Drug design, also known as rational drug design, is the inventive process of finding new medications based on the knowledge of a biological target. Drug design defines the design of molecules that are complementary in shape and charge to the bimolecular target with which they interact and therefore will bind to it. Drug development is the process of bringing a new pharmaceutical drug to the market once a lead compound has been identified through the process of drug discovery. Drug design is an integrated developing discipline which portends an era of ‘tailored drug’. It involves the study of effects of biologically active compounds on the basis of molecular interactions in terms of molecular structure or its physico-chemical properties involved. It studies the processes by which the drug produce their effects, how they react with the protoplasm to elicit a particular pharmacological effect or response how they are modified or detoxified, metabolized or eliminated by the organism.