Review Question - QID 101708

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Muscarinic Antagonists Atropine Toxicity QID: 101708 (M1.PH.14.44)

QID 101708 (Type "101708" in App Search)

A 5-year-old boy is brought to the ED with fever and altered mental status. The boy was in his normal state of health until a few hours ago when he began to "not feel good" while on a deep-sea fishing trip as part of his family vacation. By the time that the family made it back to shore, the boy was experiencing blurred vision and confusion. In the ED his vitals were 101.6F, HR160, RR18, and O2 99% on room air. On exam, his skin is dry and flushed, and his abdomen is covered in small, round, stickers similar to that in Figure A. What gastrointestinal and urinary symptoms would you expect in this patient?

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Incontinence of stool; urine retention

27/450

Incontinence of stool and urine

11%

49/450

Constipation; urine retention

65%

293/450

Constipation; incontinence of urine

10%

43/450

Incontinence of stool; no urinary symptoms

17/450

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Fever, blurred vision, confusion, and flushed skin in a patient with transdermal patches on his skin following a boat ride is suggestive of scopolamine overdose. Other anti-muscarinic effects include retention of urine and constipation.

Scopolamine is a quick-acting muscarinic antagonist delivered via transdermal patch commonly used for motion sickness and post-operative nausea. Like atropine, scopolamine crosses the blood-brain barrier, and thus it has similar symptoms of overdose: increased body temperature, tachycardia, dry-mouth, flushed skin, cycloplegia, confusion, constipation, and urine retention. Treatment is supportive and with pheostigmine, an acetylcholinesterase inhibitor that can also cross the blood-brain barrier and acts by increasing the concentration of acetylcholine in the synaptic cleft.

Frithsen et al. discuss the approach to medication overdose in the primary care setting. Activated charcoal can be used up to one hour after ingestion in the case of most oral medications while further management is being arranged (Recommendation C). Other ingestions that can have a similar presentation to that scopolamine overdose include: antihistamines, atropine, psychoactive drugs, and tricyclic antidepressants.

Corallo et al. discuss a case report of unintentional scopolamine overdose in an adult after ingesting 60-80mg of scopolamine hydrobromide oral tablets (recommended dose: 0.3-0.6mg). This patient presented with disorientation and agitation. He was not tachycardic or febrile at the time of presentation, but exhibited warm, dry skin, dilated pupils, and repeated myoclonic spams. He was managed supportively with sedation and intubation and was discharged without any long term effects.

Figure A shows a scopolamine transdermal patch used as generally directed.

Incorrect Answers:
Answers 1,2,4,5: An overdose of scopolamine will inhibit parasympathetic innervation of the gut and bladder, resulting in constipation and urine retention, respectively.