What term describes a harmful side effect from a medication?

• A. Adverse Effect
• B. Antagonism
• C. Bolus
• D. Contraindications

Answer: (A)

An adverse effect is a harmful or undesired response that occurs with normal drug dosages. This term specifically captures reactions that are detrimental to the patient, ranging from mild nausea to life‑threatening events like anaphylaxis or liver injury. It differentiates harmful outcomes from routine, minor side effects that patients can tolerate. Antagonism describes a drug interaction where one medication blocks another’s effect, not a reaction to a drug itself. A bolus is simply a rapid dose given all at once, not a description of a side effect. Contraindications are conditions or situations where a drug should not be used because the risk outweighs benefit, not a reaction after administration.