A 47-year-old man on tranylcypromine attends a party and eats aged cheese with red wine. Thirty minutes later he develops a throbbing headache, blood pressure of 220/130 mmHg, and palpitations. Which property of tyramine explains this event?

• A It is a directly acting alpha-1 agonist unaffected by metabolism
• B It stimulates adrenal medullary chromaffin cells directly through nicotinic receptors
• C It inhibits neuronal reuptake of norepinephrine, raising synaptic catecholamine concentrations
• D It is normally degraded by intestinal MAO-A, but inhibition allows it to reach sympathetic terminals and displace stored norepinephrine ✓

Explanation

Tyramine in food is normally deaminated by monoamine oxidase A in the gut wall and liver during first-pass metabolism. When MAO is inhibited, dietary tyramine enters the circulation, is taken up into sympathetic nerve endings by NET, and displaces stored norepinephrine from vesicles, producing a massive sympathomimetic surge. Tyramine is an indirectly acting amine, not a direct agonist, and it does not act primarily through reuptake inhibition or nicotinic stimulation.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.