- TIME COURSE: Adverse health effects from methanol poisoning may not become apparent until after an asymptomatic period of 1 to 72 hours.
- EFFECTS OF SHORT-TERM (LESS THAN 8-HOURS) EXPOSURE: Methanol’s toxicity is due to its metabolic products. The by-products of methanol metabolism cause an accumulation of acid in the blood (metabolic acidosis), blindness, and death. Initial adverse health effects due to methanol poisoning include drowsiness, a reduced level of consciousness (CNS depression), confusion, headache, dizziness, and the inability to coordinate muscle movement (ataxia). Other adverse health effects may include nausea, vomiting (emesis), and heart and respiratory (cardiopulmonary) failure. Prognosis is poor in patient/victims with coma or seizure and severe metabolic acidosis (pH <7). Early on after methanol exposure, there may be a relative absence of adverse health effects. This does not imply insignificant toxicity. Methanol toxicity worsens as the degree of metabolic acidosis increases, and thus, becomes more severe as the time between exposure and treatment increases.
- EYE EXPOSURE:
- Irritation, redness, and pain.
- INGESTION EXPOSURE:
- Ingestion of methanol may cause a wide range of adverse health effects:
- Neurological: headache, dizziness, agitation, acute mania, amnesia, decreased level of consciousness including coma, and seizure.
- Gastrointestinal: Nausea, vomiting, lack of an appetite (anorexia), severe abdominal pain, gastrointestinal bleeding (hemorrhage), diarrhea, liver function abnormalities, and inflammation of the pancreas (pancreatitis).
- Ophthalmologic: visual disturbances, blurred vision, sensitivity to light (photophobia), visual hallucinations (misty vision, skin over the eyes, snowstorm, dancing spots, flashes), partial to total loss of vision, and rarely eye pain. Visual examination may reveal abnormal findings. Fixed dilated pupils are a sign of severe exposure to methanol.
- Other: Electrolyte imbalances. Kidney failure, blood in the urine (hematuria), and muscle death at the cellular level (rhabdomyolysis) have been reported in severe poisonings. Fatal cases often present with fast heart rate (tachycardia) or slow heart rate (bradycardia) and an increased rate of respiration. Low blood pressure (hypotension) and respiratory arrest occur when death is imminent.
- SKIN EXPOSURE:
- Irritation.
- See Ingestion Exposure.
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