Pharmacodynamics · Pharmacology

Which of the following is an example of 'Functional Antagonism'?

  1. Atropine blocking acetylcholine at cardiac muscarinic receptors
  2. Epinephrine reversing histamine-induced bronchoconstriction
  3. Protamine neutralizing heparin through chemical bonding
  4. Ketoconazole inhibiting the metabolism of cyclosporine
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Correct answer: Epinephrine reversing histamine-induced bronchoconstriction

Functional (or physiological) antagonism occurs when two agonists act on completely different receptors to produce opposing physiological effects. Epinephrine causes bronchodilation via $\beta_2$ receptors, which counteracts the bronchoconstriction caused by histamine at $H_1$ receptors.

Difficulty: Medium Question 10 of 20

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