A 32-year-old man on phenelzine for atypical depression attends a party where he consumes red wine and aged cheese. He develops a severe throbbing headache, blood pressure of 220/120 mmHg, and palpitations. The substance responsible for this crisis produces its pressor effect primarily by:

• A Direct stimulation of vascular alpha-1 receptors
• B Stimulating adrenal medullary release of catecholamines through nicotinic receptors
• C Blocking reuptake of norepinephrine into nerve terminals
• D Displacing stored norepinephrine from sympathetic nerve terminals ✓

Explanation

Tyramine is an indirectly acting sympathomimetic taken up by NET into noradrenergic terminals, where it displaces stored norepinephrine from vesicles into the synaptic cleft. MAO-A normally degrades dietary tyramine in the gut wall and liver; phenelzine inhibits this, allowing large amounts to reach the circulation. Direct receptor stimulation and uptake blockade are properties of other agents such as phenylephrine and cocaine respectively.

Reference: Katzung Basic and Clinical Pharmacology, 15th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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