The amount of drug required to cause an effect is referred to as:

A) maximal efficacy
B) dose-effect relationship
C) relative potency
D) adverse effect

C) relative potency
The amount of drug required to cause an effect is referred to as relative potency. Note that potency is rarely important overall. A drug with a higher potency requires smaller doses to produce the same effect as a drug with lower potency. The largest effect that a drug can produce is also known as its maximal efficacy, but its potency does not indicate anything about its maximal efficacy.