What is an example of an unpredictable effect caused by medications?

An idiosyncratic reaction is a unique response to a medication that occurs because of an individual's genetic makeup or personal characteristics, rather than the medication's pharmacological action. These reactions are unpredictable and can vary widely between patients, which makes them difficult to anticipate. For instance, one person might experience a severe allergic reaction to a drug that is generally considered safe for the majority of people. This unpredictability underscores the importance of personalized medicine and monitoring for adverse effects, as some individuals may have unexpected and serious responses to medications that would not be anticipated based on standard drug profiles.

In contrast, the expiration date refers to the time until a medication is guaranteed to be effective and does not involve variability in individual responses. Dosage adjustment is a standard practice based on patient-specific factors but is predictable and guided by clinical protocol. A standard procedure outlines consistent steps to be followed in medical practice, which does not encompass the unpredictable nature of an idiosyncratic reaction.