What is Methanol Toxicity?
Methanol (CH3OH) is a harmful type of alcohol that can be found in many household and industrial products. When we talk about “toxic alcohols,” we’re referring to methanol, ethylene glycol, and isopropyl alcohol. Coming into contact with methanol can be very dangerous and can lead to serious health problems and even death if not treated.
Methanol poisoning often happens because of accidental or deliberate swallowing, or even during large-scale accidents due to mistakes made in the distilling and fermenting processes, or the contamination of drinks. Methanol can be found in products such as windshield washer fluid, gas line antifreeze, carburetor cleaner, copy machine fluid, perfumes, food warming fuel, and other types of fuels. Contact with these substances can result in different levels of toxicity and can require anything from close observation of lab results to specific antidote treatment and dialysis (a medical procedure to remove waste and excess water from the blood).
The main treatments for methanol poisoning are ethanol or fomepizole, and unlike in cases of ethylene glycol toxicity (another type of harmful alcohol), dialysis is often recommended.
What Causes Methanol Toxicity?
Methanol, a type of alcohol, can enter the body and cause harm in three ways: through eating or drinking it, absorbing it through the skin, or breathing it in. Most often, it happens when someone drinks windshield washer fluid on purpose to harm themselves. However, it can also happen by accident, like when kids touch or taste things because they’re curious.
Unfortunately, some people abuse methanol as a substitute for regular alcohol (ethanol) using products like fuel for food warmers or carburetor cleaner. These products are illicitly used and are harmful when inhaled.
Risk Factors and Frequency for Methanol Toxicity
People who are most likely to be at risk include toddlers and young children who are still learning about their surroundings, individuals who consume too much alcohol, and people who are feeling suicidal. In most instances, these cases happen as one-off events. However, there have been instances where large outbreaks happened because of contaminated alcohol or improper alcohol distilling processes.
Signs and Symptoms of Methanol Toxicity
It can be difficult to get a full understanding of an intentional self-harm or substance abuse situation as patients often will not admit or minimize their actions. This makes diagnosing toxic alcohol exposure especially challenging, and it is the doctor’s responsibility to consider this as the cause of some findings, such as metabolic acidosis with an elevated anion gap. Eating or drinking something poisonous, on the other hand, is often self-reported or witnessed.
People who come in within 12 to 24 hours after ingesting the toxic substance might seem fine, a period commonly referred to as the “latent period”. Symptoms like nausea, vomiting, and abdominal pain usually follows. As the metabolic acidosis or the body’s acid levels become too high, the central nervous system starts to slow down, leading to depression and hyperventilation.
Eye problems related to retinal toxicity might appear in the form of blurry vision, decreased eyesight, light sensitivity, and seeing halos around objects. In such cases, a physical examination might reveal swelling of the optic nerve (papilledema), hyperemia or increased blood flow in the optic disc, and malfunctioning pupils. Symptoms related to basal ganglia toxicity, an area in the brain, may not be evident in the initial stages because of mental status depression and the severity of the condition. If left untreated, the person may fall into a coma, or experience breathing and circulatory system failure, which can lead to death.
- Initially there may be no symptoms (latent period)
- Nausea
- Vomiting
- Abdominal pain
- Depression
- Hyperventilation
- Blurry vision
- Decreased eyesight
- Light sensitivity
- Seeing halos around objects
Testing for Methanol Toxicity
If you’ve swallowed methanol, you might not show any symptoms initially but could become very ill over time. This substance can cause problems with your body’s normal processing and can lead to damage in your organs.
To figure out if you’ve consumed methanol, your doctor may consider your medical history and current symptoms. They’ll also likely carry out several tests. One such test might be an electrocardiogram, which checks how your heart is functioning. You may also have routine tests to check on your general health, such as a basic metabolic panel, which looks at your kidney function, blood sugar levels, and electrolyte balance, and an acetaminophen concentration test, which measures the level of a common pain medication in your body.
If your doctor suspects you might have harmed yourself, they might order additional tests. These could include a complete blood count (blood cell numbers), tests for liver function, and tests for pregnancy. They might also check for substances in your blood or urine that could suggest certain medical conditions.
Unfortunately, testing to conclusively confirm whether you’ve ingested toxic alcohols like methanol can be a bit tricky. This is because it usually requires a specific type of test called gas chromatography, which is not available in all hospitals.
Meanwhile, early after ingesting, you might have a higher osmolar gap which means there are substances in your blood that can pull water from your cells. As part of surface-level identification, your doctor might close monitor changes in your body physiology and keep a watch for development of metabolic acidosis which is a condition wherein your body starts producing too much acid or your kidneys are not removing enough acid from your body.
If your doctor is concerned about methanol poisoning, they’ll be on the watch for certain key symptoms, particularly vision problems. They’ll likely also test for salicylate toxicity, a kind of poisoning that can happen if you take too much aspirin or other salicylate-containing medicines.
Finally, your doctor might calculate a theoretical concentration of toxic alcohol in your blood. This might be particularly useful in cases where a small amount of alcohol has been ingested accidentally. Keep in mind that the term “alcohol” in this case doesn’t just mean ethanol, which is the type of alcohol found in alcoholic beverages.
While all of these tests and observations can be helpful, the only real confirmation of toxic alcohol ingestion is a serum concentration test that demonstrates you’ve been exposed. If you develop conditions like metabolic acidosis (a high level of acid in your blood) along with other symptoms, it’s possible you’ve ingested a toxic alcohol.
Treatment Options for Methanol Toxicity
If someone has been poisoned by methanol, which is a toxic form of alcohol, several different ways to treat the condition are available. These include supportive care, therapeutic drugs like fomepizole and ethanol, dialysis, and potentially folate. Fomepizole and ethanol are antidotes; they work by blocking an enzyme called alcohol dehydrogenase, preventing it from converting methanol into formate, a toxin harmful to the body.
Fomepizole is often preferred for its precise dosage and lack of side effects like inebriation, though it is more expensive. Ethanol is cheaper but more challenging to manage, requiring strict monitoring of the concentration in the blood, and can also make patients feel drunk, possibly requiring intensive care.
Treatment is recommended if methanol concentration in the blood is high or if the body’s acid levels are increasing despite attempts to normalize them, especially if methanol ingestion is suspected. The exact methanol concentration to begin treatment varies, but typically, concentrations greater than 20 to 25 mg/dL prompt treatment, although in some cases, 32 mg/dL is the threshold, especially if there is mild or no acidosis, and there is no evidence of damage to body organs. After receiving strong therapies like fomepizole, there is a window of about 12 hours in which methanol metabolism is paused, giving enough time to assess the methanol levels and prepare dialysis if necessary.
When methanol treatment begins, either fomepizole or ethanol is used to stop the conversion of methanol into its harmful form, formate. Once blocked, the clear out time of methanol is extended from approximately 8.5 mg/dL/hr to an effective half-life of 45 to 90 hours. Fomepizole is given intravenously.
Administering ethanol is more complex, harder to monitor, and has the side effect of making the patient feel drunk. Therefore, it should only be given if fomepizole is not available. When used, the patient’s blood alcohol concentration is closely monitored to ensure it is within a specified range. Both intravenous and oral ethanol treatments are available. Either way, the dosage administered is adjusted during dialysis.
Patients with toxic methanol poisoning are often considered for hemodialysis—a procedure to remove waste products from the blood—due to methanol and formate’s low distribution volume and lack of protein binding, making them removable by this process. Hemodialysis also can reduce a patient’s hospital stay duration. Dialysis is only strictly needed when there is a new visual impairment in the presence of metabolic acidosis but may also be considered in other serious cases.
Another potential treatment for methanol toxicity includes the administration of folate. Folate might help the body break down the toxic metabolite, formate, into harmless carbon dioxide and water. Finally, if a patient’s symptoms appear severe, the patient is not responding to treatment, requires dialysis, or is being treated with ethanol as an antidote, admission to the intensive care unit may be necessary.
What else can Methanol Toxicity be?
When trying to diagnose toxicity from alcohol ingestion, doctors need to consider other conditions that might cause similar symptoms. This can include other things that could cause metabolic acidosis, as well as consider the possibility that different types of alcohol might have been consumed.
It’s essential to take into account toxins that can cause metabolic acidosis. These include:
- Salicylates (found in aspirin)
- Acetaminophen (a common pain reliever)
- Iron
- Carbon monoxide
- Cyanide
- Conditions like alcoholic ketoacidosis
- Ingestion of other toxic alcohols, like ethylene glycol, diethylene glycol, or toluene
It’s also possible that a person might have consumed substances or agents that contain more than one type of alcohol or toxic ingredient.
Apart from these toxic substances, non-toxic causes should also be contemplated. These might include diabetes ketoacidosis, sepsis (a severe infection), and uremia (a condition involving the kidneys).
What to expect with Methanol Toxicity
If an eye condition or brain damage known as retinal toxicity and basal ganglia toxicity respectively are diagnosed swiftly and treated promptly, patients generally recover. These conditions may result in lasting symptoms if not managed appropriately.
However, if a patient comes in for treatment late or if the condition isn’t diagnosed quickly, there might be serious health complications and even a risk of death. Therefore, quick diagnosis and treatment are crucial.
Possible Complications When Diagnosed with Methanol Toxicity
Complications:
- Changes in body’s acid and base balance
- Lasting problems with vision
- Conditions similar to Parkinson’s disease
- Falling into a coma
- Problems with breathing function
- Issues with blood circulation
- Difficulties related to dialysis, a kidney treatment
- Potential death
