Pharmacology is the science of the drugs system. It includes the knowledge of history, source, biochemical and physiological effect, mechanism of action and therapeutic uses of drug. This means, it is related with the interaction of the drug with biological system.The general pharmacology is involves the aspects of sources of drugs, route of administration of drugs, absorption of drugs and factors affecting them, distribution, bio-transformation and excretion. It also involves the mechanism by which drug is acting with receptor, toxicity of drug and preclinical & clinical evaluation.It involves movement of drug. It includes study of absorption, distribution, metabolism and excretion of drugs. The study of what happens to the drug in the body is called as pharmacokinetics.