How long does it take for the Depo-Provera contraceptive injection to become effective against pregnancy?
Depo-Provera is an injectable contraceptive manufactured by Pharmacia and Upjohn. If the injection is given within the first five days of a girl’s period it becomes effective immediately. If it is given after this, an additional method of contraception such as a condom should be used for 7 days. The injection needs to be repeated every 12 weeks.