How long is the injection designed to last? How often do you receive them?
This medication will not block the analgesia or sedation of opioids, but a lot of the mental euphoria from opioids is caused by downstream dopamine effects. It will block this, some of the euphoria, but not all of it.
Long form AP injections are a little different than basing it on the half life, as these injections stay "suspended" in your arm for weeks or months, and cannot be metabolized as they would be if taken orally.