Which term describes an individual's overreaction to medication?

The term that describes an individual's overreaction to medication is hypersensitivity. This condition occurs when the immune system reacts excessively to a medication, leading to an exaggerated response that can range from mild allergic reactions, such as rashes, to severe responses, including anaphylaxis. Hypersensitivity is specific to an individual's unique response to a substance and can vary significantly from person to person.

Other terms, while relevant to medication responses, describe different phenomena. An adverse reaction generally refers to any harmful or unintended response to a medication, which may not necessarily be an overreaction. An idiosyncratic response is a type of adverse reaction that occurs due to a unique sensitivity to a drug that is not related to the drug’s pharmacological action. The synergistic effect describes the interaction of two or more medications that results in a greater effect than would be expected from their individual effects alone, rather than an overreaction of an individual to a single medication.