What best describes potency?

What best describes potency?

• A. The maximum possible effect
• B. The amount of drug needed to achieve a given effect
• C. The duration of action
• D. The half-life

Answer: (B)

Potency is about how much of a drug is needed to produce a given effect. A more potent drug reaches that effect at a smaller dose, while a less potent drug requires a larger dose. It’s all about the dose–response relationship and does not tell you how strong the effect is once you reach it. That latter idea—how strong the effect can be at its maximum—is about efficacy, not potency. The duration of action and half-life describe how long the drug works and how quickly it’s cleared from the body, not how much is needed to get a response. So, the description that best fits potency is the amount of drug required to achieve a specific level of effect.

Potency is about how much of a drug is needed to produce a given effect. A more potent drug reaches that effect at a smaller dose, while a less potent drug requires a larger dose. It’s all about the dose–response relationship and does not tell you how strong the effect is once you reach it. That latter idea—how strong the effect can be at its maximum—is about efficacy, not potency. The duration of action and half-life describe how long the drug works and how quickly it’s cleared from the body, not how much is needed to get a response. So, the description that best fits potency is the amount of drug required to achieve a specific level of effect.