What is defined as an adverse effect in medication?

An adverse effect in medication refers to any harmful or unintended response to a medication. This includes reactions that occur after the patient has been exposed to a drug previously and may develop hypersensitivities or allergies upon re-exposure. Such responses can vary in severity and impact patient safety. That's why options regarding general side effects, medication interactions, and beneficial effects do not accurately capture the specific characteristics that define an adverse effect. The focus of an adverse effect is on the negative consequences that can arise from the administration of a medication, particularly those that involve the patient's immune response upon subsequent exposure to the drug.