I understand what y'all are saying, and trust me, I don't mean to be glib. It makes no more sense to legislate "proper use of opiates" to CP folks than it does to legislate "proper use of guns" to law-abiding citizens.
People who use illicit drugs will continue to do so. People who need PM will be denied.
People who murder, rape, deal or steal with guns will do so. People who are good and honest and decent will use their registered firearms to end their personal suffering.
It's not right, but it's REAL.
As for the potential for respiratory failure...I will no longer need my lungs (or my liver, etc.) when debilitating documented pain has caused me to hit the exit door.