Narcotics a group of drug substances when administered, diminish the perception of sensory impulses by the brain. This action reduces or stops the feeling of pain. Thus they are therapeutically useful as pain-relieving agents or analgesics. But their use as analgesics is complicated by a number of undesirable side effects. Derived from the Greek word for stupor, the term narcotic at one time referred to any drug that induced sleep. It is now generally used to refer to a wide variety of abused substances, particularly those derived from, or related to the chemical constituents of opium, cannabis, ammania (muscarine) and some solanaceous plants. However, most of the generally used narcotics are related to the opiates, the drugs that are derived from opium. Opium is a gummy exudate obtained from the mature but unripe capsules of the opium poppy, Papaver somniferum. The opiates include alkaloids like morphine, codeine, thebaine and a wide variety of semi-synthetic chemical compounds derived from them. These include substances like heroin (diacetyl morphine), dihydromorphine, oxymorphone, meperidine, alphaprodine, anileridine, piminodine, methadone, levorphanol, etc.

Narcotics derived from cannabis include substances like ganja, bhang, charas, marijuana, and hashish and chemical compounds like cannabinol, tetrahydrocannabinol, cannabidiol, etc and those derived from solanaceous plants include stramonium, hyoscyamus, mandrake and their tropane alkaloids such as atropine, hyoscyamine and hyoscine.

The predominant pharmacological effect of the narcotics is on the central nervous system. From the standpoint of medicinal use, their most important action is relief of pain. But this analgesic effect of the narcotics is often associated with a variety of undesirable side-effects such as drowsiness, euphoria, changes in mood, mental clouding, respiratory depression, hypotension, nausea and vomiting, inhibition of defecation and urination, and alterations of the endocrine and autonomic nervous systems. These effects are dose-related and vary from narcotic to narcotic. In higher doses all narcotics produce deep sleep and eventually general depression of all brain functions. Differences among the various narcotics lie in the potency of their action and in the degree and variety of the side effects which they cause. Repeated use of the narcotics develops tolerance and physical dependence or addiction. Heroin is one of most dangerous and highly addicting narcotics. Because of this addicting effect, most of the narcotics are not generally used as therapeutic agents. [Abdul Ghani]

See also hemp; opium; tobacco.