ABSTRACT
A drug interaction is best defined as ‘‘the possibility that one drug may alter the intensity of pharmacological effects of another drug that is given concurrently.’’ This results in either enhanced activity of the affected drug, which may lead to toxicity, or reduced activity of the affected drug, leading to therapeutic failure. It is also possible that there may be the appearance of a new effect that is not seen with either drug alone, such as caspofungin and cyclosporine coadministration leading to elevated liver function tests. Drug interactions can be divided into either pharmacokinetic (PK) or pharmacodynamic (PD) interactions.
