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Difficulty: MediumPsychopharmacology and Psychological Therapies

A 34-year-old woman is brought to the emergency department due to a sudden, severe, throbbing headache and blurred vision. Her symptoms began approximately one hour after she ingested an over-the-counter oral decongestant for a viral upper respiratory infection. Her medical history is significant for treatment-resistant atypical depression. After failing several medication trials, she was started on a new psychiatric medication four weeks ago, which has significantly improved her mood. Her temperature is 37.1°C (98.8°F), pulse is 118/min, and blood pressure is 225/125 mmHg. Physical examination reveals a diaphoretic, anxious patient in obvious distress. Neurologic examination demonstrates normal muscle tone, 2+ deep tendon reflexes globally, and absent clonus. Which of the following psychiatric medications was most likely prescribed to this patient?

  1. A
    Fluoxetine
  2. B
    Bupropion
  3. C
    Venlafaxine
  4. PhenelzineAnswer
  5. E
    Amitriptyline

Answer

The correct answer is phenelzine, a monoamine oxidase inhibitor that can cause a hypertensive crisis when combined with sympathomimetic decongestants.
The correct answer is phenelzine. Phenelzine is a monoamine oxidase inhibitor (MAOI) often utilized for treatment-resistant or atypical depression. MAOIs irreversibly inhibit the degradation of monoamines, including norepinephrine. When a patient taking an MAOI is exposed to sympathomimetic medications (such as the pseudoephedrine commonly found in over-the-counter decongestants), the excessive accumulation of norepinephrine provokes a massive systemic sympathetic response. This drug-drug interaction precipitates a severe hypertensive crisis characterized by markedly elevated blood pressure, sudden throbbing headache, diaphoresis, and blurred vision. The absence of hyperthermia and neuromuscular irritability (such as clonus or hyperreflexia) critically distinguishes this crisis from serotonin syndrome.

Step-by-Step Solution

1
Analyze the patient's clinical presentation.
The patient is experiencing a sudden, severe hypertensive crisis (blood pressure 225/125 mmHg, severe headache) with autonomic symptoms but no neuromuscular hyperactivity.
Identifying the specific toxidrome is essential to narrow down the potential drug interactions.
2
Identify the precipitating trigger.
The symptoms began shortly after ingesting an over-the-counter oral decongestant (e.g., pseudoephedrine), which acts as a sympathomimetic agent.
Understanding the mechanism of the trigger helps deduce the underlying vulnerable state caused by the baseline medication.
3
Connect the trigger and presentation to the patient's psychiatric history.
The patient takes a medication for atypical depression. Monoamine oxidase inhibitors (MAOIs) like phenelzine are indicated for atypical depression and can cause a hypertensive crisis when interacting with sympathomimetics.
Synthesizing the interaction between the baseline medication class and the trigger confirms the diagnosis.

Key Concept

Monoamine oxidase inhibitors (MAOIs) can precipitate a life-threatening hypertensive crisis when combined with sympathomimetic agents (such as pseudoephedrine) due to excessive systemic norepinephrine accumulation.
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Topics

Psychopharmacology and Psychological Therapies

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