Drugs may be obtained from different sources like plant, animal, minerals, microorganism, synthetic, semi synthetics. There is a vast vegetative flora from which leaves, flowers, fruits, roots, stems, etc. are being used as drugs. Liver, endocrine glands and secretory organs of animals are used to extract active drugs. The substance isolated from microorganism are used in high dilution to kill or prevent growth of other microbes. Synthetics are drugs that are synthesized by chemical process.