"Reduce demand" has to be the most pathetic idea for a plan that I've ever heard. 
How do you change human nature?
Because that's what it'd take. People have been getting high or drunk or stoned for thousands of years .. what does that tell us except that a lot of people like it?
The sanest thing would be to reduce the demand for ILLICIT drugs by making a large number of various classes of drugs legal and to regulate their production and distribution.
Nobody would be dying from fentanyl-laced street heroin (or cocaine, or whatever) if they could buy the pharmaceutical grade product from a licenced dispensary.
And under legalization, the savings on policing and first responders could be put into treatment.
Of course, moral panic will prevent us from taking the sane route. So people will still die.
(And before anyone counters with price concerns -- these drugs are exceedingly cheap to manufacture in laboratory settings. The street price is inflated because of the risks to the dealer.)