What is a drug response?

• A. The biochemical or physiological event/change after drug binds to its target receptor
• B. Onset of action
• C. Duration of action
• D. Absorption

Answer: (A)

The effect you’re looking for is the actual biochemical or physiological change that happens after a drug binds to its target receptor. In pharmacology, this is the pharmacodynamic response—the functional outcome produced by receptor activation or inhibition, such as a signaling cascade, ion-channel opening, or enzyme activity change. This is distinct from pharmacokinetic concepts like onset of action (how quickly effects begin), duration of action (how long effects last), or absorption (how the drug enters the body). So the drug response is about the real biological change that follows receptor binding, not just timing or how the drug gets into the system.