Stimulant. Methylphenidate is classified as a stimulant, even though it does not produce "stimulantion" in child with or without adhd. Other stimulants are amphetamine and methamphetamine and modafanil, plus one (pemoline) that now is off the market. All are thought to act by increasing brain Dopamine activity, but the exact effects on the brain are more complex than that.
FDA classification . Mph is a a class ii controlled substance because of it's high potential for abuse. Mph "stimulates" the part of the brain that inhibits behavior by reducing the rapid re-uptake of Dopamine when the Dopamine transporter protein is " hyperactive." this allows the brain's own Dopamine to stay in the synapse, the space between neurons, longer, which improves sustained attention.