Smack, horse, mud, brown sugar, junk, black tar, big H, dope, skag, dreck, mojo, white lady, brown. Users report feeling a rush of pleasure, accompanied by a warm flushing of the skin, a dry mouth, and heavy extremities. They then sink into a dreamy, pleasant, drowsy state in which they have little sensitivity to pain. Other effects included slowed and slurred speech, slow gait, dilated pupils, droopy eyelids, vomiting, as well as constipation.

Heroin is a white to dark brown powder or tar-like substance. It is a highly addictive drug obtained by chemically altering morphine, a major constituant of the poppy seed pod. Heroin is a "downer" that affects the brain's pleasure systems and interferes with the brain's ability to perceive pain. Heroin can be used in a variety of ways, depending on user preference and the purity of the drug. Heroin can be injected into a vein ("mainlining"), injected into a muscle, smoked in a water pipe or standard pipe, mixed in a marijuana joint or regular cigarette, inhaled as smoke through a straw (known as "chasing the dragon,") and snorted as powder via the nose.

Heroin causes a pleasant, drowsy state, in which all cares are forgotten and there is a decreased sense of pain (analgesia). Immediately after injection, the feelings are most intense. This feeling is described as similar to a sexual orgasm. After that, the sexual feelings diminish and there is a decreased sexual desire and performance.

Breathing slows, pupils are constricted and many users experience nausea and perhaps even vomit. Opiates also create tension in certain muscles in the gastrointestinal tract so much that the normal propulsive movements that move food along cannot operate effectively, hence their ability to cause constipation. Through a similar action, they can also cause difficulties in urination.

The poppy plant evolved to match the biology of their predator/pollinators by developing opium alkaloids, a compound that acts on a class of neurotransmitter receptors in the brain of mammals. Opiates act by binding to specific receptor molecules for the endorphin/enkephalin class of neurotransmittors in the brain. These are among the neurotransmittors that control movement, moods, and physiology. Heroin enters the brain more rapidly than other opiates but is then converted back to morphine once inside. Taking heroin is like all the endogenous opioid neurons firing at once.

Long-term effects of heroin appear after repeated use for some period of time. Chronic users may develop collapsed veins, infection of the heart lining and valves, abscesses, cellulites, and liver disease. Pulmonary complications, including various types of pneumonia, may result from the poor health condition of the abuser, as well as from heron's depressing effects on respiration. In addition to the effects of the drug itself, street heroin may have additives that do not really dissolve and result in clogging the blood vessels that lead to the lungs, liver, kidneys, or brain. This can cause infection or even death of small patches of cells in vital organs. With regular heroin use, tolerance develops. This means the abuser must use more heroin to achieve the same intensity or effect. As higher doses are used over time, physical dependence and addiction develop. With physical dependence, the body has adapted to the presence of the drug and withdrawal symptoms may occur if use is reduced or stopped. Withdrawal, which in regular abusers may occur as early as a few hours after the last administration, produces drug craving, restlessness, muscle and bone pain, insomnia, diarrhea and vomiting, cold flashes with goose bumps ("cold turkey"), kicking movements ("kicking the habit"), and other symptoms. Major withdrawal symptoms peak between 48 and 72 hours after the last and subside after about a week. Sudden withdrawal by heavily dependent users who are in poor health is occasionally fatal, although heroin withdrawal is considered much less dangerous than alcohol or barbiturate withdrawal.

sources:
Kuhn, Cynthia, Scott Swartzwelder and Wilkie Wilson. Buzzed : the straight facts about the most used and abused drugs from alcohol to ecstasy. New York: W.W. Norton, 1998.

"heroin" Britannica.com. Vers. 2001
1999-2001. Encyclopædia Britannica.
1 Sep. 2000
(http://www.britannica.com/eb/article?eu="41067"&tocid="0"&query=heroin)