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temporarily and long-term. Heroin is a semisynthetic opiate derived
from dried sap of the opium poppy. Also derived from poppy, though
not synthesized, are morphine and codeine.

Heroin can be injected, smoked, swallowed or snorted. Intravenous
injection produces the greatest intensity and most rapid onset of
euphoria. Effects are felt within seconds. Even though effects for
sniffing or smoking develop more slowly, beginning in 10 to 15
minutes, sniffing or smoking heroin has increased in popularity
because of the availability of high-purity heroin and the fear of sharing
needles. Also, users tend to mistakenly believe that taking heroin in
ways other than IV use will not lead to addiction.

After ingestion, heroin rapidly crosses the blood-brain barrier. The
blood-brain barrier is basically a layer of tightly packed cells that
make up the walls of brain capillaries and prevent substances (i.e.
toxins) in the blood from entering into the brain. These cells
selectively filter out the molecules that are allowed to enter the brain,
creating a more stable, nearly toxin-free environment. However, all
psychoactive drugs freely pass the blood brain barrier and enter the
brain.

While in the brain, heroin is converted to morphine, which rapidly
binds to opioid receptors. Users tend to report feeling a “rush” or a
surge of pleasurable sensations. The feeling varies in intensity
depending on how much of the drug was ingested and how rapidly the
drug enters the brain and binds to the natural opioid receptors. The
rush is usually accompanied by a warm flushing of the skin, dry
mouth, and a heavy feeling in the user’s arms and legs. Following the
initial effects, the user will be drowsy for several hours with clouded
mental functioning and slow cardiac function. Breathing is slowed,
and can possibly slow to the point of death.

Repeated use of heroin produces physical dependency, which means
the development of tolerance to the drug’s effects that necessitates
ever larger amounts of the drug to achieve the same effect. A
characteristic withdrawal syndrome upon abrupt cessation of use also