As of 2009, there is only one birth control shot available, and that is Depo-Provera (generic name medroxyprogesterone acetate). It consists of high doses of progestin, which mimics the naturally occurring hormone progesterone, according to the Mayo Clinic.
Function
Depo-Provera is a contraceptive---its purpose is to help prevent pregnancy. It helps to prevent ovulation, which makes pregnancy unlikely to occur, and according to the Mayo Clinic, Depo-Provera is 97 percent effective.
Time Frame
Depo-Provera is given initially within five days after your menstrual period starts, and you need to get another shot every three months for the medication to be effective, according to FamilyDoctor.org. The shot is generally given in the buttock or upper arm.
Benefits
Besides helping prevent pregnancy, because this drug is progestin-only, you do not experience the side effects that birth control methods containing estrogen may have, like a higher risk of blood clots.
Side Effects
When taking Depo-Provera, your periods might be erratic, or you may not have a period at all. Other side effects can include weight gain, depression and breast tenderness. If used for a prolonged period of time, you might have some bone loss, which reverses once you stop this drug.
Considerations
When you stop Depo-Provera, your period may not return to normal for several months, or it may take several months for your period to return; this means your fertility may be delayed for a time while your body adjusts to being off the medication.
Warning
This medication does not protect against sexually transmitted infections or HIV/AIDS. It is only for use of preventing pregnancy.
