For a less dire example, when people stop making progress in physical therapy, insurance stops paying for it. Not because there is no chance they will benefit from further therapy, but to control costs.
But the important point is what exactly is making this drug scarce for local authorities. Opiod addicts are not rapidly consuming all the reserves of the drug on earth; companies have just set high prices and left the people to take the burden.
Accepthing that this resource is scarce for governments means inherently agreeing with the price set by the pharmaceutical company - and I don't think that's what we should do at all.
For a less dire example, when people stop making progress in physical therapy, insurance stops paying for it. Not because there is no chance they will benefit from further therapy, but to control costs.