High dose stimulants in rats are neurotoxic. http://www.dr-bob.org/babble/neuro/20091104/msgs/931964.html Your mileage may vary, but I think prescribing patients >50mg amphetamine is often irresponsible. Ask your psychiatrist at what dosage he thinks amphetamine is neurotoxic. 90mg maybe? Doctors agree that a certain dose is neurotoxic but disagree on what that dosage is. 60mg is the official maximum safe dose, but it's not like you should put all of your trust in the FDA. Given clear stimulant burn-out I have noticed in multiple taking >50mg of amphetamine daily, I have no doubt that dosages like that cause negative neurological effects and that caution is merited in amphetamine dosing.
Stimulants aren't neurotoxic, specific substances at specific levels are. Methylphenidate's majority of benefit comes from its reuptake inhibition of both dopamine and norepinephrine. While it is also a dopamine releasing agent, it does so at dramatically lower levels than the amphetamine family. The difference turns out to be significant - while they both promote more dopamine activity in the brain, it turns out that preventing the disposal of brain chemicals is generally much safer than promoting their release. As far as I know there aren't real concerns about MPH neurotoxicity.
Methylphenidate and amphetamine is not the same thing, and I have not experienced anything like what you've said.
I really don't think burn-out is as common as people say, high-doses are more like in the 100+mgs, and that's not in anything that is considered therapeutic and extended release.
