What is Drug?
When a pharmaceutical preparation or naturally occurring substance is used primarily to bring about a change in some existing process or state (Psychological, Physiological or Biochemical) it can be called a Drug.

In Simpler terms any chemical that alters the physical or mental functioning of an individual is a Drug.

Difference between drug use and drug abuse
When drugs are used to cure an illness, prevent a disease or improve the health condition, it is termed “Drug use”.

When drugs are taken for the reason other than medical, in an amount, strength, frequency or manner that damages the physical or mental functioning of an individual, it becomes drug “Abuse.”

Drug abuse of medical drugs
Drugs with medical use can be abused in the following ways.
Too much
Taking an increased doses without medical advice.
Too often
Taking small doses frequently
Too long
Taking an drug for an extended period of time – longer than the prescribed period.

Wrong use
Taking a drug for reason other than medical, for which it is intended or taking a drug without medical advice. Wrong combination

Taking a drug in combination with certain other drugs.

Illegal drugs like Brown–Sugar and opium have no medical use at all, With these drugs there is no drug use, to use them is to abuse them.

Drug abuse and drug addiction

• Tolerance
• Psychological dependence
• Physical dependence
• Withdrawal symptoms

Classification of addictive drugs
Addictive drugs can be classified into five major categories according to their effects on the user.

• Narcotic analgesics
• Stimulants
• Depressants
• Hallucinogens
• Cannabis

Narcotic Analgesics

• In Greek prefix ‘Narco’ means to ‘Deaden’ or ‘benumb’.
• Analgesics means pain killer or pain relieving.
• The term Narcotic medically refers to opium and opium derivatives or synthetic substitutes that produce opium–like effects.

Drugs belonging to this category can be studied under three broad categories