What characterizes an idiosyncratic reaction to medication?

An idiosyncratic reaction to medication is characterized by an abnormal response that is unique to an individual. This type of reaction does not follow the typical response patterns expected from a medication, meaning that it can vary greatly from person to person. Such reactions can result from genetic factors, pre-existing conditions, or other individual characteristics that affect how a drug is metabolized or its effects on the body.

In contrast, predictable and common side effects are well-documented responses to medications that are expected in the general population. Mild allergic reactions represent a specific type of response that is often identifiable but not necessarily unique to an individual’s makeup. Side effects that are the same for everyone do not align with the notion of an idiosyncratic reaction, which by definition is distinct and varied from the typical responses seen across a population. Thus, the appropriate answer highlights the individuality of the response to medication.