A drug is any substance that causes a change in an organism's physiology or psychology when consumed. Drugs are typically distinguished from food and substances that provide nutritional support. Consumption of drugs can be via inhalation, injection, smoking, ingestion, absorption via a patch on the skin, or dissolution under the tongue.

Medical Drugs:

In pharmacology, a drug is a chemical substance, typically of known structure, which, when administered to a living organism, produces a biological effect. A pharmaceutical drug, also called a medication or medicine, is a chemical substance used to treat, cure, prevent, or diagnose a disease or to promote well-being.

Traditionally drugs were obtained through extraction from medicinal plants, but more recently also by organic synthesis. Pharmaceutical drugs may be used for a limited duration, or on a regular basis for chronic disorders.

A medication or medicine is a drug taken to cure or ameliorate any symptoms of an illness or medical condition. The use may also be as preventive medicine that has future benefits but does not treat any existing or pre-existing diseases or symptoms.

Dispensing of medication is often regulated by governments into three categories-over-the-counter medications, which are available in pharmacies and supermarkets without special restrictions; behind-the-counter medicines, which are dispensed by a pharmacist without needing a doctor's prescription, and prescription only medicines, which must be prescribed by a licensed medical professional, usually a physician.

In the United Kingdom, behind-the-counter medicines are called pharmacy medicines which can only be sold in registered pharmacies, by or under the supervision of a pharmacist. These medications are designated by the letter P on the label. The range of medicines available without a prescription varies from country to country.

Medications are typically produced by pharmaceutical companies and are often patented to give the developer exclusive rights to produce them. Those that are not patented (or with expired patents) are called generic drugs since they can be produced by other companies without restrictions or licenses from the patent holder.

Pharmaceutical drugs are usually categorised into drug classes. A group of drugs will share a similar chemical structure, or have the same mechanism of action, the same related mode of action or target the same illness or related illnesses.

There are numerous governmental offices in many countries that deal with the control and oversee of drug manufacture and use, and the implementation of various drug laws. The Single Convention on Narcotic Drugs is an international treaty brought about in 1961 to prohibit the use of narcotics save for those used in medical research and treatment.

The international conventions on drug addiction limit the production, manufacture, sale and consumption of drugs except for medical research and treatment purposes.

Narcotic Drugs:

The term narcotic is of Greek origin which means to make numb, originally referred medically to any psychoactive compound with sleep-inducing properties. However the term narcotic has become associated with opiates and opioids, commonly morphine and heroin, as well as derivatives of many of the compounds found within raw opium latex.

Legally speaking, the term narcotic is imprecisely defined and typically has negative connotations. When used in a legal context, a narcotic drug is one that is totally prohibited, such as heroin, or one that is used in violation of governmental regulation. In the medical community, the term is more precisely defined and generally does not carry the same negative connotations.

Statutory classification of a drug as a narcotic often increases the penalties for violation of drug control statutes. The INCB Yellow List is a document that contains the current list of narcotic drugs under international control and additional information to assist governments in filling in the International Narcotics Control Board questionnaires related to narcotic drugs, namely, form A, form B and form C. In the context of international drug control, narcotic drug means any drug defined as such under the 1961 Convention.

In India, the NDPS Act 1985 defines narcotic drug under sub-clause (xiv) of section (2) as narcotic drug means coca leaf, cannabis (hemp), opium, poppy straw and includes all manufactured drugs.

The term coca leaf appearing in the definition of narcotic drug is defined in sub-clause (vi) of section 2 of the Act as follows:
coca leaf means:

1. the leaf of the coca plant except a leaf from which all ecgonine, cocaine and any other ecgonine alkaloids have been removed;
2. any mixture thereof with or without any neutral material, but does not include any preparation containing not more than 0.1 per cent. of cocaine

The term cannabis appearing in the definition of narcotic drug is defined under sub-clause (iii) of section 2 of the Act as follows:
cannabis (hemp) means:

1. charas, that is, the separated resin, in whatever form, whether crude or purified, obtained from the cannabis plant and also includes concentrated preparation and resin known as hashish oil or liquid hashish;
2. ganja, that is, the flowering or fruiting tops of the cannabis plant (excluding the seeds and leaves when not accompanied by the tops), by whatever name they may be known or designated; and
3. any mixture, with or without any neutral material, of any of the above forms of cannabis or any drink prepared therefrom

The term opium appearing in the definition of narcotic drug is defined under sub-clause (xv) of section 2 of the Act as follows:
opium means:

1. the coagulated juice of the opium poppy; and
2. any mixture, with or without any neutral material, of the coagulated juice of the opium poppy, but does not include any preparation containing not more than 0.2 per cent. of morphine.

The term poppy straw appearing in the definition of narcotic drug is defined under sub-clause (xviii) of section 2 of the Act as follows:
poppy straw means all parts (except the seeds) of the opium poppy after harvesting whether in their original form or cut, crushed or powdered and whether or not juice has been extracted therefrom.

The term manufactured drugs appearing in the definition of narcotic drug is defined under sub-clause (xi) of section 2 of the Act as follows:
manufactured drug means:

1. all coca derivatives, medicinal cannabis, opium derivatives and poppy straw concentrate;
    
2. �any other narcotic substance or preparation which the Central Government may, having regard to the available information as to its nature or to a decision, if any, under any International Convention, by notification in the Official Gazette, declare to be a manufactured drug, but does not include any narcotic substance or preparation which the Central Government may, having regard to the available information as to its nature or to a decision, if any, under any International Convention, by notification in the Official Gazette, declare not to be a manufactured drug.

Thus narcotic drugs are prohibited by the Government and its production, manufacture, sale, consumption, import or export are punishable offences in India.