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Difficulty: Very hardPsychopharmacology and Psychological Therapies

A 45-year-old woman is brought to the emergency department by her husband due to a severe, throbbing headache, blurred vision, and chest palpitations that began 45 minutes ago. She has a 10-year history of major depressive disorder that was poorly responsive to multiple trials of selective serotonin reuptake inhibitors and serotonin-norepinephrine reuptake inhibitors. Six weeks ago, her psychiatrist started her on tranylcypromine. Vital signs are temperature 37.2°C (99.0°F), blood pressure 228/132 mm Hg, pulse 118/min, and respirations 20/min. Physical examination reveals profuse diaphoresis, facial flushing, and pupillary dilation. Neurological examination shows normal muscle tone, 2+ deep tendon reflexes symmetrically, and absent clonus. Mental status examination reveals an anxious woman who is fully oriented to person, place, and time. Her husband mentions they were celebrating their anniversary at a restaurant earlier this evening, where they shared a large platter of aged cheeses and cured meats. Which of the following is the most appropriate initial pharmacological intervention for this patient's current condition?

  1. Intravenous phentolamineAnswer
  2. B
    Oral cyproheptadine
  3. C
    Intravenous esmolol
  4. D
    Intravenous dantrolene
  5. E
    Oral bromocriptine

Answer

The most appropriate initial intervention is intravenous phentolamine.
The correct answer is intravenous phentolamine. This patient is presenting with a tyramine-induced hypertensive crisis, a classic and life-threatening complication of monoamine oxidase inhibitors (MAOIs) such as tranylcypromine. MAOIs irreversibly inhibit monoamine oxidase, the enzyme primarily responsible for breaking down dietary tyramine. When a patient on an MAOI consumes tyramine-rich foods (such as aged cheeses and cured meats), the tyramine enters the systemic circulation and acts as an indirect sympathomimetic. It displaces massive amounts of norepinephrine from presynaptic nerve terminals, leading to severe alpha-1 receptor-mediated vasoconstriction. This presents as a hypertensive emergency, often accompanied by severe headache, palpitations, diaphoresis, and flushing. The physical exam is crucial here: the absence of hyperreflexia, clonus, and lead-pipe rigidity distinguishes this condition from Serotonin Syndrome and Neuroleptic Malignant Syndrome. The most appropriate and life-saving initial treatment is a rapidly acting alpha-adrenergic antagonist, such as phentolamine, to counteract the profound vasoconstriction and lower the blood pressure.

Step-by-Step Solution

1
Analyze the patient's medication history and recent dietary intake.
The patient is taking tranylcypromine, a monoamine oxidase inhibitor (MAOI), and recently consumed aged cheeses and cured meats, which are rich in tyramine.
MAOIs inhibit the breakdown of tyramine in the gastrointestinal tract, leading to systemic tyramine absorption.
2
Evaluate the clinical presentation and physical examination findings.
The patient has extreme hypertension (228/132 mm Hg), sympathetic overactivity (diaphoresis, tachycardia, mydriasis), but normal neurological tone and reflexes without clonus.
These findings precisely match a tyramine-induced hypertensive crisis and rule out Serotonin Syndrome (which features hyperreflexia/clonus) and Neuroleptic Malignant Syndrome (which features severe rigidity).
3
Determine the pathophysiological mechanism of the crisis.
Systemic tyramine acts as an indirect sympathomimetic, displacing massive amounts of norepinephrine from presynaptic vesicles and causing severe alpha-1 mediated vasoconstriction.
Understanding the receptor profile involved dictates the pharmacological antidote.
4
Select the appropriate targeted pharmacological therapy.
Intravenous phentolamine (a short-acting, non-selective alpha-adrenergic antagonist) is selected to immediately reverse the severe alpha-mediated vasoconstriction.
Alpha-blockade is the definitive treatment; beta-blockers must be avoided to prevent unopposed alpha agonism.

Key Concept

Tyramine-induced hypertensive crisis in patients taking MAOIs is caused by massive norepinephrine release and is treated with alpha-adrenergic antagonists like phentolamine.
Estimated Time:1m 30s
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Topics

Psychopharmacology and Psychological Therapies

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