1 Analysis of drug interactions

Drug combinations are of increasing importance in modern medicine, and particularly in anaesthesia where drugs are given acutely and usually intravenously. Anaesthesia involves the co-administration of several drugs, with a variety of pharmacological effects and different modes of action. When drugs are given in combination there is the possibility that they may interact to either enhance or antagonize each other's effects. It is important, therefore, that the nature of potential drug interactions be properly analysed and quantified. The analysis of drug interactions has a long history, and many different approaches have been tried. One of the most commonly used methods is isobolographic analysis, and the closely related technique of fractional analysis. Other methods that have been used to study interactions related to anaesthesia are those based on logistic regression and parallel line assays. The advantages and disadvantages of these methods are discussed.