Drug interactions in surgical patients

Abstract

Drug interactions, defined as when the administration of a single substance (drug, nutrient, or tobacco) modifies the response to a drug, occur relatively frequently in surgical patients and may result in increased morbidity and lengthened hospital stay. Drug interactions also account for some instances of drug ineffectiveness or exaggerated pharmacologic response. There are many types of drug interactions. However, most of them are related to altered drug pharmacokinetic properties, where there are alterations in drug absorption, distribution, metabolism, or elimination; or altered drug pharmacodynamic actions, where two agents may have synergistic, additive, or antagonistic pharmacologic effects. The term, drug interaction, usually refers to pairs of drug substances administered concurrently, but more than two agents may be involved. When patients are taking a large number of different medications, there may be multiple drug interactions with additive or antagonistic effects, the overall effects of which are difficult to predict. There are hundreds of reported drug interactions, and some may be of important clinical consequence. In surgical patients, the majority of drug interactions involve histamine-2 blockers (particularly cimetidine), digoxin, warfarin, or a variety of agents that may be administered during anesthesia. Recognition of the potential for adverse drug interactions is of primary importance in minimizing their effects. Usually, potentially interacting drugs may be administered concurrently as long as appropriate patient or laboratory assessments are performed. For some agents, such as digoxin or theophylline, serum drug concentrations may aid in the avoidance of adverse drug interactions.