Could there be some way to prevent it from affecting the neural system? As far as I know, drug stimulate certain neural chemical when it moves from cell to cell. If the receptor/ triggering process gets altered it should render drug useless. Of course if human have a far more powerful secondary neural system we should be immune to drug to a greater degree. And thus we eliminate a whole market and we all get to be in a drug free world. But then maybe some people need to be controlled for society to function, or maybe it's just fun to set everything on fire.