4-Hydroxyamphetamine (4HA), also known as hydroxyamfetamine (INN and BAN), hydroxyamphetamine (USAN), oxamphetamine, norpholedrine, para-hydroxyamphetamine, and α-methyltyramine, is a drug that stimulates the sympathetic nervous system. It is used medically in eye drops to dilate the pupil (a process called mydriasis), so that the back of the eye can be examined. It is also a major metabolite of amphetamine and certain substituted amphetamines.