Methanol Poisoning

Methanol is a colorless organic alcohol with mild alcoholic odour, commonly used as a solvent, fuel or antifreeze in the chemical industry. Methanol as a substance is not toxic in itself, but when ingested, it is converted into highly toxic formic acid, which may result in multiple organ failure, blindness, brain damage, and even death.

Outbreaks of methanol poisoning often occur when methanol is added to alcoholic drinks for making money. Fomepizole is one of the effective antidote for methanol poisoning, however, it is not available in most of the affected countries. Médecins Sans Frontières (MSF) is advocating for increased availability and accessibility to fomepizole.

Exposure to Methanol

Methanol, also known as methyl alcohol, wood alcohol or wood spirit, is commonly used for various industrial purposes. Exposure to methanol can occur through ingestion, inhalation and dermal absorption. Small amounts of methanol can also be found in some of the consumer products in our daily lives, such as inks and dyes, paint thinner, and cleaning products. It is also found naturally in some fruits, vegetables, alcoholic and non-alcoholic fermented beverages. With the presence of methanol in our diet, methanol may also be present in our human body in trace amounts.

Methanol itself is not toxic, but when ingested, it transforms into formaldehyde (HCHO) which will then rapidly metabolise to become highly toxic formic acid (CHOOH) and its anion formate (CHOO⁻). The majority of methanol poisoning incidents happen as a result of ingesting adulterated alcoholic drinks. As methanol is cheaper than ethanol – another type of alcohol that is safe for human consumption in moderate quantities – some manufacturers would illegally adulterate alcoholic drinks with methanol to lower the production cost. Unlike water, methanol dissolves in ethanol, diluting the more expensive ethanol without visible evidence of contamination. When the amount of methanol consumed exceeds what the human body can tolerate, it may result in methanol poisoning, causing metabolic acidosis.

Symptoms

The severity of symptoms correlates with the volume of methanol consumed and the amount of ethanol concomitantly ingested. It takes about 12 to 24 hours to produce enough formate for symptoms of poisoning to appear if no ethanol – the most common antidote – is consumed at the same time.

If a mixture of ethanol and methanol is consumed, the delay before symptoms appear can be days (until no ethanol is left in the body). If there is a shorter lapse time (e.g. &lt 6 hours) prior to the onset of symptoms, it is unlikely to be methanol poisoning. The symptoms typically last a few days for the majority of the patients if they survive, but late effects (like blindness or brain damage) is often permanent.

Gastrointestinal:

abdominal pain, nausea, vomiting, poor appetite, gastrointestinal bleeding, pancreatitis;

Neurological:

headache, dizziness, vertigo, amnesia, decreased consciousness, coma, seizure;

Ophthalmologic:

visual disturbances, blurred vision, light sensitivity, partial vision loss, dilated pupils, permanent
blindness;

Others:

respiratory distress or hyperventilation, metabolic acidosis, i.e. increased blood acidity;

Diagnosis

Methanol poisoning can result in a number of symptoms which are similar to other medical conditions, such as diabetic ketoacidosis, alcoholic ketoacidosis, renal failure, septicemia, heart attack, stroke, or severe hangover, making it difficult to get a correct and timely diagnosis. Common misdiagnoses of methanol poisoning include ‘alcohol poisoning’ or ‘sepsis’. The delay in treatment caused by a misdiagnosis is dangerous as prognosis is dependent on how quickly treatment is initiated from point of ingestion.

On the other hand, people being affected often only seek medical care after a significant delay due to the latent period between ingestion and symptom onset, and the fear of being penalised for drinking, especially in countries with an alcohol ban. Even if they are able to seek timely medical care, healthcare workers in settings where poisonings happen may not have the knowledge or expertise to diagnose and treat methanol poisoning properly.

Methanol poisoning outbreaks can easily overwhelm medical facilities, as poisonings regularly happen in groups, for
instance at gatherings and parties, with up to hundreds of people affected at a time and severe cases needing critical care.

Treatments

Without specific treatment, patients can become unconscious and die within a couple of days. A mere 10ml (2 teaspoons) can cause blindness and 30ml (about a mouthful) or more can be fatal. If left untreated, symptoms typically evolve into visual disturbances, coma, brain damage, and death.

The danger of methanol poisoning occurs when the methanol consumed is metabolised into its toxic byproduct (formic acid/ formate) in the body. The accumulation of these toxic substances can result in too much acid in body fluids, and more importantly, it can affect the mitochondrial function in all cells creating a phenomenon known as “cellular hypoxia”. Hence, the aim of treatment is to prevent further metabolism using the antidote ethanol or fomepizole; buffering acidosis with bicarbonate; and using dialysis, if available, to remove methanol and its toxic byproduct from the body. Finally, by giving folic or folinic acid, the endogenous (the body’s own) removal of formic acid is enhanced.

For methanol poisoning treatment protocols and health promotion materials, please visit Resource Centre .

Ethanol (orally or intravenously)

Ethanol is the most commonly used antidote to block the metabolising of methanol. Ethanol works by competing with the metabolic breakdown of methanol, thereby preventing the accumulation of toxic byproducts. However, giving a sufficient amount of ethanol is difficult, and the blood alcohol level is often too low or too high. Therefore, while potentially lifesaving, the preferred antidote fomepizole (see below) is much easier to dose – and with less side-effects – as compared to ethanol, and should be used if available.

Fomepizole

Fomepizole is a more effective and easy to use antidote that does not cause sedation or behavioural changes in patients due to intoxication. Its effectiveness may reduce the need for intubation or dialysis. However, fomepizole is very expensive and unavailable in many parts of the world. The price of fomepizole varies from place to place, ranging from US$500 to US$5,000 per vial.

In 2013, fomepizole was included in the World Health Organization (WHO)’s recommended list of Essential Medicines. However, due to a lack of data on methanol poisoning and the high cost of fomepizole, this antidote is not registered in most countries or approved for emergency reserves. MSF is therefore advocating for increased availability and accessibility to fomepizole.

Bicarbonate(NaHCO3)

Bicarbonate is often used as a buffer to treat the acidic blood and other body tissues, which could reduce toxicity of formic acid /formate and subsequently the acid levels in the body. This is administered in hope that it can temporarily reverse the symptoms. However, bicarbonate usually will only postpone symptoms, leaving the problem unresolved until the metabolism of methanol is blocked.

Prevention

The lack of basic knowledge on methanol poisoning, and shortage of diagnostic equipment, are among the main obstacles in reducing the harmful effects of methanol poisoning. By raising awareness and knowledge on methanol poisoning both among the public and medical community, many lives can be saved and deaths averted within relatively small means.

Medical personnel need to be aware of the specific treatments and use of the antidote for methanol poisoning. Individuals should stop buying or producing illegal alcoholic drinks or liquors sold in unlabeled containers. They should also be aware of the symptoms of methanol poisoning and seek medical help immediately if relevant symptoms develop after 12 to 24 hours or more.