Modern medicine uses thousands of different types of drugs, which come from a variety of sources. They can be broadly divided into those that are derived from natural sources such as plants and herbs, and those that are produced artificially from chemicals. A recent development involves genetically engineering certain bacteria to produce a drug for a specific purpose.
Drug, any chemical substance that affects the functioning of living things and the organisms (such as bacteria, fungi, and viruses) that infect them. Pharmacology, the science of drugs, deals with all aspects of drugs in medicine, including their mechanism of action, physical and chemical properties, metabolism, therapeutics, and toxicity. This article focuses on the principles of drug action and includes an overview of the different types of drugs that are used in the treatment and prevention of human dieses. For a discussion of the nonmedical use of drugs, see drug use.
Until the mid-19th century the approach to drug therapeutics was entirely empirical. This thinking changed when the mechanism of drug action began to be analyzed in physiological terms and when some of the first chemical analyses of naturally occurring drugs were performed. The end of the 19th century signaled the growth of the pharmaceutical industry and the production of the first synthetic drugs. Chemical synthesis has become the most important source of therapeutic drugs. A number of therapeutic proteins, including certain antibodies, have been developed through genetic engineering.
Drugs produce harmful as well as beneficial effects, and decisions about when and how to use them therapeutically always involve the balancing of benefits and risks. Drugs approved for human use are divided into those available only with a prescription and those that can be bought freely over the counter. The availability of drugs for medical use is regulated by law.
Drug treatment is the most frequently used type of therapeutic intervention in medicine. Its power and versatility derive from the fact that the human body relies extensively on chemical communication systems to achieve integrated function between billions of separate cells. The body is therefore highly susceptible to the calculated chemical subversion of parts of this communication network that occurs when drugs are administered.
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