Which term denotes an unexpected reaction to a medication that is not typical?

The term that denotes an unexpected reaction to a medication that is not typical is idiosyncratic reaction. This type of reaction is characterized by its unpredictability and is not a direct result of the pharmacological action of the drug. Idiosyncratic reactions can vary widely among individuals and may be influenced by genetic factors, underlying health conditions, or interactions with other medications.

In contrast, adverse effects are generally understood as harmful or unpleasant effects that occur as a direct result of a medication's primary actions, while side effects are unintended and typically predictable responses to medication that can occur alongside its desired therapeutic effects. Contraindications refer to specific situations or conditions under which a medication should not be used due to the risk of harm, rather than describing unexpected reactions. Thus, the emphasis on the unexpected nature of the reaction specifically aligns with the definition of idiosyncratic reactions.