Which term describes an unwanted physical or mental effect caused by a drug?

• A. Side effect
• B. Therapeutic effect
• C. Drug interaction
• D. Tolerance

Answer: (A)

Unwanted effects caused by a drug are called side effects. They are effects other than the intended beneficial (therapeutic) action of the medication and can be physical or mental. Side effects can vary in severity and may appear soon after starting a drug or after a while, and they often depend on the individual and the dose. For example, a cold medication might relieve symptoms but also cause drowsiness—that drowsiness is a side effect.

In contrast, the therapeutic effect is the intended benefit the medicine is meant to produce. A drug interaction refers to how two or more drugs influence each other’s effects, which can change safety or effectiveness. Tolerance means that over time a person may need more of the drug to achieve the same effect, which is a different concept related to dose and response.