Contraception: injection
Injectable contraceptives currently available to women in Australia are Depo-Provera and Depo-Ralovera. The active ingredient in both of these products is a synthetic hormone called DMPA, which is short for depo medroxyprogesterone acetate. DMPA is a progestogen, which is a synthetic form of the natural hormone progesterone.
Clinical trials are also being conducted at Melbourne’s Prince Henry’s Institute of Medical Research on an injectable contraceptive for men. However, its efficacy and side effects have not yet been determined.
How does it work?
Following injection into the muscle, DMPA is slowly released into the blood. It works by preventing ovulation (the release of an egg), as well as making the cervical mucus thicker (thus making it very difficult for sperm to enter the uterus) and makes the lining of the womb thinner (preventing the implantation of a fertilised egg).
How effective is it?
DMPA is 99 per cent effective.
What are the advantages?
Some of the advantages of DMPA are that it:
- is long-lasting, requiring only one injection every 3 months;
- is highly effective and reliable;
- helps protect against uterine cancer, pelvic inflammatory disease, ectopic pregnancy and ovarian cysts;
- is safe after childbirth and while breast feeding; and
- does not interfere with sexual intercourse or require daily pill-taking.
What are the disadvantages?
Some of the disadvantages of DMPA.
- It may take up to 12 months (sometimes longer) for fertility to return after the last injection.
- It cannot be used by women with blood clots, breast cancer, liver problems, or unexplained uterine bleeding.
- It may not be good for women with severe high blood pressure, diabetes or depression.
- It may produce side effects such as irregular bleeding or no periods at all — in fact half the women using it will have no bleeding after using it for a year.
- It may produce rare side effects, such as loss of libido (sex drive), weight gain, headaches, vaginal dryness, mood changes or bone mineral loss.
- It is long-acting: any adverse side effects may continue for 3 months.
How is it used?
A health care professional gives the injection into the upper arm or buttock every 3 months. The first injection is usually given during the first 3 days of your period, to ensure that you are not pregnant. It can also be given 6 weeks after giving birth, or immediately after an abortion. You should not use this method of contraception if you want to become pregnant within one to 2 years because sometimes the return of fertility can be delayed.
Last Reviewed: 01 May 2002
