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Difficulty: EasyPsychopharmacology and Psychological Therapies

A 34-year-old man with a history of treatment-resistant depression is brought to the emergency department by his partner. The patient was doing well on a newly prescribed psychiatric medication until this morning, when he took an over-the-counter nasal decongestant for a severe cold. Within an hour of taking the cold medication, he developed a severe, throbbing headache, blurred vision, and neck stiffness. On triage, his temperature is 37.1°C (98.8°F), pulse is 115/min, and blood pressure is 220/125 mm Hg. Physical examination shows diaphoresis and normal deep tendon reflexes without clonus. Which of the following psychiatric medications is this patient most likely taking?

  1. A
    Sertraline
  2. B
    Bupropion
  3. PhenelzineAnswer
  4. D
    Amitriptyline
  5. E
    Trazodone

Answer

Phenelzine
The correct psychiatric medication is an MAOI, such as phenelzine. Monoamine oxidase inhibitors (MAOIs) work by irreversibly inhibiting the enzyme monoamine oxidase, thereby preventing the breakdown of monoamines including serotonin, norepinephrine, and dopamine. When a patient taking an MAOI consumes a sympathomimetic drug, such as pseudoephedrine or phenylephrine found in over-the-counter nasal decongestants, it triggers a massive release or accumulation of catecholamines. This classically precipitates a sudden and potentially life-threatening hypertensive crisis, presenting with markedly elevated blood pressure, severe throbbing headache, diaphoresis, and neck stiffness. The absence of hyperreflexia and clonus helps rule out serotonin syndrome.

Step-by-Step Solution

1
Identify the patient's acute clinical syndrome based on the physical examination and vitals.
The patient is experiencing a sudden, severe hypertensive crisis (blood pressure 220/125 mm Hg) accompanied by a throbbing headache and diaphoresis, without clonus or hyperreflexia.
Establishing the specific toxidrome narrows down the possible pathophysiologic mechanisms.
2
Determine the inciting trigger for the hypertensive crisis.
The symptoms began immediately after taking an over-the-counter nasal decongestant, which contains sympathomimetics like pseudoephedrine or phenylephrine.
Identifying the precipitating agent is necessary to recognize the specific drug-drug interaction.
3
Match the drug interaction with the appropriate class of psychiatric medications.
Monoamine oxidase inhibitors (MAOIs) interact dangerously with sympathomimetics, leading to excessive catecholamines and resulting in a hypertensive crisis.
This confirms which psychiatric drug class causes this classic presentation.

Key Concept

Drug-drug interactions involving Monoamine Oxidase Inhibitors (MAOIs) and sympathomimetics leading to hypertensive crisis.
Estimated Time:1m 0s
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Topics

Psychopharmacology and Psychological Therapies

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