Injected Contraception

Injected contraceptives are given once every 3 months. Most injectables are progestin-only. In the United States, depo-medroxyprogesterone acetate (Depo-Provera) is the only approved injected contraceptive. Depo-Provera (also called Depo or DMPA) uses a progestin called medroxyprogesterone. Like other progestin contraceptives, Depo-Provera prevents pregnancy by halting ovulation, thickening the cervical mucus, and stopping the implantation of fertilized eggs in the uterine lining.

Depo-Provera is very effective in preventing pregnancies. About 3 in 100 women who use it become pregnant. However, Depo also carries the risk for many mild and serious side effects. The most serious side effect is loss of bone density (see Disadvantages ). Because of this complication, Depo-Provera should not be used for more than 2 years.

Administering Injections:

A physical examination is necessary before beginning the injections.
Depo is injected into a muscle in the patient's arm or buttock. During months between injections, the hormone slowly diffuses out of the muscle into the bloodstream.
Depo requires an injection by the doctor once every 3 months.
If more than 2 weeks pass beyond the regular injection schedules, the woman should have a pregnancy test before receiving the next injection.
Candidacy
Because Depo-Provera does not contain estrogen, it is safe for many women who are not candidates for combination OCs, such as women smokers over age 35.

Depo-Provera should not be given to women who have a history of:

Current or past breast cancer
Stroke or blood clots
Liver disease
Epilepsy, migraine, asthma, heart failure, or kidney disease (due to the fact that the drug causes fluid retention)
Unexplained vaginal bleeding
Risk for osteoporosis
Because of the long lag time between ending treatments and restoration of fertility, Depo-Provera is not recommended for women who are thinking of becoming pregnant within 2 years.

Advantages of Depo-Provera
Provides highly effective reversible protection against pregnancy without placing heavy demands on the user's time or memory
Does not increase risk for breast, ovarian, or cervical cancer. May protect against endometrial cancer.

May be useful for women with painful periods, heavy bleeding (including heavy bleeding caused by fibroids), premenstrual syndrome, and endometriosis
Disadvantages and Complications of Depo-Provera
Weight gain. Most women gain an average of 5 - 8 pounds.

Other common side effects include menstrual irregularities (bleeding or cessation of periods), abdominal pain and discomfort, dizziness, headache, fatigue, nervousness.
Most users of Depo-Provera stop menstruating altogether after a year. Depo can cause persistent infertility for up to 22 months after the last injection, although the average is 10 months.

Long-term (more than 2 years) use of Depo-Provera can cause loss of bone density. In November 2004, the FDA added a “black box” warning to the Depo-Provera label advising of this risk. The warning notes that the decline in bone density increases with duration of use and may not be completely reversible even after the drug is discontinued. Based on this information, the FDA recommends that Depo-Provera should not be used for longer than 2 years unless other birth control methods are inadequate. A 2005 study of young women (age 14 - 18 years) found that adolescents who stop taking Depo-Provera do regain bone density.

The injections do not provide protection against sexually transmitted diseases. According to a 2004 study, women who take Depo-Provera have three times the risk of acquiring chlamydia and gonorrhea as women who do not use a hormonal contraceptive. The reason for this increased risk is unclear. The same study found that oral contraceptive use, in comparison to non-hormonal contraceptives, was not associated with increased risk.