Get rid of the dealers and they will quickly be replaced by other dealers. You need to get rid of the users and make the taking of drugs a possible life ending experience by spiking supplies with some accumulative poison.
How would you get it into the supply though ?
Cant see the distribution chain cooperating much.
Instead of seizing shipments that are found being smuggled into the country dope them and let them through as if you never detected them.
I suspect that this would be illegal in most all western democracies and most likely you don't really believe it is a viable option? However strict enforcement does work pretty well in some countries. Singapore I believe allows for caning and very long prison sentences.
If it was a simple problem with simple solutions then it would have been solved centuries ago.