are left in place for up to five years, constantly release a small amount of levonorgestrel into the bloodstream. It is immediately effective if inserted on the first day of the period.

The etonorgestrel implant is a single rod that is inserted in a similar manner as the levonogestrel implant. The rod, which is effective for three years, releases etonorgestrel in a steady and controlled manner during this time. Its insertion and removal is faster than that of levonorgestrel implants.

Implants may be used until menopause, the average age of which is about 50 years.

As long as the implants are used in accordance with their duration of action, there is very effective protection against pregnancy, with 0.1 pregnancies in 100 women in one year of use.

An implant can be removed at any time by a doctor. The removal takes a few minutes under local anaesthesia. Upon removal, there is no longer any protection against pregnancy and the normal menstrual cycle is usually restored rapidly.


Contraceptive injections contain either depot medroxyprogesterone acetate (DMPA) or norethisterone enanthate (NET-EN). There are other injections that contain both oestrogen and progestogen, but these are not available in Malaysia.

The site of the injection is usually the muscle of the buttock, or sometimes, the upper arm.

DMPA injections are given every twelve weeks. The first three NET-EN injections are given at eight-weekly intervals, after which the injections are given every 12 weeks.

Disruptions of the period are not uncommon. There is amenorrhoea in about 45 to 50 in 100 women after the injections have been used for more than a year.

It may take up to a year for periods to start again in some women. This may be acceptable to some women, but others, especially those who want a pregnancy at a later date, may find this unacceptable.

As long as the injections are used in accordance with the prescribing directions, there is very effective protection against pregnancy, with 0.3 pregnancies in 100 women in one year of use.

About 70 per cent of women gain weight with DMPA, with an average of 2.5kg after one year of use. About 20 per cent of women gain weight with NET-EN, with an average of 5kg after one year of use.

About 70 per cent of women conceive within a year of stopping DMPA or NET-EN.

There have been concerns raised about the link between DMPA and cancer. However, data from the World Health Organisation suggest that there is no long-term increased risk of breast, cervical and ovarian cancer.

On the other hand, there is a marked reduction in the risk of endometrial cancer.

Timing it

Contraceptive implants or injections can be inserted or given at any time in the menstrual cycle, provided the user is not pregnant.

Implants and injections that are inserted or given during the first five days of the onset of periods, or within 21 days of childbirth in non-breastfeeding mothers, provide immediate protection against pregnancy.

If inserted or injected at any other time of the menstrual cycle or after 21 days of childbirth, there will be no protection for the following seven days; so another contraceptive method, eg condoms, will have to be used during this time.

There are reports of heavy and irregular bleeding when injections are given within the first few weeks after childbirth.

Injections are usually given six weeks after childbirth for breastfeeding mothers.

Implants can be inserted immediately after a miscarriage or abortion, with immediate protection against pregnancy.

Implants and injections are useful contraceptive methods. They provide excellent protection against pregnancy when used in accordance with the prescription directions. They can be used by most healthy women except those who have conditions which render them unsuitable.

Dr Milton Lum is a member of the board of Medical Defence Malaysia.

Source: The Star/Asia News Network

Category: Wellness and Complementary Therapies

Comments are closed.