Famine can be solved by growing food or buying food. If opium is twice as valuable as potatoes then they could grow opium and buy twice as many potatoes as they could otherwise have grown.
Self reliance is important but generally less important than survival. If they don't have resources to treat opiate addicts they don't have to, the addicts are responsible for their own problems. We should try to help if we can but if we can't, we can't.
Poppy fields have legitimate uses, they are not just for producing street drugs. Heroin, morphine, codeine and others are products of the opium poppy and all of them are used medically. I also doubt this prohibition will make much difference in terms of drug addiction, they will get their drugs one way or another just like everywhere else.