Opium, narcotic drug produced from the drying resin of unripe capsules of the opium poppy, Papaver somniferum. Opium is grown mainly in Myanmar (formerly Burma) and Afghanistan. Worldwide the amount of opium distributed illegally exceeds legitimate demands for it.

In its commercial form, opium is a chestnut-colored globular mass, sticky and rather soft, but hardening from within as it ages. It is processed into the alkaloid morphine, which has long served as the chief painkiller in medical practice, although synthetic substitutes such as meperidine (trade name Demerol) are now available. Heroin, a derivative of morphine, is about three times more potent. Codeine is another important opium alkaloid.

The molecules of opiates have painkilling properties similar to those of compounds called endorphins or enkephalins produced in the body. Being of similar structure, the opiate molecules occupy many of the same nerve-receptor sites and bring on the same analgesic effect as the body's natural painkillers. Opiates first produce a feeling of pleasure and euphoria, but with their continued use the body demands larger amounts to reach the same sense of well-being. Withdrawal is extremely uncomfortable, and addicts typically continue taking the drug to avoid pain rather than to attain the initial state of euphoria. Malnutrition, respiratory complications, and low blood pressure are some of the illnesses associated with addiction.

As long ago as ad 100, opium had been used as a folk medicine, taken with a beverage or swallowed as a solid. Only toward the middle of the 17th century, when opium smoking was introduced into China, did any serious addiction problems arise. In the 18th century opium addiction was so serious there that the Chinese made many attempts to prohibit opium cultivation and opium trade with Western countries. At the same time opium made its way to Europe and North America, where addiction grew out of its prevalent use as a painkiller.

With the invention of the hypodermic syringe during the American Civil War (1861-1865), the injection of morphine became indispensable in treating patients who had to undergo some of the newly developed surgical operations. Physicians of that time hoped that injecting morphine directly into the blood stream would avoid the addictive effects of smoking or eating opium, but instead it proved more addictive. With the discovery of heroin in 1898 came a similar hope, but this more potent drug created a much stronger dependency than opium or morphine.

Opium is sold on the street as a powder or dark brown solid and is smoked, eaten, or injected. Although the synthetic narcotic methadone has been used to offer addicts some relief from opiates, it is itself addictive. Complete recovery from opiate addiction requires years of social and psychological rehabilitation. See Drug Dependence.