[Drug interactions in medical oncology]

Cytotoxic anti-neoplastic drugs are some of the strongest acting drugs. They have a complex pharmacological profile, narrow therapeutic window, steep dose-toxicity curve, and many pharmacokinetic and pharmacodynamic differences both within and between patients. This makes it difficult to avoid adverse effects. These drugs are approved for usage based on their clinical benefit to risk ratio. The recommended dose is usually close to the maximally-tolerated dose in order to achieve maximum therapeutic effect. Therefore, there is more concern about drug interactions affecting the pharmacokinetics of anti-neoplastic drugs than drugs in general. Any physician taking care of oncology patients must understand not only the pharmacokinetic profile(absorption, protein binding, metabolism and excretion)of the anti-neoplastic drugs their using, but also the many factors that affect the pharmacokinetic profile such as hepatic and renal function, and co-administered drugs. Expertise to achieve a good balance between safety and efficacy in medical treatment with proper knowledge in supportive care as well as an understanding of pharmacokinetics, pharmacodynamics and pharmacogenomics is essential for medical oncologists. In this review, we have summarized the drug-drug interactions important for the management of cancer patients. The types of interactions covered are pharmaceutical interactions and interactions at the level of absorption, protein binding, metabolism and excretion.