Which term describes a harmful reaction that occurs at normal doses of medication?

The correct term that describes a harmful reaction occurring at normal doses of medication is an adverse drug reaction. This term specifically refers to any noxious, unintended, and undesired effect of a drug that occurs at doses normally used in humans for prophylaxis, diagnosis, or therapy. Adverse drug reactions can manifest in various ways, ranging from mild symptoms to severe health complications, and are significant considerations in pharmacology and patient care.

In contrast, side effects are generally predictable and can be either harmful or beneficial, occurring alongside the therapeutic effect of the medication but are not always harmful in nature. The therapeutic effect refers to the desired and intended effect of the medication, which helps in treating or alleviating symptoms of a disease. An allergy is a specific and often immune-mediated reaction to a medication that can occur upon first exposure or after repeated exposures, but it is not solely defined by the dosage at which it occurs, as it can involve hypersensitivity that may not align with the concept of normal dosing.