It isn't your job to evaluate the doc's recommendation or to try to explain the doc's rationale to the irate patient. Neither is it your job to placate someone who is upset about not getting a refill on his pain meds. A patient who has been on a particular regimen for seven years is not going to be happy about having it changed against his will. That just goes with the territory.
It IS your job to develop good boundaries that allow you to treat the patient with courtesty while still sticking to the doc's plan. "I'm sorry you didn't get what you hoped for. Here is the phone number for the pain management clinic."
Do not engage any further than that.
"I need my meds. No one else gives me a hard time about getting a prescription."
"Sorry about that. You'll have to contact the pain management clinic."
"You just don't care. Nobody cares because I'm (old, black, on Medicare, disabled, Martian, made out of macadamia nuts, etc.).
"I'm sure it seems that way. I'm sorry I can't help you."
"Just let me see the doc."
"You'll have to contact the pain management clinic."
And so on.
If you have access to security, have them on speed dial. Otherwise, if threats are made or the patient won't leave, call the police.
YOU need to have a good sense of where the lines are drawn. It would be nice if the doc came out and did his own dirty work, and you can ask him to do that with someone who won't leave, but ultimately, the patients will size you up and see if you're too worried about being nice. They will push you around if you let them.
The only way to win is not to play. Repeat the mantra ("you'll have to call the pain management clinic.") fifty times if you have to, but the minute you try to convince an angry patient about anything else, you've already lost.
Google, "assertive," and you should find all kinds of tricks and techniques for standing strong. I wish you the best.