Methanol toxicity

Short description: Medical condition (poisoning)

Methanol toxicity

Other names| Methanol poisoning, methanol overdose
Molecular structure of methanol
Specialty| Emergency medicine, toxicology
Symptoms| Decreased level of consciousness, ataxia, vomiting, abdominal pain, specific smell on the breath[1][2]
Complications| Blindness, kidney failure, death[1]
Causes| Methanol (such as found in windshield washer fluid)[1][2]
Diagnostic method| Blood acidosis, increased osmol gap, methanol blood level[1][2]
Differential diagnosis| Infections, exposure to other toxic alcohols, serotonin syndrome, diabetic ketoacidosis[2]
Prevention| Consuming safe alcoholic beverages
Treatment| Antidote, hemodialysis[2]
Medication| Fomepizole, ethanol[2]
Prognosis| Good with early treatment[1]
Frequency| 1,700 cases per year (US)[3]

Methanol toxicity (also methanol poisoning) is poisoning from methanol, characteristically via ingestion.[1] Symptoms may include an altered/decreased level of consciousness, poor or no coordination, vomiting, abdominal pain, and a specific smell on the breath.[1][2] Decreased vision may start as early as twelve hours after exposure.[2] Long-term outcomes may include blindness and kidney failure.[1] Ingestion of as little as 3.16 grams of methanol can cause irreversible optic nerve damage, and the oral LD50 for humans is estimated to be 56.2 grams of pure methanol.[4]

Methanol poisoning most commonly occurs following the drinking of tainted alcoholic beverages made with windshield washer fluid.[2] This may be accidental or as part of an attempted suicide. Toxicity may also rarely occur through extensive skin exposure or breathing in fumes.[1] When the body breaks down methanol it results in the creation of metabolite byproducts such as formaldehyde, formic acid, and formate which cause much of the toxicity.[2] The diagnosis may be suspected when there is acidosis or an increased osmol gap and confirmed by directly measuring blood levels.[1][2] Other conditions that can produce similar symptoms include infections, exposure to other toxic alcohols, serotonin syndrome, and diabetic ketoacidosis.[2]

Early treatment increases the chance of a good outcome. Treatment consists of stabilizing the person and using an antidote. The preferred antidote is fomepizole, with ethanol used if this is not available. Hemodialysis may also be used in those where there is organ damage or a high degree of acidosis. Other treatments may include sodium bicarbonate, folate, and thiamine.[2]

Oral methanol toxicity is more common in the developing world.[2] In 2013 more than 1700 cases occurred in the United States. Those affected are usually adults and males.[3] Toxicity to methanol has been described as early as 1856.[5]

## Contents

* 1 Signs and symptoms
* 2 Cause
* 2.1 Surrogate alcohol
* 3 Mechanism
* 4 Treatment
* 5 History
* 6 See also
* 7 References
* 8 External links

## Signs and symptoms

The initial symptoms of methanol intoxication include central nervous system depression, headache, dizziness, nausea, lack of coordination, and confusion. Sufficiently large doses cause unconsciousness and death. The initial symptoms of methanol exposure are usually less severe than the symptoms from the ingestion of a similar quantity of ethanol.[6] Once the initial symptoms have passed, a second set of symptoms arises, from 10 to as many as 30 hours after the initial exposure, that may include blurring, photophobia, snowstorm vision or complete loss of vision, acidosis, and putaminal hemorrhages, an uncommon but serious complication.[7][8] These symptoms result from the accumulation of toxic levels of formate in the blood, and may progress to death by respiratory failure. Physical examination may show tachypnea, and eye examination may show dilated pupils with hyperemia of the optic disc and retinal edema.

## Cause

Ingestion of as little as 4-15 mL of methanol has reportedly caused irreversible optic nerve damage, and the oral LD50 for humans is estimated to be 56.2 grams of pure methanol.[4] The toxicity is attenuated (not removed) when methanol is ingested with ethanol (such as in the case of tainted drinks), increasing the doses required for symptoms and death.[4][9] The reference dose for methanol is 0.5 mg/kg/day.[10]

Methanol is not produced in toxic amounts by fermentation of agricultural products or by subsequent distillation.[11] However, in modern times, in order to comply with regulations reducing the methanol amount is sometimes desired.[12] This can be achieved with the use of a molecular sieve.[13]

### Surrogate alcohol

Because of its similarities in both appearance and odor to ethanol (the alcohol in beverages) or isopropyl alcohol, it is difficult to differentiate between the three.[14] As a result, ethanol is sometimes denatured (adulterated), and made poisonous, by the addition of methanol. The result is known as methylated spirit, "meths" (British use) or "metho" (Australian slang).[15]

Despite its poisonous content, denatured alcohol is sometimes consumed as a surrogate alcohol.[16][17][18]

## Mechanism

Methanol is toxic by two mechanisms. First, methanol (whether it enters the body by ingestion, inhalation, or absorption through the skin) can be fatal due to its CNS depressant properties in the same manner as ethanol poisoning. Second, in a process of toxication, it is metabolized to formic acid (which is present as the formate ion) via formaldehyde in a process initiated by the enzyme alcohol dehydrogenase in the liver.[19] Methanol is converted to formaldehyde via alcohol dehydrogenase and formaldehyde is converted to formic acid (formate) via aldehyde dehydrogenase. The conversion to formate via ALDH proceeds completely, with no detectable formaldehyde remaining.[20] Formate is toxic because it inhibits mitochondrial cytochrome c oxidase, causing hypoxia at the cellular level, and metabolic acidosis, among a variety of other metabolic disturbances.[21]

## Treatment

Methanol poisoning can be treated with fomepizole or ethanol.[19][22][23] Both drugs act to reduce the action of alcohol dehydrogenase on methanol by means of competitive inhibition. Ethanol, the active ingredient in alcoholic beverages, acts as a competitive inhibitor by more effectively binding and saturating the alcohol dehydrogenase enzyme in the liver, thus blocking the binding of methanol. Methanol is excreted by the kidneys without being converted into the toxic metabolites formaldehyde and formic acid. Alcohol dehydrogenase instead enzymatically converts ethanol to acetaldehyde.[19][24] Additional treatment may include sodium bicarbonate for metabolic acidosis, and hemodialysis or hemodiafiltration to remove methanol and formate from the blood.[19] Folinic acid or folic acid is also administered to enhance the metabolism of formate.[19]

## History

There are cases of methanol resistance, such as that of Michael Malloy, whom a group of acquaintances tried and failed to poison with methanol in the early 1930s.[25]

In December 2016, 78 people died in Irkutsk, Russia, from methanol poisoning after ingesting a counterfeit body lotion that was primarily methanol rather than ethanol as labeled. The body lotion, before the event, had been used as a cheap substitute for vodka by the impoverished people in the region despite warnings on the lotion's bottles that it was not safe for drinking and long-standing problems with alcohol poisoning across the country.[26]

During the COVID-19 pandemic, Iranian media reported that nearly 300 people had died and over a thousand became ill due to methanol poisoning in the belief that drinking methanol could help with the disease.[27] In the United States, the Food and Drug Administration discovered that several brands of hand sanitizer manufactured in Mexico during the pandemic contained methanol, and urged the public to avoid using the affected products.[28]

In June 2025, 57 people were poisoned by tainted alcoholic beverages in Jordan. Nine people died from the incident. Jordanian Authorities arrested 12 individuals that are linked to the factory which manufactured the contaminated alcoholic beverages. All 12 were charged with murder and attempted murder.[29][30]

## See also

* Ethylene glycol poisoning

## References

1. ↑ 1.00 1.01 1.02 1.03 1.04 1.05 1.06 1.07 1.08 1.09 "Methanol and ethylene glycol intoxication". Critical Care Clinics 28 (4): 661–711. October 2012. doi:10.1016/j.ccc.2012.07.002. PMID 22998995.
2. ↑ 2.00 2.01 2.02 2.03 2.04 2.05 2.06 2.07 2.08 2.09 2.10 2.11 2.12 2.13 "Toxic Alcohol Ingestion: Prompt Recognition And Management In The Emergency Department". Emergency Medicine Practice 18 (9): 1–20. September 2016. PMID 27538060.
3. ↑ 3.0 3.1 (in en) Ferri's Clinical Advisor 2017: 5 Books in 1. Elsevier Health Sciences. 2016. p. 794. ISBN 978-0-323-44838-3. https://books.google.com/books?id=rRhCDAAAQBAJ&pg=PA794.
4. ↑ 4.0 4.1 4.2 Moon, C. S. (2017). "Estimations of the lethal and exposure doses for representative methanol symptoms in humans". Annals of Occupational and Environmental Medicine 29. doi:10.1186/s40557-017-0197-5. PMID 29026612.
5. ↑ (in en) The Toxicology of Methanol. John Wiley & Sons. 2013. p. 3.4.1. ISBN 978-1-118-35310-3. https://books.google.com/books?id=xSs8oDQV4uYC&pg=PT44.
6. ↑ National Institute for Occupational Safety and Health (22 August 2008). "The Emergency Response Safety and Health Database: Methanol". https://www.cdc.gov/niosh/ershdb/EmergencyResponseCard_29750029.html.
7. ↑ Jafarizadeh, A., Homaie, M., Abdollahi, M., & Niyousha, M. (2023). Time course study of optical coherence tomography angiography in patients with methanol-induced optic neuropathy. BMC ophthalmology, 23(1), 178. https://doi.org/10.1186/s12886-023-02937-x
8. ↑ "Bilateral putaminal hemorrhages: serious complication of methanol intoxication". N Am J Med Sci 5 (10): 623–4. Oct 2013. doi:10.4103/1947-2714.120804. PMID 24350079.
9. ↑ Peterson, Charles D. (1981). "Oral ethanol doses in patients with methanol poisoning". American Journal of Health-System Pharmacy 38 (7): 1024–1027. doi:10.1093/ajhp/38.7.1024. https://academic.oup.com/ajhp/article-abstract/38/7/1024/5200360.
10. ↑ Methanol (CASRN 67-56-1)
11. ↑ "Distillation: Some Purity Considerations". http://www.moonshine-still.com/page7.htm.
12. ↑ Blumenthal, P; Steger, MC; Einfalt, D; Rieke-Zapp, J; Quintanilla Bellucci, A; Sommerfeld, K; Schwarz, S; Lachenmeier, DW (28 April 2021). "Methanol Mitigation during Manufacturing of Fruit Spirits with Special Consideration of Novel Coffee Cherry Spirits.". Molecules 26 (9): 2585. doi:10.3390/molecules26092585. PMID 33925245.
13. ↑ Hui-Ling Ma; Xiu-Ping Yang; Ying Zuo (15 April 2006). "Study on Method of Decreasing Methanol in Apple Pomace Spirit". Food Science 27 (4): 138–142. http://www.spkx.net.cn/EN/abstract/abstract15544.shtml.
14. ↑ Wade, Leroy G.. "Physical properties of alcohols" (in en). Britannica. https://www.britannica.com/science/alcohol/Physical-properties-of-alcohols. Retrieved 2024-08-18.
15. ↑ "Resources - Promote and practice". https://healthinfonet.ecu.edu.au/key-resources/resources/27191/?title=Metho++methylated+spirits+++It+s+not+a+drink+&contenttypeid=1&contentid=27191_1.
16. ↑ "Alcohol poisoning death toll in Russian city rises to 49". Associated Press. 19 December 2016. https://www.apnews.com/c0c419587e7d44ec8a6c6ac2685b8f2a/Alcohol-poisoning-death-toll-in-Russian-city-rises-to-48.
17. ↑ Blum D (2010). The Poisoner's Handbook: murder and the birth of forensic medicine in Jazz Age New York. New York: Penguin Books. p. 231. ISBN 978-0-14-311882-4.
18. ↑ "Methanol poisoning cases from tainted alcohol in Jordan rise to 57, death toll stays at 9". Roya News. 1 July 2025. https://en.royanews.tv/news/60866.
19. ↑ 19.0 19.1 19.2 19.3 19.4 "A seaman with blindness and confusion". BMJ 339. 2009. doi:10.1136/bmj.b3929. PMID 19793790. http://www.bmj.com/cgi/content/full/339/sep30_1/b3929.
20. ↑ "Lack of a role for formaldehyde in methanol poisoning in the monkey". Biochem. Pharmacol. 28 (5): 645–9. 1979. doi:10.1016/0006-2952(79)90149-7. PMID 109089.
21. ↑ "Methanol and formic acid toxicity: biochemical mechanisms". Pharmacol. Toxicol. 69 (3): 157–63. September 1991. doi:10.1111/j.1600-0773.1991.tb01290.x. PMID 1665561.
22. ↑ "Fomepizole in the treatment of poisoning". Pediatrics 107 (1): 170. January 2001. doi:10.1542/peds.107.1.170. PMID 11134450. http://pediatrics.aappublications.org/cgi/content/full/107/1/170.
23. ↑ "Fomepizole for ethylene glycol and methanol poisoning". The New England Journal of Medicine 360 (21): 2216–2223. May 2009. doi:10.1056/NEJMct0806112. PMID 19458366.
24. ↑ Fundamentals of Biochemistry: Life at the Molecular Level (5th ed.). Hoboken, NJ: Wiley. 2008.
25. ↑ The Poisoner's Handbook: murder and the birth of forensic medicine in Jazz Age New York. New York: Penguin Books. 2010. p. 231. ISBN 978-0-14-311882-4.
26. ↑ "Alcohol poisoning death toll in Russian city rises to 49". Associated Press. 19 December 2016. https://www.apnews.com/c0c419587e7d44ec8a6c6ac2685b8f2a/Alcohol-poisoning-death-toll-in-Russian-city-rises-to-48.
27. ↑ Karimi, Nasser; Gambrell, Jon (27 March 2020). "In Iran, false belief a poison fights virus kills hundreds". https://apnews.com/6e04783f95139b5f87a5febe28d72015.
28. ↑ "FDA Updates on Hand Sanitizers with Methanol". https://www.fda.gov/drugs/drug-safety-and-availability/fda-updates-hand-sanitizers-methanol.
29. ↑ "Methanol poisoning cases from tainted alcohol in Jordan rise to 57, death toll stays at 9". Roya News. 1 July 2025. https://en.royanews.tv/news/60866.
30. ↑ "Twelve charged with murder in Jordan's contaminated alcohol case". Roya News. 1 July 2025. https://en.royanews.tv/news/60872.

## External links

Classification|

* ICD-10: T51.1
* ICD-9-CM: E980.9

|

* v
* t
* e

* Poisoning
* Toxicity
* Overdose (T36–T65, 960–989)

History of poison

Inorganic|

| Metals|

| Toxic metals|

* Beryllium
* Cadmium
* Lead
* Mercury
* Nickel
* Silver
* Thallium
* Tin

|

Dietary minerals|

* Chromium
* Cobalt
* Copper
* Iron
* Manganese
* Zinc

Metalloids|

* Arsenic

Nonmetals|

* Sulfuric acid
* Selenium
* Chlorine
* Fluoride

Organic|

| Phosphorus|

* Pesticides
* Aluminium phosphide
* Organophosphates

|

Nitrogen|

* Cyanide
* Nicotine
* Nitrogen dioxide poisoning

CHO|

* alcohol
* Ethanol
* Ethylene glycol
* Methanol
* Carbon monoxide
* Oxygen
* Toluene

Pharmaceutical|

| Drug overdoses|

| Nervous|

* Anticholinesterase
* Aspirin
* Barbiturates
* Benzodiazepines
* Cocaine
* Lithium
* Opioids
* Paracetamol
* Tricyclic antidepressants

|

Cardiovascular|

* Digoxin
* Dipyridamole

Vitamin poisoning|

* Vitamin A
* Vitamin D
* Vitamin E
* Megavitamin-B6 syndrome

Biological1|

| Fish / seafood|

* Ciguatera
* Haff disease
* Ichthyoallyeinotoxism
* Scombroid
* Shellfish poisoning
* Amnesic
* Diarrhetic
* Neurotoxic
* Paralytic

|

Other vertebrates|

* amphibian venom
* Batrachotoxin
* Bombesin
* Bufotenin
* Physalaemin
* birds / quail
* Coturnism
* snake venom
* Alpha-Bungarotoxin
* Ancrod
* Batroxobin

Arthropods|

* Arthropod bites and stings
* bee sting / bee venom
* Apamin
* Melittin
* scorpion venom
* Charybdotoxin
* spider venom
* Latrotoxin / Latrodectism
* Loxoscelism
* tick paralysis

Plants / fungi|

* Cinchonism
* Ergotism
* Lathyrism
* Locoism
* Mushrooms
* Strychnine

1 including venoms, toxins, foodborne illnesses.

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