Excerpt from Toxicity, Heroin

Synonyms, Key Words, and Related Terms: heroin, heroin toxicity, heroin poisoning, heroin addiction, heroin use, heroin dependence, dope, smack, skag, junk, mud, shill, big H, horse, white stuff, brown sugar, black tar, Lady Jane, body stuffers, body packers, intravenous drug use, intravenous drug abusers, IVDA, skin-popping, heroin overdose, diacetylmorphine, narcotic, mainlining, opioid

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Background: Heroin (diacetylmorphine) is a semisynthetic narcotic that was first synthesized in 1874. It was originally marketed as a safer, nonaddictive substitute to morphine. Soon after its introduction, heroin was realized to be clearly as addictive as morphine, prompting the US government to institute measures to control its use. By 1914, the Harrison Narcotics Act prohibited the use of heroin without a prescription. In 1920, the Dangerous Drugs Act prohibited the use of heroin altogether, thus driving it underground. In the United States, heroin remains the most frequently abused narcotic, followed by codeine and methadone.

In its pure form, heroin is a white powder with a bitter taste. Street heroin samples are frequently mixed with other substances so dealers may maximize their profits. Because of these impurities and additives, street heroin may appear in various hues and colors, ranging from white to dark brown. Heroin is occasionally sold as a black tarry substance, especially when crude processing methods are used to manufacture it.

The presence of impurities and additives also limits heroin absorption through mucous membranes, thus limiting its "rush" and "high" when it is sniffed or snorted. In patients who are dependent on heroin, intravenous injection ("mainlining") becomes the only effective method of heroin use. During the 1990s, the purity of US street heroin increased significantly, and its price sharply dropped. In 1980, for example, the average street sample (100-mg bag) contained 3.6% heroin (3.6 mg of heroin) and cost $3.90, compared with 1999, when the average street sample contained 38.2% heroin and cost $0.80. Samples from South America appeared to have the highest purity, reaching the 90% range. Not surprisingly, this dramatic increase in heroin purity, coupled with the well-publicized dangers of intravenous drug use, led to a change in the pattern of use. Snorting and smoking were the methods of choice and were especially favored by the younger users and new users. Recent samples, however, have demonstrated a rise in impurities. Analysis of heroin powder seized by the US Food and Drug Administration (FDA) in 2005 revealed a heroin content that ranged from 7.3-75%.

Heroin poisoning occurs when an individual accidentally or intentionally overdoses on the drug or when an ingested heroin packet ruptures in the GI tract of a "body packer" or "body stuffer."

Pathophysiology: Heroin is a highly addictive semisynthetic opioid that is derived from morphine. When used intravenously, heroin is 3-5 times more potent than its parent compound and is able to modulate pain perception and cause euphoria. Similar to morphine, heroin has mu, kappa, and delta receptor activity. In general, stimulation of the mu receptors results in analgesia, euphoria, CNS depression with drowsiness and reduced physical activity, respiratory depression, and miosis. Patients who are dependent on narcotics generally use heroin for its mu receptor–mediated euphoric effects.

Respiratory depression is the result of heroin’s ability to reduce the brain’s responsiveness to changes in PCO2 and hypoxia.

Miosis results from heroin’s effect on the mu and kappa receptors of the parasympathetic fibers that innervate the pupils. Stimulation of the delta and kappa receptors also results in analgesia, but the kappa receptors are mostly involved in spinal analgesia. Stimulation of kappa receptors may result in dysphoria and psychotomimetic effects.

Heroin, like morphine and other narcotics, also reduces peripheral vascular resistance (resulting in mild hypotension), causes mild vasodilation of the cutaneous blood vessels (resulting in flushing), and stimulates histamine release (resulting in pruritus).

Additionally, heroin inhibits baroreceptor reflexes, resulting in bradycardia, even in the face of hypotension.

Finally, heroin decreases gastric motility, in .....