Drug tolerance is an condition which develops due to prolong use of an drug. In this condition body becomes used to medicine and current dose will not be effective and there is need to increase the dose. Drug withdrawal refers to specific sign and symptoms which develop when a drug which cause physical dependence is discontinued suddenly after a long use. Drug use means use of any drug as medicine to treat an illness in recommended doses prescribed by doctor for specific periods of time.Drug abuse refers to misuse of the drug not to treat an illness but for recreational or enjoyment purpose. Drug dependence is condition in which body become dependent of any narcotic drug and needs its addicted levels every time in blood due to prolong use either for recreational purpose or prescribed by the doctor.