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 oral contraceptives, 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.