Methanol Toxicity
OVERVIEW
- industrial solvent and synthetic precursor
- highly variable lethal dose
- in itself if is not very toxic, however metabolised to formaldehyde -> formic acid (neurotoxic – retina and optic nerves)
CLINICAL FEATURES
- drunk: windshield fluid, antifreeze, paint, paint removers, gasoline, adhesives, glass cleaner, a solvent/cleaner.
- symptoms develop 12-24 hours post ingestion
- neurology: cerebral oedema, seizures, meningeal irritation, cerebral infarction, blurred vision -> blindness, scotomata, papilloedema, loss of light reflexes
- respiratory failure
- circulatory shock
- GI symptoms
INVESTIGATIONS
- raised osmolar gap
- severe metabolic acidosis (raised anion gap)
- methanol level (not useful acutely due to availability and turn around times)
- normal ionized Ca2+
MANAGEMENT
decreased production of toxic metabolites:
- -> ethanol (competitive inhibitor to alcohol dehydrogenase)
- -> 4-methylapyrazole (same as ethanol but easier to titrate and no sedative effects)
- -> sodium bicarbonate (undissociated formic acid more toxic than the dissociated product – give if pH < 7.3)
- -> folinic acid: 50mg Q4hrly (decreases formate levels and decreases toxicity)
increase elimination:
- -> haemodialysis: effectively and rapidly removed including toxic metabolites
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 – Ethylene glycol inebriation
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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