Review Question - QID 103782

The patient in this vignette experienced a side effect to a typical antipsychotic medication 2 hours after administration. She most likely experienced an acute dystonic reaction, which can be treated with an anticholinergic (e.g. benztropine) or diphenhydramine, an antihistamine with anticholinergic properties.

High potency antipsychotics, such as haloperidol, cause lower rates of anticholinergic side effects than low potency antipsychotics, but cause higher rates of extrapyramidal symptoms (EPS). Examples of EPS include acute dystonia, Parkinsonism, akathisia, and tardive dyskinesia. Torticollis refers to dystonia (sustained, involuntary muscle contraction) affecting the neck. Patients often complain that their neck is "stuck" turned to one side and they are unable to return their head to a neutral position. While torticollis is a common presentation of acute dystonia related to antipsychotic use, any muscle group can be affected. These symptoms occur due to disruption of normal dopaminergic signaling in the basal ganglia pathways that modulate movement.

Lewis et. al review the clinical manifestations, diagnosis and management of acute dystonic reaction. They note that symptoms often develop within hours to days of antipsychotic medication initiation. They discuss management with diphenhydramine as well as other adjunctive therapies.

Illustration A shows a woman with an acute dystonic reaction presenting as torticollis.

Incorrect Answers:
Answer 1: Bradykinesia may be a manifestation of Parkinsonism that develops secondary to antipsychotic use. However, it typically presents several days after administration. Of note, it is also treated with anticholinergic medications.

Answer 2: Constant urge to move, also known as akathisia, is a known side effect of antipsychotic use but is treated with benzodiazepines or beta-blockers.

Answer 3: Fever is often present in patients that develop neuroleptic malignant syndrome (NMS), a rare but life-threatening reaction secondary to antipsychotic medication use. However, it is treated with dantrolene and is not managed with diphenhydramine.

Answer 4: Involuntary and repetitive movements of the tongue may be a manifestation of tardive dyskinesia (TD). TD develops after months to years of antipsychotic medication use. However, TD is managed with VMAT-2 inhibitors such as valbenazine, not diphenhydramine.

Bullet summary:
Typical antipsychotic medications are associated with extrapyramidal symptoms such as dystonia or torticollis, which are managed with diphenhydramine.