Review Question - QID 216502

This patient who presents with diarrhea, emesis, salivation, and bronchospasm was most likely poisoned with organophosphate fertilizers from the overturned truck. Hyoscyamine is a medication that is primarily used as a gut antispasmodic that also has anticholinergic properties.

The cholinergic toxidrome involves the overactivation of both muscarinic and nicotinic acetylcholine receptors. A common cause of this toxidrome is poisoning with organophosphate fertilizers either through work as a farmer or due to industrial or transportation accidents. The first-line treatment for cholinergic poisoning is atropine, which is a nonselective muscarinic acetylcholine receptor inhibitor. Patients with organophosphate poisoning should also be treated with pralidoxime, which functions by displacing the organophosphate from the acetylcholine receptor and regenerating the underlying enzyme; however, administration of this drug is very time-sensitive. In rare circumstances when these first-line medications are not available, other medications with anticholinergic properties such as hyoscyamine can also be used to decrease symptoms.

Fatur et al. discuss plant-derived tropane alkaloids with anticholinergic properties. These compounds include derivatives from Datura stramonium, Atropa belladonna, Hyoscyamus niger, and Scopolia carniolica.

Incorrect Answers:
Answer 1: Dimercaperol is used in treating heavy metal poisoning with arsenic or mercury. Exposure to arsenic can also present with diarrhea, vomiting, and difficulty breathing; however, the use of arsenate pesticides has been banned for decades so the most common route of exposure in the modern era is contaminated drinking water. Salivation is also more closely associated with organophosphate poisoning.

Answer 3: N-acetylcysteine can be used in the treatment of acetaminophen overdose, which can present with a spectrum of symptoms from mild nausea through fulminant liver failure; however, this toxidrome is caused by an overdose of pills rather than aerosolized exposure from the environment. Furthermore, salivation and bronchospasm are not characteristically seen with acetaminophen overdose.

Answer 4: Physostigmine is a reversible cholinesterase inhibitor that increases the activity of cholinergic signaling. This drug would further increase the effect of organophosphate toxins rather than inhibit it.

Answer 5: Sodium bicarbonate can be used to alkalinize the urine allowing for increased elimination of acidic compounds. For example, salicylate poisoning will present with hyperventilation and metabolic acidosis and can be treated with sodium bicarbonate.

Bullet Summary:
Hyoscyamine can be used to treat cholinergic poisoning when the first-line agents of atropine and pralidoxime are not readily available.