Pharm 101: Methanol

Class

Toxic alcohol

Metabolism

• Three-step process
• Methanol –> formaldehyde (alcohol dehydrogenase)
• Formaldehyde –> formic acid (aldehyde dehydrogenase)
• Formate –> CO2 and H2O (folate-dependent pathway)

Methanol poisoning

• CNS depression similiar to alcohol overdose
• Metabolite formic acid causes:
  • Severe metabolic acidosis
  • Blindness
  • Coma

Treatment of methanol poisoning

• Metabolism of methanol to formic acid can be blocked by inhibiting enzyme alcohol dehydrogenase with competing drug fomepizole (4-methylpyrazole). IV ethanol is also an effective antidote
• Enhanced elimination via haemodialysis
• Alkalinisation to counteract metabolic acidosis (with bicarbonate)
• Folate and folic acid are often administered, as folate-dependent system is responsible for oxidation of formic acid to CO2

Further reading

• Buttner R. Pharm 101: Ethanol

References

• Katzung BG. Basic & Clinical Pharmacology. 14th ed. United States of America: McGraw-Hill Education; 2018. 405-406, 1041, 1045 p.