A 31-year-old man, who was hospitalized for substance-induced psychosis two days ago, has had episodic neck stiffness and pain for the past 8 hours. These episodes last for approximately 25 minutes and are accompanied by his neck rotating to the right. During the last episode, he was able to relieve the stiffness by lightly touching his jaw. He has received six doses of haloperidol for auditory hallucinations since his admission. His temperature is 37.3°C (99.1°F), pulse is 108/min, and blood pressure is 128/86 mm Hg. Examination shows a flexed neck rotated to the right. The neck is rigid with limited range of motion. The most likely cause of this patient's symptoms is antagonism of which of the following receptors?

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Quizplus · Accepted Answer

Eductional Objective: Acute extrapyramidal symptoms (eg, dystonia, akathisia, parkinsonism) are due to D2 blockade in the nigrostriatal pathway.  First-generation, high-potency antipsychotics (eg, haloperidol, fluphenazine) strongly block D2 receptors and are most likely to cause extrapyramidal symptoms.

A 31-Year-Old Man, Who Was Hospitalized for Substance-Induced Psychosis Two