Building more jails shouldn't be necessary — but yes. Offer the choice of jail or rehab. (This is what e.g. Michael Shellenberger is calling for, as well as recovered drug addicts I know and respect.) This is has a dramatically better chance of saving the addict than does the status quo of bouncing them back from death with Narcan so they can do the same thing tomorrow… and the day after… and the day after… until they die.