Drugs and Toxins: Practice Question

A 22 year old male presents with diaphoresis, diarrhea, urination, cough, nasal discharge, vomiting, lacrimation and salivation. He is also noted to be bradycardic and have constricted pupils. Which of the following is most likely correct?
  1. Acetylcholinesterase has been inactivated
  2. The patient overdosed on opiates.
  3. The patient should receive acetylcholinesterase inhibitors as an antidote.
  4. The toxin is causing sympathetic activation.
  5. The toxin is activating alpha and beta adrenergic receptors.
Show Answer and Explanations

Acetylcholinesterase has been inactivated — Correct answer

Correct. The patient has most likely been exposed to organophosphates, which are acetylcholinesterase inhibitors.

The patient overdosed on opiates.

Incorrect. Opiates can cause miosis and bradycardia, but will be more likely to cause constipation, nausea, and no excess diaphoresis, lacrimation, nasal discharge or salivation. The patient has likely been exposed to organophosphates as in insecticides or nerve agents.

The patient should receive acetylcholinesterase inhibitors as an antidote.

Incorrect. Organophosphates are acetylcholinesterase inhibitors. He should receive atropine to block the binding of ACh to cholinergic receptors.

The toxin is causing sympathetic activation.

Incorrect. The toxin is causing parasympathetic activation.

The toxin is activating alpha and beta adrenergic receptors.

Incorrect. Organophosphates inactivate acetylcholinesterase, increasing the levels of acetylcholine, which binds muscarinic and nicotinic cholinergic receptors, activating the sympathetic nervous system.

Summary

Summary: Organophosphates cause parasympathetic activation (rest and digest): diarrhea, urination, cough, nasal discharge, vomiting, lacrimation, bradycardia, miosis. They are acetylcholinesterase inhibitors. Atropine is the antidote.
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