Pharmacology, science of the interaction between chemical substances and living tissues. If the chemical is primarily beneficial, its study falls under the title therapeutics; if primarily harmful, its study is called toxicology. In either case, pharmacodynamics defines how the material is absorbed by the body, where it acts, what its effect is, and how it is metabolized and excreted. See also Drug; Poison.
Pharmacologists determine the therapeutic index of drugs, that is, the relative benefit to toxicity at various doses. This helps define the dosage of a drug that will most benefit a sick person. They also study how various conditions affect the excretion of drugs. For example, many drugs are more slowly metabolized in older persons, so these drugs need to be administered less frequently. Because many chemicals are excreted by the kidney, persons with kidney disease may have impaired drug excretion.
Physicians who specialize in pharmacology are called clinical pharmacologists. Pharmacists who practice in hospitals also specialize in pharmacology, and they can advise physicians on the optimal use of medicinal drugs. See also Medicine.