Which statement best describes potency in pharmacology?

Which statement best describes potency in pharmacology?

• A. The maximum achievable effect
• B. The duration of action
• C. The amount of drug needed to produce a given effect
• D. The time to onset

Answer: (C)

Potency describes how much of a drug is needed to produce a given level of effect. In other words, it’s about the dose-response relationship: a more potent drug reaches the same effect at a smaller dose. This is different from efficacy, which is about the maximum effect a drug can produce, regardless of dose. Potency also isn’t about how long the drug acts (duration) or how quickly it starts (time to onset); those relate to pharmacokinetics and other pharmacodynamic factors. For example, if one drug achieves 50% of its maximum effect at a much lower dose than another drug, the first is more potent. So the statement that best describes potency is the amount of drug required to produce a given effect.

Potency describes how much of a drug is needed to produce a given level of effect. In other words, it’s about the dose-response relationship: a more potent drug reaches the same effect at a smaller dose. This is different from efficacy, which is about the maximum effect a drug can produce, regardless of dose. Potency also isn’t about how long the drug acts (duration) or how quickly it starts (time to onset); those relate to pharmacokinetics and other pharmacodynamic factors.

For example, if one drug achieves 50% of its maximum effect at a much lower dose than another drug, the first is more potent. So the statement that best describes potency is the amount of drug required to produce a given effect.