Pharmacodynamics and pharmacokinetics in the elderly.

The paper deals with changes in pharmacodynamics (the study of what the drug does to the body) and pharmacokinetics (the study of what the body does to the drug) in the elderly. Elderly population takes 25–30 per cent of drugs taken by total population. In the elderly pharmacodynamics and pharmacokinetics are altered. According to pharmacokinetics, gastric juice pH is elevated which influences drug solubility and absorption. Drug distribution is decreased in the elderly because of decreased cardiac output, increased peripheral vascular resistance, diminished blood flow in the liver and the kidneys, reduced total amount of water in the body. Drug metabolism and biotransformation mainly take place in the liver and is reduced very often. Drug elimination is reduced very often because of reduced renal reserve: creatinine clearance is reduced in the elderly in spite of the fact that the serum values remaining in the normal range. Pharmacodynamics could be altered in the elderly, as a consequences of receptor binding, of postreceptor effects, and of chemical interactions. The clinical effects of drug concentrations could be greater or smaller than those in middle-aged or younger persons.