Which factor indicates that the less amount needed conveys more potency of a drug?

The concept of potency relates directly to the amount of a drug that is needed to produce a specific effect. A drug that requires a smaller dose to achieve the same effect is considered to be more potent than one that requires a larger dose. Thus, when it is stated that "the less amount needed conveys more potency of a drug," it is precisely the definition of potency being referenced.

This is distinct from efficacy, which refers to the maximum effect a drug can produce regardless of the dose, and effectiveness, which reflects how well a drug works in real-world settings. The therapeutic index, on the other hand, is a measure of the safety of a drug, indicating the range between effective and toxic doses. Therefore, potency is the most relevant factor indicating that a smaller amount of a drug is required to achieve a desired effect.