There are no universally accepted definitions of the expressions, “narcotic drug and “psychotropic substance”. The expression “narcotics” has originated from the Greek word “narkoticos” the meaning of which is “benumbing or deadening. The expression narcotic’ is generally used to refer to a class of drugs that are central nervous system depressants, which produce insensibility or stupor. The expression narcotic” as ordinarily used refers to opioids i.e. opium, the derivatives of opium, and their semi-synthetic or wholly synthetic substitutes. Certain substances grouped as narcotic drugs either in the Single Convention on Narcotic Drugs, 1961 or in the NDPS Act are pharmacologically not narcotic drugs but belong to certain groups of psychoactive substances like stimulants, hallucinogens etc. For example, cannabis and cocaine come under the purview of the Single Convention on Narcotic Drugs. 1961. Under the NDPS Act, they are classified as narcotic drugs. However pharmacologically they do not belong to the group narcotics. While cocaine belongs to the group of stimulants, cannabis is a drug of its own class. It is more akin to the group of hallucinogens than to the group of narcotics.
The expression psychotropic substance is derived historically rather than pharmacologically in its connotation. The drugs grouped as psychotropic substances either in the Convention on Psychotropic Substances, 1971 or in the NDPS Act do not have any common characteristics which justify their grouping as psychotropic substances as distinguishable from the group of narcotic drugs. It was the international concern against increase in cases of poisoning brought out by amphetamines, a group of stimulants in many parts of the world that brought out the Convention on Psychotropic Substances, 1971.