Sympathomimetics · Pharmacology

Which of the following describes the mechanism of action of 'mixed-acting' sympathomimetics like Ephedrine?

  1. They only block the reuptake of norepinephrine
  2. They directly stimulate adrenergic receptors and release stored norepinephrine
  3. They act exclusively as agonists at alpha-2 receptors
  4. They irreversibly inhibit the enzyme Monoamine Oxidase (MAO) within nerve terminals
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Correct answer: They directly stimulate adrenergic receptors and release stored norepinephrine

Mixed-acting sympathomimetics possess a dual mechanism: they provide direct agonism at alpha and beta receptors while also displacing norepinephrine from storage vesicles in the presynaptic neuron. This results in a prolonged and potent sympathomimetic effect compared to purely direct-acting agents.

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