Metabolic basis of drug interactions in the intensive care unit.

Drug interactions are a potentially hazardous consequence of drug therapy, particularly in the critically ill. Many drug interactions result from changes in drug metabolism. These interactions can result in either an increase in toxicity or a decrease in effect. The process of normal drug metabolism depends on the activity of individual metabolizing enzymes. The activity of these enzymes can be altered by many factors, and it is alterations in these enzymes that account for most drug interactions. This article reviews normal and abnormal drug metabolism and discusses how this knowledge can be used to predict and prevent potential drug interactions.