This patient with bradycardia, miosis, and excessive secretions (eg, diaphoresis, rhonchi, drooling) has evidence of cholinergic toxicity, likely due to accidental or intentional exposure to an organophosphate pesticide.  Organophosphates inhibit acetylcholinesterase, leading to hyperstimulation of the muscarinic (mnemonic: DUMBELS—see table) and nicotinic (ie, muscle fasciculations, weakness, paralysis) cholinergic receptors.

Management of organophosphate toxicity includes stabilization (ie, airway, breathing, circulation), decontamination to prevent continued exposure (ie, removal of soiled clothes, irrigation of skin), and reversal of cholinergic hyperstimulation.  Atropine, a competitive inhibitor of acetylcholine at the muscarinic receptor, should be given immediately and leads to resolution of muscarinic symptoms (eg, bronchospasm).  Because atropine does not act on the nicotinic receptors, patients with evidence of neuromuscular dysfunction should then receive pralidoxime, a cholinesterase-reactivating agent that can relieve both the muscarinic and nicotinic effects.

(Choice B)  Buprenorphine is a partial agonist of the mu-opioid receptor and is used to suppress withdrawal in opioid use disorder.  It would worsen this patient's somnolence.

(Choice C)  Epinephrine is an adrenergic receptor agonist used to treat anaphylaxis, a type I hypersensitivity response to an allergen (eg, insect sting).  Although airway edema often results in wheezing, anaphylaxis usually also presents with skin or mucosal manifestations (eg, tongue swelling, rash) and tachycardia, not bradycardia.  Miosis is unexpected.

(Choice D)  Hemodialysis, in addition to fomepizole, is indicated for toxic alcohol (ie, methanol, ethylene glycol) ingestion.  However, this condition usually presents with altered mental status and vision changes (in methanol) or flank pain and hematuria (in ethylene glycol).  Hemodialysis is not indicated in cholinergic toxicity.

(Choice E)  Naloxone is a opioid receptor antagonist used to treat opioid overdose, which can cause pinpoint pupils and sedation but would not be expected to cause hypersalivation, wheezing, or diaphoresis.

Educational objective:
Organophosphates are acetylcholinesterase inhibitors that are commonly used as agricultural pesticides.  Toxicity is characterized by signs of cholinergic excess (eg, miosis, bronchospasm, muscle fasciculations/weakness, diarrhea, vomiting, lacrimation).  First-line therapy is atropine, a competitive inhibitor of acetylcholine at the muscarinic receptor.