Drug : Drug may be defined as an agent for use in diagnosis, mitigation, treatment, cure or prevention of disease in human beings or animals.When administered orally, applied topically, inserted in to body cavity or injected in body, these agent either repair a body organ its function to normal condition. Drugs are obtained from the following sources :-       1)Natural Sources -                                                                                                                           Plants                         :  ATROPINE, RESERPINE, MORPHINE etc. Animal                       :   INSULIN, VACCINES, ENZYMES etc. Minerals                     :  KAOLIN, LIQUID PARAFFIN etc. Micro-organism         :  Antibiotics etc.       2)Semi-synthetic drugs   :    ANTIBIOTICS,MORPHINE DERIVATIVES etc.       3)Synthetic Drugs           :   A SPIRIN, PARACETAMOL, PRO-DRUGS such as                                                                                OMEPRA