Which term describes the strength of a drug's desired effect?

• A. Potency
• B. Efficacy
• C. Safety
• D. Toxicity

Answer: (A)

Potency describes how much of the drug is needed to produce a given level of effect. It’s about the amount or concentration required to achieve a certain response—the more potent, the smaller the dose needed to reach that effect. This is different from efficacy, which is about the maximum effect the drug can produce regardless of dose. So when the question asks about the strength needed to achieve the desired effect, potency is the best fit: it reflects the dose-response strength of the drug. For context, two drugs can have the same efficacy (same maximal effect) but different potencies if one achieves that effect at a lower dose; or one can be more potent yet have a lower maximum effect (lower efficacy).