Is depo-provera provera (medroxyprogesterone) a trustworthy contraception?

Yes: If the shots are taken at the appropriate times, yes.

Yes: Depo Provera (medroxyprogesterone) is a very effective form of birth control that is close to 99% effective in preventing pregnancy if injections are given on time. Injections are given every 3 months in your doctor's office. No pills to remember, no foreign bodies, and nothing to do prior to intercourse. It is a very reliable birth control option. Discuss this with your doctor.