What is the definition of agonism?

• A. Activating receptors as the drug moves through the body
• B. Blocking receptors to prevent response
• C. Activating enzymes
• D. Neutralizing pathogens

Answer: (A)

Agonism is when a drug binds to a receptor and activates it, producing a cellular response. The effect depends on the drug’s efficacy: a full agonist can trigger the maximum possible response, while a partial agonist causes a smaller effect. This is different from blocking receptors to prevent a response (antagonists) and from actions that don’t involve receptor activation, like activating enzymes or neutralizing pathogens. For example, opioids activate opioid receptors to reduce pain, illustrating how agonism leads to a physiological effect through receptor activation.