How is the efficacy of a drug defined?

The efficacy of a drug is defined as the degree to which it produces its desired therapeutic response. This concept focuses on the effectiveness of the drug in achieving the intended outcome, such as alleviating symptoms, treating a disease, or improving a condition. Efficacy is a crucial parameter in pharmacology because it helps determine how well a drug works compared to other options and is critical for evaluating its overall therapeutic value.

Understanding efficacy also involves recognizing that a drug can have a high efficacy while still requiring careful consideration of other factors like safety and potential side effects. While the duration of drug effects, the relationship between therapeutic and harmful effects, and the safety margin are all important aspects of pharmacology, they pertain to other characteristics of drugs rather than efficacy specifically.