And who's going to pay for hundreds of thousands of people to go through detox? And what's the plan after that? They'll still have access to street drugs.
The first thing we need is to stabilize the population and stop them from dying. The simplest, cheapest and most effective way--by far--would be to legalize and regulate the sale of these drugs.
This would destroy the black market drug trade, dramatically reduce policing, first response and other health-associated costs, and bring users out of the criminal realm so that they have no reason to fear getting the help they need.
Then we can develop a national health strategy to help people get off drugs... funded in whole or in part by the reduction in costs mentioned above.