Classification and mechanism of adverse drug reaction

A response to a drug which is noxious and unintended and which occurs at doses normally used in man for prophylaxis, diagnosis or therapy of disease or for modification of physiological function. (WHO technical report 498, 1972). All noxious and unintended responses to a medicinal product related to any dose should be considered adverse drug reactions. The phrase "responses to medicinal products" means that a causal relationship between a medicinal product and an adverse event is at least a reasonable possibility, i.e. the relationship cannot be ruled out. (ICH E2A, 1995).