What happens in a community when a heavily addictive drug is suddenly cut off?

For example: https://www.mercurynews.com/2023/04/28/will-an-s-f-style-fentanyl-crackdown-happen-in-san-jose/

What happens to addicts who will experience severe, painful, and dangerous effects if the drugs are suddenly cut off? The story says it targets the vendors and suppliers, not the addicts; but when the supply goes, what happens to the desperate, dependent user?

I don’t want to live in a world plagued with the horror of fentanyl, but I do. And I do not want to suddenly see my community ravaged by desperate, strung-out, and potentially lethally deprived addicts, or find them dying in the streets. Our kids.

Is this really the only way?