Mirtazapine relieves depression through a mechanism distinct from SSRIs and SNRIs. Its principal pharmacological actions are:
- A Alpha-2 autoreceptor antagonism with 5-HT2 and 5-HT3 receptor blockade ✓
- B Selective inhibition of monoamine oxidase type A
- C Potent D2 and D3 receptor antagonism with 5-HT1A agonism
- D Inhibition of vesicular monoamine transporter 2
Correct answer: A. Alpha-2 autoreceptor antagonism with 5-HT2 and 5-HT3 receptor blockade
Explanation
Mirtazapine blocks presynaptic alpha-2 adrenergic autoreceptors, disinhibiting noradrenaline and serotonin release, and simultaneously blocks 5-HT2 and 5-HT3 receptors, so serotonin transmission is directed toward the 5-HT1A receptor. This profile produces sedation via H1 blockade and appetite stimulation with weight gain, useful in depressed patients with insomnia and poor intake. It does not inhibit MAO or affect dopamine receptors significantly.
Reference: Katzung's Basic and Clinical Pharmacology, 15th ed.
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