Episode Details

Episode 105: Antidotes to toxidromes. Some poisonings share common signs and symptoms and may be treated with antidotes without laboratory confirmation of the offending agent. Dr. Francis discussed with Dr. Arreaza some of those toxidromes and how to treat them. Written by Aida Francis, MD. Participation by Hector Arreaza, MD. Definitions: • Antidotes are substances given as a remedy that inhibit the effects of another drug of abuse or poison. Most are not 100% effective and fatality is still possible after administration. • Toxidrome is a constellation of signs and symptoms caused by an overdose or exposure to chemicals or drugs that interact with neuroreceptors. Toxidrome is the combination of the word “toxin” and “syndrome”. Management strategies of toxidromes are determined by the signs and symptoms even when the causative agent has not been identified. A little bit of Background: The World Health Organization reported that 13% of deaths caused by poisonings are children and young adults. Intentional poisoning attempts are more frequent among adolescent women than men. It is difficult to evaluate poisoned patients because they are too altered to provide history and there is often not enough time to perform a physical exam or obtain serum studies prior to life-saving interventions. To diagnose a toxidrome clinically, you need three elements: pupil size, temperature, and bowel sounds. For example: Pinpoint pupils with hyperactive bowel sounds point to cholinergic toxidrome, and dilated pupils with high temperature, and hypoactive bowel sounds point to anticholinergic (see details below). Pinpoint pupils -> Bowel sounds -> Hyperactive: CHOLINERGIC -> Hypoactive: OPIOIDS Normal or dilated pupils -> Temperature -> High -> Bowel sounds -> Hyperactive: SYMPATHOMIMETIC -> Hypoactive: ANTICHOLINERGIC -> Normal or Low -> Bowel sounds -> Hyperactive: HALLOCUNOGENIC -> Hypoactive: SEDATIVE-HYPNOTICS Anticholinergic Toxidrome and the Physostigmine antidote: • Anticholinergics inhibit the binding of acetylcholine to the muscarinic receptors in the central nervous system and the parasympathetic nervous system. Examples of anticholinergics include atropine and tiotropium. Other substances that may cause anticholinergic toxidrome include antihistamines (especially first-generation: diphenhydramine), antipsychotics (quetiapine), antidepressants (TCAs, paroxetine), and antiparkinsonian drugs (benztropine). Symptoms of toxicity include tachycardia, non-reactive mydriasis, anhidrosis, dry mucous membranes, skin flushing, decreased bowel sounds, and urinary retention. Neurological symptoms include delirium, confusion, anxiety, agitation, mumbling, visual hallucination, and strange behavior. Neurological symptoms last longer because of the anticholinergic lipophilic properties which cause them to distribute into fatty organs and tissues like the brain. “Mad as a hatter, red as a beet, blind as a bat, hot as a hare, dry as a bone” [Spanish: loco como una cabra, rojo como un tomate, ciego como un topo, seco como una piedra, caliente como el infierno] • The antidote for anticholinergic toxidrome is physostigmine. It is an acetylcholinesterase inhibitor and prevents the metabolism of acetylcholine. This increases the level of acetylcholine in both the central nervous system and peripheral nervous system. Physostigmine can cause seizures and arrhythmia, so close monitoring in the hospital is required during treatment. Cholinergic toxidrome and its antidotes atropine and pralidoxime: Acetylcholine is part of the parasympathetic nervous system and cholinergic substances can induce a parasympathetic response. Some of these substances include pesticides, organophosphates, carbamate, and nerve gas. Chlorpyrifos had been used to control insects in homes and fields since 1965. It has been used in our crops in Bakersfield, and the most recent mass exposure was in May 2017. it was