Depo-Provera is a medication used to prevent pregnancy in women, as an alternate form of contraception or to relieve symptoms of pain by endometriosis. This drug requires a prescription and can be bought in both generic and brand forms. This medication works by preventing a woman's egg from fully developing a process that may result in a pregnancy. There are several brands on the market today. Check with your doctor or the product package for the correct dosage as it may differ from brand to brand.