The hydrochloride salt of the synthetic central nervous system stimulant methylphenidate. Methylphenidate appears to activate the brain stem arousal system and cortex to produce its stimulant effect and, in some clinical settings, may improve cognitive function. Check foractive clinical trials using this agent. or A drug used to treat certain behavior disorders, such as attention deficit hyperactivity disorder (ADHD). It is also being studied as a way to improve brain function in patients treated with anticancer drugs. Methylphenidate hydrochloride acts on certain parts of the brain. It is a type of central nervous system stimulant. Also called Concerta and Ritalin.