Which drug is a classic example of a full agonist?

Which drug is a classic example of a full agonist?

• A. Naloxone
• B. Morphine
• C. Buprenorphine
• D. Codeine

Answer: (B)

A full agonist fully activates a receptor, producing the maximum possible response because it has high intrinsic efficacy. Morphine is a classic example at the mu-opioid receptor, yielding full analgesia and the full spectrum of opioid effects at appropriate doses. Naloxone, by contrast, is an antagonist with no intrinsic activity, so it blocks receptor activation rather than activating it. Buprenorphine is a partial agonist; it binds strongly but produces a submaximal response and has a ceiling effect for certain outcomes. Codeine is a relatively weak agonist and acts as a prodrug that must be metabolized to morphine, so its maximal effect is generally lower and variable.

A full agonist fully activates a receptor, producing the maximum possible response because it has high intrinsic efficacy. Morphine is a classic example at the mu-opioid receptor, yielding full analgesia and the full spectrum of opioid effects at appropriate doses. Naloxone, by contrast, is an antagonist with no intrinsic activity, so it blocks receptor activation rather than activating it. Buprenorphine is a partial agonist; it binds strongly but produces a submaximal response and has a ceiling effect for certain outcomes. Codeine is a relatively weak agonist and acts as a prodrug that must be metabolized to morphine, so its maximal effect is generally lower and variable.