Methylphenidate is similar in action to amphetamines but is not an amphetamine. These meds in therapeutic dose do not cause dependence, etc. It is abuse of these types of substances (much higher doses and different routs of administration than oral) that causes issues.
Most things have a beneficial amount and too much is bad:
Tylenol (acetaminephen) is a useful pain releiver at therapeutic dose, but at higher dose it is highly toxic to the liver.
Water is needed to sustain life but too much can kill you.
vickie39108.3546990741