A 38-year-old woman is brought to the emergency department by her sister after developing acute anxiety, headache, nausea, and vomiting while eating dinner. The patient has no history of migraine, hypertension, or diabetes. She has no known food allergies but does have a history of seasonal allergies treated with diphenhydramine. The patient has a long history of major depressive disorder and panic attacks and has had poor response to several antidepressants. For the past year, she has been treated with escitalopram, which she discontinued a week ago. Yesterday, she started taking phenelzine for depressive symptoms. On arrival, the patient is agitated, disoriented, diaphoretic, and tremulous. Temperature is 38.9 C (102 F), blood pressure is 170/110 mm Hg, pulse is 115/min, and respirations are 24/min. Physical examination shows dilated pupils and bilateral tremors. Deep tendon reflexes are 3+ bilaterally. Which of the following is the most likely cause of these findings in this patient?

Question

A 38-year-old woman is brought to the emergency department by her sister after developing acute anxiety, headache, nausea, and vomiting while eating dinner.  The patient has no history of migraine, hypertension, or diabetes.  She has no known food allergies but does have a history of seasonal allergies treated with diphenhydramine.  The patient has a long history of major depressive disorder and panic attacks and has had poor response to several antidepressants.  For the past year, she has been treated with escitalopram, which she discontinued a week ago.  Yesterday, she started taking phenelzine for depressive symptoms.  On arrival, the patient is agitated, disoriented, diaphoretic, and tremulous.  Temperature is 38.9 C (102 F), blood pressure is 170/110 mm Hg, pulse is 115/min, and respirations are 24/min.  Physical examination shows dilated pupils and bilateral tremors.  Deep tendon reflexes are 3+ bilaterally.  Which of the following is the most likely cause of these findings in this patient?

Quizplus · Accepted Answer

11ec25c8_d801_dbde_bc81_dfed1d7114ea_MD0003_00 This patient is taking phenelzine, a monoamine oxidase inhibitor (MAOI) used in treatment-resistant depression. MAOIs irreversibly inhibit monoamine oxidase, preventing the oxidative deamination of serotonin, norepinephrine, and dopamine. Her acute symptoms (agitated delirium, diaphoresis, hyperthermia, hypertension, tachycardia, dilated pupils, vomiting, tremor, and hyperreflexia) are consistent with serotonin syndrome, most likely due to a drug-drug interaction between phenelzine and escitalopram, the selective serotonin reuptake inhibitor (SSRI) that she discontinued a week ago. Serotonin syndrome is caused by excess serotonin levels and is characterized by a triad of mental status changes, autonomic dysregulation, and neuromuscular hyperactivity. Serotonin syndrome Most antidepressants should be discontinued 2 weeks before beginning an MAOI to avoid serotonin syndrome. The SSRI fluoxetine is an exception due to its long half-life and must be stopped 5 weeks before initiating an MAOI. (Choice A) Anticholinergic toxicity is characterized by hyperthermia, delirium, dilated pupils, dry mucous membranes, urinary retention, and decreased bowel sounds. It would not cause diaphoresis, hyperreflexia, and tremors, as seen in this patient. (Choice B) Malignant hyperthermia presents with hyperthermia, tachycardia, rigidity, and rhabdomyolysis following the administration of succinylcholine or a volatile inhaled anesthetic (eg, halothane, sevoflurane). (Choice C) Neuroleptic malignant syndrome is characterized by hyperactive vital signs (eg, hyperthermia, tachycardia), altered mental status, and rigidity that develops in the context of antipsychotic use. The absence of an inciting medication, this patient's hyperreflexia, and the overall clinical picture make serotonin syndrome more likely. (Choice D) Abrupt discontinuation of short-half-life antidepressants can cause dizziness, fatigue, headache, nausea, anxiety, myalgia, and paresthesia. However, it would not cause agitated delirium, hyperthermia, hypertension, and hyperreflexia, which are more consistent with serotonin syndrome. (Choice F) A hypertensive crisis may occur in patients who consume foods rich in the sympathomimetic substance tyramine while taking an MAOI. Prohibited foods include aged cheeses and aged, smoked, pickled, or cured meats/fish/poultry. Although this patient's meal may have contained tyramine, her dilated pupils, hyperreflexia, and hyperthermia are consistent with serotonin syndrome and not an MAOI-associated hypertensive crisis. Educational objective: Switching antidepressants to or from a monoamine oxidase inhibitor (MAOI) must be done cautiously as drug-drug interactions can cause serotonin syndrome. Switching from most antidepressants to an MAOI requires a 2-week washout. References: Dietary restrictions and drug interactions with monoamine oxidase inhibitors: an update. (http://www.ncbi.nlm.nih.gov/pubmed/22951238) Serotonin syndrome. (http://www.ncbi.nlm.nih.gov/pubmed/24358002) Serotonin syndrome: preventing, recognizing, and treating it. (http://www.ncbi.nlm.nih.gov/pubmed/27824534)

A 38-Year-Old Woman Is Brought to the Emergency Department by Her