Heroin is a highly addictive white or brown powder or brown sticky tar made from opium poppies. Users may snort, smoke or inject it. Heroin is a depressant. It enters the brain, where it is converted to morphine and binds to receptors known as opioid receptors. These receptors are located in many areas of the brain that deal with pain but also within the brain stem — important for automatic processes critical for life, such as breathing, and blood pressure. Heroin overdoses frequently involve a suppression of respiration. Heroin use can cause death by respiratory failure. Several factors can increase the risk of overdose, including the strong tolerance effects that develop with repeated use. Tolerance effects wear off over time, and users who take a break may find that a previously-safe dose is now dangerously large.
The purity of street heroin is also highly variable (and may have risen in recent years) and users often do not know how much heroin they are taking. Street heroin is frequently impure, and some adulterants are dangerous. Several hundred heroin users died in 2006 in the U.S. after unwittingly taking heroin cut with fentanyl, a powerful synthetic opiate.
Risks
Warm flushing of the skin / Dry mouth / Heavy feeling in the extremities / Nausea / Vomiting / Severe itching / Clouded mental functions / Infectious diseases, including HIV/AIDS and hepatitis (from injection needles) / Collapsed veins / Infection of the heart lining and valves / Abscesses at the injection location / Liver or kidney disease