Sodium Channel Blocker Toxicity
AGENTS
- local anesthetic agents
- tricyclic antidepressants
- carbamazepine (in very high doses)
- dextropropoxyphene
- antiarrhythmics e.g. flecainide, quinine
- propanolol
- thioridizine
- phenothiazines (not usually clinically significant)
- amantidine
NB. phenytoin and sodium valproate do not usually present with features of sodium channel blockade in overdose.
CLINICAL FEATURES
- CVS: arrhythmias, prolonged PR, QRS widening and secondary QT effects, hypotension, pulmonary oedema
- CNS: mild ataxia -> coma -> seizures, peri-oral numbness/tingling, tinnitus
INVESTIGATIONS
- drug levels rarely helpful
- ECG: positive QRS in II, dominant R wave in aVR, QRS duration > 100ms
- high anion gap metabolic acidosis
SPECIFIC MANAGEMENT AND TRIGGERS FOR INTERVENTION
- NaHCO3 is the mainstay for QRS >140, cardiotoxicity, seizures
- benzodiazepines for seizures
- activate charcoal: severe OD, one dose after airway secured; MDAC for carbamezepine
- intra-lipid: LA toxicity with ECG changes
- CVVHDF: carbamazepine (alternative to charcoal hemoperfusion)
- ECMO: cardiac arrest
References and Links
CCC Toxicology Series
General
Approach to acute poisoning, ECGs in Tox, Evidenced-based Tox, Toxicology literature summaries, Does anti-venom work?
Toxins / Overdose
Amphetamines, Barbituates, Benzylpiperazine, Beta Blockers, Calcium Channel Blocker, Carbamazepine, Carbon Monoxide, Ciguatera, Citrate, Clenbuterol, Cocaine, Corrosive ingestion, Cyanide, Digoxin, Ethanol, Ethylene Glycol, Iron, Isoniazid, Lithium, Local anaesthetic, Methanol, Monoamine oxidase inhibitor (MAOI), Mushrooms (non-hallucinogenic), Opioids, Organophosphate, Paracetamol, Paraquat, Plants, Polonium, Salicylate, Scombroid, Sodium channel blockers, Sodium valproate, Theophylline, Toxic alcohols, Tricyclic antidepressants (TCA)
Envenomation
Marine, Snakebite, Spider, Tick paralysis
Syndromes
Alcohol withdrawal, Anticholinergic syndrome, Cholinergic syndrome, Drug withdrawals in ICU, Hyperthermia associated toxidromes, Malignant hyperthermia (MH), Neuroleptic malignant syndrome (NMS), Opioid withdrawal, Propofol Infusion Syndrome (PrIS) Sedative toxidrome, Serotonin syndrome, Sympatholytic toxidrome, Sympathomimetic toxidrome
Decontamination
Activated Charcoal, Gastric lavage, GI Decontamination
Enhanced Elimination
Enhanced elimination, Hyperbaric therapy for CO
Antidotes
Antidote summary, Digibind, Glucagon, Flumazenil, HIET – High dose euglycaemic therapy, Intralipid, Methylene Blue, N-Acetylcysteine (NAC), Naloxone
Miscellaneous
Cocaine chest pain, Digoxin and stone heart theory, Hyperbaric oxygen, Hypoxaemia in tox, Liver failure in tox, Liver transplant for paracetamol, Methaemoglobinaemia, Urine drug screen
- Tox Conundrum – Another TCA Overdose!
- Tox Conundrum – Tricyclic antidepressant toxicity
- ECG Library – Overdose: TCA
Critical Care
Compendium
Chris is an Intensivist and ECMO specialist at The Alfred ICU, where he is Deputy Director (Education). He is a Clinical Adjunct Associate Professor at Monash University, the Lead for the Clinician Educator Incubator programme, and a CICM First Part Examiner.
He is an internationally recognised Clinician Educator with a passion for helping clinicians learn and for improving the clinical performance of individuals and collectives. He was one of the founders of the FOAM movement (Free Open-Access Medical education) has been recognised for his contributions to education with awards from ANZICS, ANZAHPE, and ACEM.
His one great achievement is being the father of three amazing children.
On Bluesky, he is @precordialthump.bsky.social and on the site that Elon has screwed up, he is @precordialthump.
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