Birth Control Shot Side Effects

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The birth control shot Depo-Provera is a progestin-only contraceptive that is given by injection every 12 weeks. It contains a synthetic progestin called medroxyprogesterone acetate that remains in the body for a long period of time after the injection is given. This method of birth control is controversial among women because of its reputation for causing unpleasant side effects.

Function

  • The birth control shot works by preventing ovulation and thickening cervical mucus. The high dosage of progestin causes a woman’s body to act as if it is pregnant; many of the side effects associated with this method of birth control are similar to those experienced during pregnancy. Unlike birth control pills, Depo-Provera does not contain estrogen, so it does not typically cause nausea and vomiting. The lack of estrogen in Depo-Provera also reduces the amount of uterine lining (endometrium) that builds up each month, so many women experience fewer periods or no periods at all while using the birth control shot.

Effects

  • The most common side effects associated with the birth control shot are weight gain, changes to the menstrual cycle, depression, decreased interest in sex, breast tenderness, acne and headaches. Many of these side effects are extremely common; after one year of use, approximately 70 percent of women have gained weight and 50 percent have stopped having periods.

Significance

  • Studies released in 2004 led to the inclusion of a black box warning on Depo-Provera. Black box warnings are used to inform doctors and patients of a serious risk associated with the use of a prescription medication. The black box warning on Depo-Provera states that the use of this contraceptive causes a loss in bone density, increasing the risk of osteoporosis. Bone density losses associated with the birth control shot are more significant in teenagers and women who use this method of contraception for more than two years.

Benefits

  • Although the side effects of the birth control shot can be very unpleasant, this method of birth control does offer some advantages over other methods. Depo-Provera is considered safer to use while breastfeeding than birth control pills are, which make it a good choice for women who have given birth recently. Since the birth control shot is only administered once every 12 weeks, it is useful for women who have difficulty remembering to take birth control pills. Many women choose to try Depo-Provera in the hopes that they will stop having periods, but this effect is far from guaranteed. Some women who use the birth control shot find that they have longer, heavier or more frequent bleeding.

Considerations

  • Because the birth control shot can cause unpleasant and sometimes serious side effects, its use is not recommended for some women, and most women should not use this method of birth control for more than two years. Depo-Provera contains the same hormone in the now-discontinued birth control implant, Norplant, and so should not be used by women who experienced significant side effects while using Norplant. Depo-Provera’s side effects can last for up to six months after the last shot is given. Some doctors prescribe a trial of progestin-only birth control pills (the “mini-pill”) to find out what side effects a woman might experience while taking Depo-Provera.
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