Gastrointestinal drugs in the elderly.

The pharmacokinetic changes that occur not infrequently when a single drug is taken by an elderly individual are usually not clinically important because of the wide therapeutic index between pharmacological and toxic effects. On the other hand, when multiple medications are administered simultaneously, additive effects may be seen. This concept is extended further in the presence of impaired function of an excretory or of a metabolic organ, such as with renal disease or cirrhosis of the liver. Thus when an agent whose pharmacological half-life is prolonged in the elderly is administered to an older person with cirrhosis of the liver and/or renal disease, the dose must be reduced considerably in order to avoid excessively elevated blood levels and the concomitant side effects. In contrast, in the absence of liver and/or renal disease, no toxic side effect might be expected. When multiple drugs are given, which may interact with each other, the potential for drug reaction is greatly increased. The physician's recognition of these basic pharmacological changes in the elderly should greatly reduce such drug reactions.