Review Question - QID 109380

This patient is presenting with fever, flushing, altered mental status, dry mouth, and mydriasis with increased exposure to an anticholinergic (e.g., ipratropium and diphenhydramine), suggesting the diagnosis of antichoinergic toxicity, which should be treated with physostigmine.

Anticholinergic toxicity can result from an overdose of a variety of medications, such as antihistamines, antimuscarinics (including inhaled agents and ophthalmic drops), scopolamine, tricyclic antidepressants (TCAs), anti-Parkinsons, and antipsychotics. Clinical features of anticholinergic intoxication include flushing, anhidrosis, blurred vision, hyperthermia, non-reactive mydriasis, alterations in mental status, delirium, hallucinations, constipation, urinary retention, urticaria, and tachycardia. The diagnosis of anticholinergic toxicity is based on these clinical findings and on the results of a trial of physostigmine, which is the initial management following stabilization of airway, breathing and circulation.

Figure A is an EKG demonstrating sinus tachycardia.

Incorrect Answers:
Answer 1: Activated charcoal can be used for gastrointestinal decontamination if an oral agent caused her toxicity, and if she presented within two hours of ingestion. In this case, her presentation is likely due to the overtreatment of her seasonal allergies with intranasal anticholinergic plus an antihistamine.

Answer 2: Atropine is a muscarinic antagonist that would worsen that patient’s anticholinergic toxicity symptoms. Atropine is instead used to block the effects of cholinesterase inhibitors, such as organophosphates. A cholinergic toxidrome would present with diarrhea, urination, miosis, bronchospasm, bradycardia, emesis, lacrimation, sweating, and salivation.

Answer 4: Pyridostigmine is an acetylcholinesterase inhibitor like physostigmine. However, unlike physostigmine, which is a tertiary amine, pyridostigmine is a quaternary amine, therefore it lacks the central antimuscarinic activity needed to make it an effective antidote. Pyridostigmine is used to treat myasthenia gravis.

Answer 5: Sodium bicarbonate should be given to protect against cardiotoxicity in TCA overdose. While this patient could have anticholinergic side effects from TCAs, her EKG does not show QRS prolongation or a ventricular arrhythmia, which would be indications for sodium bicarbonate. Other signs of TCA toxicity would be hypotension, convulsions, coma, and respiratory depression.

Bullet Summary:
Anticholinergic toxicity will present with a syndrome of anhidrosis, blurred vision, hyperthermia, constipation, urinary retention, and altered mental status, and it should be treated with physostigmine.