The effect of rifampin on theophylline pharmacokinetic parameters (following intravenous aminophylline) in normal volunteers

Many drug interactions are discovered serendipitously. However, it is possible to predict the potential for ann interaction between two drugs based on the physical, chemical, pharmacokinetic, and pharmacological properties of those drugs. The effect of such an interaction on the patient is dependent on many factors, including the nature and magnitude of the interaction, and is therefore difficult to predict. A potential interaction would best be studied in a controlled experimental setting to limit the interference of variable and to protect the subjects. A potential interaction may exist between rifampin and theophylline. Rifampin has been shown to induce microsomal enzymes and to alter the clearance of many drugs. Theophylline is metabolized by microsomal enzymes and has demonstrated an increase in clearance following conditions that increase microsomal activity. To date, the interaction between these two drugs in humans has not been described, but a recent study demonstrated no interaction between these two dugs in rabbits. However, since the effect of rifampin on drug clearance has shown interspecies variation, an interaction between rifampin and theophylline may exist in humans.