A 37-year-old man comes to the emergency department due to severe nausea and vomiting a day after receiving chemotherapy for oropharyngeal cancer. He has no other acute symptoms and is otherwise tolerating his treatments. The patient has a history of bipolar disorder that has been stable, as well as a remote history of alcohol abuse. Medications include lithium and lamotrigine. Temperature is 36.7 C (98 F), blood pressure is 140/86 mm Hg, pulse is 98/min, and respirations are 16/min. Physical examination shows mild erythema at the excision site of the primary lesion on the base of the tongue but is otherwise normal. Laboratory results indicate mild dehydration, lithium level of 0.6 mEq/L (normal: 0.6-1.2 mEq/L), and blood alcohol level of 0. The patient is treated with intravenous normal saline and multiple doses of an antiemetic to stop his vomiting. Several hours later, he has sudden neck pain, his neck muscles are stiff, and he has difficulty speaking. Which of the following medications best explains this patient's sudden symptoms?

Question

A 37-year-old man comes to the emergency department due to severe nausea and vomiting a day after receiving chemotherapy for oropharyngeal cancer.  He has no other acute symptoms and is otherwise tolerating his treatments.  The patient has a history of bipolar disorder that has been stable, as well as a remote history of alcohol abuse.  Medications include lithium and lamotrigine.  Temperature is 36.7 C (98 F), blood pressure is 140/86 mm Hg, pulse is 98/min, and respirations are 16/min.  Physical examination shows mild erythema at the excision site of the primary lesion on the base of the tongue but is otherwise normal.  Laboratory results indicate mild dehydration, lithium level of 0.6 mEq/L (normal: 0.6-1.2 mEq/L), and blood alcohol level of 0.  The patient is treated with intravenous normal saline and multiple doses of an antiemetic to stop his vomiting.  Several hours later, he has sudden neck pain, his neck muscles are stiff, and he has difficulty speaking.  Which of the following medications best explains this patient's sudden symptoms?

Quizplus · Accepted Answer

This patient is experiencing an acute dystonia, an extrapyramidal symptom (EPS) that can occur with dopamine antagonists, including antiemetics such as metoclopramide and prochlorperazine, as well as most antipsychotics. Other EPS types include parkinsonism and akathisia, both of which can occur after use of a dopamine antagonist such as metoclopramide. Acute dystonias can develop within hours to days of initiation of a dopamine antagonist. They are characterized by muscle spasms or stiffness in the head and neck, tongue protrusions, torticollis, and oculogyric crisis (ie, forced, sustained elevation of the eyes in an upward position). Laryngeal dystonias can be life-threatening as they may obstruct the airway. Treatment for a dystonic reaction involves discontinuation of the medication and administration of anticholinergic medications (eg, benztropine) or diphenhydramine, and airway protection if necessary. (Choices A, B, and F) Aprepitant, hydroxyzine, and ondansetron also have antiemetic effects, but they are not dopamine antagonists and do not cause an EPS. Aprepitant is a substance P NK1 receptor antagonist. Hydroxyzine is an antihistamine. Ondansetron is a serotonin 5-HT3 antagonist. (Choices C and D) Lamotrigine (an anticonvulsant) and lithium are used in the treatment of bipolar disorder. Neither is typically associated with an EPS. Lamotrigine is associated with Stevens-Johnson syndrome. Lithium toxicity may cause severe vomiting, but this patient's lithium level is low. Educational objective: The antiemetics metoclopramide and prochlorperazine are dopamine antagonists, which, along with most antipsychotics, can cause extrapyramidal symptoms such as acute dystonias, akathisia, and parkinsonism. References: Metoclopramide induced acute dystonic reaction: a case report. (http://www.ncbi.nlm.nih.gov/pubmed/28061898) Movement disorders from the use of metoclopramide and other antiemetics in the treatment of migraine. (http://www.ncbi.nlm.nih.gov/pubmed/26573884)

A 37-Year-Old Man Comes to the Emergency Department Due to Severe