Methanol Poisoning 101: Causes and Warning Signs

December 1, 2024

by Elizabeth Howe, Writer / Editor

AI generated image of a woman and man at a tropical bar

Disclaimer: This article was originally written in 2022 for my Medium Blog. Given the recent tragedy in Laos, I've decided to repost this article to help improve understanding of the dangers of methanol poisoning and how to stay safe.

While traveling overseas in Thailand and Bali this past month I was reminded of something devastating that I learned in a chemistry class at university: in some holiday destinations, alcohol may be contaminated with methanol. Methanol is toxic and consuming it can result in methanol poisoning, which is a serious, life-threatening condition requiring medical attention.

Alcohol that we drink contains ethanol, not methanol

Ethanol is the compound in alcohol that we drink that causes the intoxication effects. It is a clear and colorless liquid. Drinking ethanol in alcoholic beverages is safe in moderation, although it should never be consumed on its own.

Methanol is typically used as an industrial solvent and in windshield washer fluids. It is similar to ethanol in color, taste, and smell. Methanol and ethanol are also very similar on a molecular level.

Chemical structures of Ethanol and Methanol

Methanol contamination in alcoholic beverages may be a result of errors in the distillation or fermentation of homemade alcohol.¹ Additionally, methanol is cheaper to produce than ethanol so it is sometimes added illegally to beverages instead of, or as well as, ethanol.²

Methanol poisoning can be treated if it is diagnosed within 10–30 hours of ingestion. But, consuming 25–90 mL of methanol can be fatal if medical attention is not sought soon enough.²

For comparison, a blood alcohol (ethanol) level of 0.4% is dangerous, potentially leading to coma and death.⁶ For an 80 kg male to reach this level of intoxication, within one hour he would have to consume approximately 16 shots of 40% vodka (assuming ideal conditions with no metabolism during the hour). This is about 280 mL of ethanol.

Disclaimer: You should NOT consume this much alcohol. The amount of alcohol that is dangerous for you will vary based on your body and alcohol tolerance. Please only use this information as a comparison to show how a small amount of methanol can be fatal.

Where should you be concerned about methanol poisoning?

Outbreaks of methanol poisoning have occurred in a number of popular holiday destinations. For example, in 2009, 25 people died in Indonesia as a result of drinking alcohol containing methanol. In 2011, 130 people, and again in 2015, 27 people died after drinking contaminated alcoholic beverages in India.³

In 2014, the World Health Organisation (WHO) warned that instances of methanol poisoning were increasing in some countries. These countries included:

Ecuador
Estonia
Gambia
Ganda
India
Indonesia
Kenya
Libya
Norway
Pakistan
Turkey

If you’re traveling to any of these countries, it’s important to be aware of how to avoid drinking methanol-contaminated alcohol.

How to tell if your drink contains methanol or ethanol

Initially, it can be difficult to tell whether a drink contains methanol as it is similar in both taste and smell to ethanol. Early symptoms of methanol poisoning often resemble the typical signs of intoxication.¹˒²

Confusion
Dizziness
Headache
Lack of coordination
Nausea

What happens if you drink methanol?

If you have consumed methanol, once the typical ‘drunk’ symptoms have subsided, it is likely that you will experience a ‘latent period’.² This means that there will be a period of time when you show very few or no symptoms. This period may last for 12–24 hours after methanol consumption.

After the latent period, acute symptoms will begin to appear.⁵ If you experience any of these symptoms 12–24 hours after consuming alcohol, you should seek medical attention immediately.

Blue/purple coloring of fingers or lips
Blurry vision
Epigastric pain (pain directly below your ribs)
Headache
Nausea
Shortness of breath
Vomiting
Weakness of muscles

If medical attention is not sought out, severe symptoms may begin to appear.²˒⁴˒⁵ Severe symptoms of methanol poisoning include:

Abdominal pain
Blurred vision and blindness
Breathing difficulty
Comas
Confusion or memory loss
Convulsions
Hypothermia
Nausea
Permanent neurologic dysfunction
Reduced heart rate
Seizures
Stupor (near unconsciousness)
Vomiting

If medical attention is not obtained, coma and eventually death may occur.

But how does methanol cause these symptoms?

You might think that because methanol and ethanol have a very similar structure they would react similarly within the body.

Well, you would be somewhat right. Methanol and ethanol are metabolised in a similar manner. But, the end products of their metabolism differ and the end product is what causes the toxicity of methanol.

To understand the effects of methanol, let’s start with how ethanol is metabolised.

Ethanol (or ‘alcohol’) enters the body and travels to the liver.
An enzyme called alcohol dehydrogenase converts the ethanol molecules into acetaldehyde.
Acetaldehyde is then converted into acetate by an enzyme called aldehyde dehydrogenase.⁷
Acetate is then broken down into water and carbon dioxide.
Water and carbon dioxide are easily eliminated from the body.⁸

The biochemical pathway of ethanol in the liver

It’s important to note the effects of acetaldehyde on the body. Although ethanol is deemed safe to consume in moderation, acetaldehyde is highly toxic and carcinogenic.⁸ Acetaldehyde doesn’t typically stay in the body long; it is quickly converted to acetate.

However, when large amounts of ethanol are consumed, alcohol is consumed regularly, or if the liver is already damaged, acetaldehyde can cause the serious effects associated with alcohol consumption such as liver damage.

The metabolism of methanol uses the same enzymes as ethanol metabolism.

Methanol enters the body and travels to the liver
Methanol is converted to formaldehyde by alcohol dehydrogenase.
Formaldehyde then is converted to formic acid by aldehyde dehydrogenase.¹˒²
Formic acid is released into the bloodstream.
Formic acid is not easily removed from the body and instead, accumulates within the bloodstream.¹

The biochemical pathway of methanol in the liver

Formic acid is the molecule that causes the damage associated with methanol poisoning.⁴ When formic acid accumulates in the blood, it causes the acidity of the blood to increase, resulting in a condition called metabolic acidosis.²˒⁵

It is dangerous to have acidic blood as it causes all of the systems in the body to weaken and causes the symptoms associated with methanol poisoning.

To summarise these differences here’s a comparison of methanol and ethanol metabolism

Comparison of the biochemical pathways of ethanol and methanol

What to do if you have consumed methanol

If you are showing symptoms of methanol poisoning the most important thing to do is contact emergency services. Methanol poisoning can be successfully treated if it is diagnosed within 10–30 hours after consumption.²

It is best to have someone with you while you wait for emergency services as they can help you tell the medical professionals how much you had to drink, the symptoms you are experiencing, and any other information that they need.

How is methanol poisoning treated?

There are two main treatment options for methanol poisoning. Fomepizole is the first-line antidote (meaning that it is the go-to treatment). If fomepizole is not available, ethanol may be used instead.²˒⁵

Fomepizole treatment

Fomepizole is the first choice for the treatment of methanol poisoning.²˒⁵ Fomepizole works by inhibiting the activity of alcohol dehydrogenase, stopping the metabolism of methanol at step 2 (in the image above).⁵ Preventing the metabolism of methanol stops the formation of formic acid, thereby halting the progression of methanol poisoning.

Unmetabolised methanol is not easily removed from the body; however, it has a half-life of 30–85 hours. This means that within 30–85 hours (about 1–3.5 days) half of the unmetabolised methanol in the body will have broken down.¹

Fomepizole is administered intravenously (via an IV line into a vein). It has clear dosage guidelines, making it easy for doctors to administer. Unfortunately, fomepizole is not always available as it is fairly expensive.¹ If fomepizole is not available, ethanol may be used to treat methanol poisoning.²

Ethanol treatment

Ethanol is the second-line treatment option for methanol poisoning. When ethanol is administered, the liver will metabolise ethanol before methanol. This allows time for methanol to be removed from the body before it can be metabolised.²

Ethanol can be administered intravenously or orally. It is much harder to accurately dose than fomepizole, making it a bit more difficult for doctors to use as a treatment. Additionally, treatment with ethanol will cause the intoxication associated with alcohol consumption.¹

If you have symptoms of methanol poisoning, you could consume ethanol such as high doses of vodka or whisky while waiting for emergency services. However, if you choose to do this, it is best to discuss how to do this with the emergency services on the phone.

It’s important to be aware of how much alcohol you are consuming. Ideally, have someone else with you who can help you discuss the situation with a medical professional, including how much ethanol you consumed.

Additionally, make sure that you drink alcohol from a trusted source, e.g. bottled and unopened vodka or whisky from a brand that you know. Do not drink any of the alcohol you were drinking before your symptoms started.

Hemodialysis

Hemodialysis is a treatment that may be used in addition to either fomepizole or ethanol treatment.¹ Hemodialysis uses a machine called a dialyser to filter the blood and remove toxins such as methanol so that it cannot be metabolised. You might have heard of hemodialysis as a common treatment for kidney disease.

During hemodialysis treatment, a needle is inserted into your arm which is attached to a tube. Your blood then flows into the needle and through the tube into the dialyzer. The filtered blood then flows out of the machine, into another tube, and back into the arm via another needle.

How to avoid methanol poisoning while holidaying overseas

The easiest way to avoid consuming methanol is to simply not drink any alcohol. However, that might not be ideal for many people while holidaying. So, here are some simple guidelines to help you avoid methanol poisoning.

Drink canned or bottled alcohol. Instead of purchasing cheap tap beer, spirits, or wine at a bar, choose bottled or canned RTDs or beer.

Choose alcohol from trusted brands that you know. As methanol is most likely present in cheap or homemade alcohol, the best way to avoid methanol poisoning is to drink alcohol from trusted brands and retailers.

Avoid cocktails. Unless you’re at a trusted resort or high-end bar, it is best to avoid drinking cocktails. Generally, when you purchase a cocktail, you don’t see exactly what alcohol is being added. To be safe, it is best to avoid drinking cocktails when holidaying in places where there is a risk of methanol poisoning.

Look at the price. Although many places such as Indonesia are known for their cheap holidays and alcohol, it is important to know how cheap is too cheap. The best way to know this is to compare the prices of the cheap drinks to those of similar drinks from brands that you know. If the pricing is significantly cheaper, then it’s probably not worth the risk.

Summary

Consuming cheap or homemade alcohol may result in methanol poisoning. Instances of methanol poisoning are more common in places such as Indonesia and India. To avoid methanol poisoning when visiting these places, it is best to consume bottled or canned alcohol from brands that you trust and avoid cocktails and super cheap alcohol.

Remember, if the price seems too good to be true, it probably is.

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