I'm sorry you're going through this.
I know it's a tough thing to do, but if they're threatening suicide you may want to call 911. If they were 5150'd they'd get food and water, and a little break from drugs.
But I realize that's easier said than done, you'd have a whole lot of resentment and anger to deal with afterward. Then again, you will, anyway, for refusing to enable them anymore.
Wishing you peace.