|ID:124 ||Methanol||Search Links: General Info : Protocols : Patient Info|
|Description||A common contaminant of illegal alcohol products and many fluids which can be ingetsed by accident or in cases of self poisoning. PLEASE CONTACT THE DUTY BIOCHEMIST BEFORE SENDING SAMPLES (Ext: 26922 or Bleep 2607 8.30am-17.00pm, out of hours please contact Consultant on call via switchboard).|
|Indication||Investigation of suspected poisoning. Mild initial clinical effects resemble alcohol intoxication.
|Additional Info||Methanol is directly toxic due to its suppressive effect on the central nervous system. Further toxic effects are exerted during metabolism as Methanol is converted by endogenous alcohol dehydrogenase to formaldehyde which is further completely metabolised by aldehyde dehydrogenase to formic acid.
The most important initial symptom of methanol poisoning is visual disturbance. As little as 4 mL methanol has been reported to cause blindness. However the usual dose reported to cause ocular toxicity in an adult is 30 mL, with 60 mL the usual minimum fatal dose. Formic acid can cause permanent blindness due to its toxicity to the optic nerve. Formic acid can cause a profound metabolic acidosis
Symptoms of visual disturbance may be delayed up to 24 hours after ingestion due to simultaneous alcohol administration and metabolic processes.
Therapy for methanol poisoning is aimed at blocking the action of alcohol dehydrogenase by administration of ethanol, which is the preferred substrate, or Fomepizole, a competitive inhibitor of the enzyme. Dialysis may also be required to remove methanol and its metabolites and to provide renal support.
Morbidity and mortality do not correlate directly with initial methanol concentrations; patient outcomes are significantly better for patients who are treated promptly. Samples for Methanol measurement should be collected before treatment is started and treatment should not be delayed pending a result.
Severe clinical effects are associated with concentrations > 500 mg/L although formate concentrations may be a better indicator of potential toxicity than methanol concentrations alone.
Symptoms are as follows:
30-120 mins post ingestion - clinical effects resemble those of mild ethanol inebriation with drowsiness, confusion and irritability.
After a latent phase of between 6-30 hours symptoms include dizziness, drowsiness, vomiting, severe abdominal pain and diarrhoea. In severe cases a marked anion gap acidosis will be present and tachypnoea is common as result. Coma and convulsions may also occur. Treatment requires nasogastric aspiration or gastric lavage.|
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|Ref. Range Notes||Methanol is usually absent from blood and urine|
|IP Acute TAT||Refer to Website|
|IP Routine TAT||Refer to Website|
|GP Acute TAT||Refer to Website|
|GP Routine TAT||Refer to Website|
Originally edited by : Eleanor McLaughlan. Last edited on 18/06/2020 13:41:41. Published By Matthew Clifford on 18/06/2019 13:41:41.