Examkin

Question

Difficulty: EasyPsychopharmacology and Psychological Therapies

An emergency medical team brings a 35-year-old woman to the hospital due to the acute onset of confusion, severe agitation, and muscle twitching. The patient's husband reports that she has a long-standing history of treatment-resistant depression that has been managed with phenelzine for the past year. Four days ago, she consulted a different clinician for persistent low mood and was started on an additional psychiatric medication. Her vital signs show a temperature of 39.4°C (102.9°F), pulse of 124/min, respirations of 20/min, and blood pressure of 165/95 mm Hg. Physical examination reveals profuse diaphoresis, dilated pupils, a bilateral resting tremor, and pronounced hyperreflexia with spontaneous clonus in the lower extremities. The addition of which of the following medications most likely precipitated this patient's current condition?

  1. A
    Bupropion
  2. CitalopramAnswer
  3. C
    Haloperidol
  4. D
    Lithium
  5. E
    Lorazepam

Answer

Citalopram
The correct answer is citalopram. This patient is experiencing serotonin syndrome, a potentially life-threatening condition characterized by the classic triad of altered mental status (confusion, agitation), autonomic instability (hyperthermia, tachycardia, diaphoresis), and neuromuscular hyperactivity (hyperreflexia, spontaneous clonus, tremor). This syndrome is most often precipitated by the concurrent use of two or more highly serotonergic medications. Phenelzine is an irreversible monoamine oxidase inhibitor (MAOI) that prevents the enzymatic breakdown of serotonin. Adding a selective serotonin reuptake inhibitor (SSRI) such as citalopram leads to a massive and rapid accumulation of synaptic serotonin, triggering this dangerous interaction. In clinical practice, MAOIs must be discontinued for at least 14 days before initiating an SSRI (and wait 5 weeks if switching from fluoxetine to an MAOI).

Step-by-Step Solution

1
Identify the clinical syndrome based on the physical examination and vital signs.
The patient exhibits fever, tachycardia, hypertension, altered mental status, diaphoresis, and severe neuromuscular hyperactivity (hyperreflexia and spontaneous clonus), which is the classic triad of Serotonin Syndrome.
Recognizing the distinct neuromuscular signs (clonus/hyperreflexia) helps differentiate Serotonin Syndrome from Neuroleptic Malignant Syndrome (which presents with rigidity).
2
Review the patient's baseline medication list to identify predisposing factors.
The patient takes phenelzine, which is a monoamine oxidase inhibitor (MAOI) that strongly inhibits the breakdown of serotonin in the central nervous system.
MAOIs carry a severe risk of drug-drug interactions, particularly with other serotonergic agents.
3
Determine which newly added psychiatric medication could trigger this syndrome when combined with an MAOI.
Citalopram, a selective serotonin reuptake inhibitor (SSRI), blocks serotonin reuptake. Combining it with an MAOI leads to massive serotonin accumulation.
A minimum 14-day washout period is required when switching between SSRIs and MAOIs to prevent this exact complication.

Key Concept

Serotonin syndrome resulting from the combination of a monoamine oxidase inhibitor (MAOI) and a selective serotonin reuptake inhibitor (SSRI).
Rate this question

Topics

Psychopharmacology and Psychological Therapies

More questions from this topic