A patient on tranylcypromine develops a severe throbbing headache with a blood pressure of 220/120 mmHg shortly after a meal containing aged cheese and red wine. The mechanism underlying this hypertensive crisis is:
- A Direct activation of vascular alpha-1 receptors by a metabolite of tyramine
- B Displacement of accumulated norepinephrine from synaptic vesicles by tyramine, an indirectly acting sympathomimetic spared from gut and hepatic degradation ✓
- C Inhibition of neuronal norepinephrine reuptake leading to receptor sensitisation
- D Central disinhibition of sympathetic outflow following serotonin accumulation
Correct answer: B. Displacement of accumulated norepinephrine from synaptic vesicles by tyramine, an indirectly acting sympathomimetic spared from gut and hepatic degradation
Explanation
Tyramine is an indirectly acting sympathomimetic normally degraded by monoamine oxidase in the gut wall and liver. When MAO is inhibited, dietary tyramine reaches the systemic circulation intact, enters noradrenergic terminals via the norepinephrine transporter and displaces stored norepinephrine from vesicles, producing massive adrenergic discharge. It does not act directly on vascular receptors, and the crisis is peripheral rather than centrally mediated.
Reference: Katzung's Basic and Clinical Pharmacology, 15th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.