Pharmacodynamics · Pharmacology

Non-competitive antagonists decrease the maximal efficacy ($E_{max}$) of an agonist because:

  1. They compete for the same binding site as the agonist
  2. They reduce the number of functional receptors available
  3. They increase the rate of drug metabolism
  4. They decrease the affinity of the agonist for the receptor
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Correct answer: They reduce the number of functional receptors available

Non-competitive antagonists bind either irreversibly to the active site or to an allosteric site. Since the agonist cannot displace them, the total number of available receptors decreases, lowering the maximum possible response regardless of agonist concentration.

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