Determination of the cause -effect relationship of "Undesirable drug reactions": algorithms Naranjo, Karch. Classification of undesirable drug reactions (WHO)

An undesirable drug reaction (UDR) refers to any harmful or unintended effect caused by a medication that occurs at doses typically used for the prevention, diagnosis, or treatment of disease. These reactions can be classified into various categories based on their severity, time of onset, and mechanisms. Determining the cause-effect relationship of UDRs is essential for effective drug safety management, patient care, and regulatory decision-making. This article explores two widely used algorithms for assessing the causality of undesirable drug reactions: the Naranjo and Karch algorithms. Additionally, the WHO classification system for undesirable drug reactions is discussed, highlighting the categories of reactions and their clinical implications. The paper aims to provide comprehensive insight into the assessment, classification, and management of undesirable drug reactions in clinical practice, emphasizing the importance of careful monitoring and patient safety in pharmacotherapy