Episode 911: Anticholinergic Toxicity

Contributor: Taylor Lynch MD Educational Pearls: Anticholinergics are found in many medications, including over-the-counter remedies Medications include: Diphenhydramine Tricyclic antidepressants like amitriptyline Atropine Antipsychotics like olanzapine Antispasmodics - dicyclomine Jimsonweed Muscaria mushrooms Mechanism of action involves competitive antagonism of the muscarinic receptor Symptomatic presentation is easily remembered via the mnemonic: Dry as a bone - anhidrosis due to cholinergic antagonism at sweat glands Red as a beet - cutaneous vasodilation leads to skin flushing Hot as a hare - anhidrotic hyperthermia Blind as a bat - pupillary dilation and ineffective accommodation Mad as a hatter - anxiety, agitation, dysarthria, hallucinations, and others Clinical management ABCs Benzodiazepines for supportive care, agitation, and seizures Sodium bicarbonate for TCA toxicity due to widened QRS Activated charcoal if patient present < 1 hour after ingestion Temperature monitoring Contact poison control with questions Physostigmine controversy Acetylcholinesterase inhibitor Black box warning for asystole and seizure Contraindicated in TCA overdoses Crosses blood-brain barrier, so useful for TCA overdoses Indicated only in certain anticholinergic overdose with delirium Disposition Admission criteria include: symptoms >6 hours, CNS findings, QRS prolongation, hyperthermia, and rhabdomyolysis ICU admission criteria include: delirium, dysrhythmias, seizures, coma, or requirement for physostigmine drip References 1. Arens AM, Shah K, Al-Abri S, Olson KR, Kearney T. Safety and effectiveness of physostigmine: a 10-year retrospective review<sup/>. Clin Toxicol (Phila). 2018;56(2):101-107. doi:10.1080/15563650.2017.1342828 2. Nguyen TT, Armengol C, Wilhoite G, Cumpston KL, Wills BK. Adverse events from physostigmine: An observational study. Am J Emerg Med. 2018;36(1):141-142. doi:10.1016/j.ajem.2017.07.006 3. Scharman E, Erdman A, Wax P, et al. Diphenhydramine and dimenhydrinate poisoning: An evidence-based consensus guideline for out-of-hospital management. Clin Toxicol. 2006;44(3):205-223. doi:10.1080/15563650600585920 4. Shervette RE 3rd, Schydlower M, Lampe RM, Fearnow RG. Jimson "loco" weed abuse in adolescents. Pediatrics. 1979;63(4):520-523. 5. Woolf AD, Erdman AR, Nelson LS, et al. Tricyclic antidepressant poisoning: An evidence-based consensus guideline for out-of-hospital management. Clin Toxicol. 2007;45(3):203-233. doi:10.1080/15563650701226192 Summarized by Jorge Chalit, OMSIII | Edited by Jorge Chalit