What is the antidote/reversal agent for dystonic reaction?

• A. Benadryl 25 mg PO
• B. Lorazepam 2 mg IV
• C. Diphenhydramine 50 mg IV/IM/IO
• D. Prochlorperazine

Answer: (C)

Acute dystonic reactions from dopamine-blocking meds are due to an overactive cholinergic system in the brain. The reversal comes from using an anticholinergic agent that also has antihistaminic properties. Diphenhydramine fits that role well because it blocks acetylcholine receptors in the CNS, quickly reducing involuntary muscle contractions typical of dystonia.

The preferred method is giving diphenhydramine by IV or IM (50 mg) because this route provides rapid onset and reliable reversal in an emergency setting. Oral Benadryl is slower and less reliable for a rapid dystonic reaction, so it’s not as effective in acute management. Lorazepam, while it can calm a patient and may help with muscle tension, does not directly counteract the cholinergic-dopaminergic imbalance causing dystonia. Prochlorperazine is a dopamine antagonist that can provoke or worsen dystonia, not treat it.