What is heroin?
Heroin is an odorless, white crystallized compound, derived from morphine. It functions as a central nervous system depressant, causing the user to enter a dream-like state. Because of its chemical composition, it is estimated to be three times as potent as morphine.

What are the symptoms of someone under the influence of heroin?
Heroin restricts the user's respiration, impairs mental functioning, causes drowsiness and constricts the pupils. In keeping with the dream-like state the drug induces, users are generally lethargic, and may also become nauseous (overdoses are frequently fatal because the user chokes on his or her own vomit).
 

What are the potential dangers of using heroin?
Because production of the drug is not controlled (and sellers frequently "cut" the powder with non-narcotic ingredients), each use could cause a fatal overdose. Even non-fatal overdosing can lead to brain damage, leaving the user in a coma. "Shooting" heroin (injecting it into the bloodstream) is a major source of hepatitis and HIV transmission, because users often share needles.