Heroin is an extremely addictive drug derived from morphine, which comes from the opium poppy. After a brief euphoria, the user goes "on the nod," which is both a wakeful and drowsy state. A user's capacity to think critically gets clouded because heroin triggers depression of the central nervous system. Other effects include slowed and slurred speech, sluggish movement, constricted pupils, droopy eyelids, impaired night vision, constipation, and vomiting.
Using heroin can slow a driver's reaction time, cause visual distortions, and impair simple motor skills. In severe cases, heroin causes stupor, coma, and death.