Final answer:
Fentanyl is an opioid agonist, binding to opioid receptors and mimicking the effects of endogenous opioids. Naloxone is an opioid antagonist, blocking the effects of opioids like fentanyl and is used to counteract overdoses. The correct matchup is that fentanyl is an agonist, and naloxone is an antagonist.
Step-by-step explanation:
The terms agonist and antagonist refer to how drugs interact with receptors in the body. An agonist is a substance that binds to a receptor and produces a similar effect to the endogenous ligand (the body's natural substance). An antagonist, however, binds to a receptor and produces an opposing effect to the endogenous ligand. In the context of fentanyl and naloxone:
Fentanyl is an agonist because it binds to opioid receptors in the brain and mimics the effects of endogenous opioid peptides, particularly in reducing pain and causing euphoria.
Naloxone is an antagonist because it also binds to opioid receptors but blocks the effects of opioids like fentanyl, and can rapidly precipitate withdrawal in narcotic-dependent individuals or reverse respiratory depression caused by opioid overdose.
Therefore, the correct answer to the question is: c) Fentanyl is an agonist, and naloxone is an antagonist.