When heroin is taken orally it undergoes a metabolic process that parallels the systemic delivery of morphine. However, part of the severity of heroin as an addictive substance is that when the drug is injected, it avoids this first-pass metabolic effect, and very rapidly crosses the blood-brain barrier and acts more directly on the brain. Brain chemistry results in the drug’s euphoric, pain relieving and anti-anxiety effects, which are psychologically and physically addictive.

Heroin is known for the transcendent relaxation and the intense euphoria it induces. As an illegal substance, the heroin addict cannot be certain of the dosage, purity or exact content of the drug, leading to many fatalities. Shared needles fuel the spread of HIV and hepatitis among injecting addicts.

Heroin is used illegally by snorting or smoking by inhaling its vapors when heated, rolled with tobacco in a cigarette or by heating the drug into an injectable liquid. Pure heroin is a white, powdery substance. Impure heroin may be brown. Heroin is sometimes wrapped in small plastic bags or paper-wrapped packages.

Discarded needles may be a sign of heroin addiction or another drug abuse. Drug paraphernalia includes razor blades, straws, pipes and rolled up pieces of paper.