Pharm 101: Ethanol



  • Multiple signalling pathways affected, mainly:
    • Enhances GABA action at GABA-A receptors
    • Inhibits NMDA receptors
  • Multiple organ system effects, mainly CNS depression, CVS depression and smooth muscle relaxation (see below)

  • Rapid absorption from GIT (water soluble), peak levels within 30 minutes
  • Rapid distribution, Vd approximates TBW ~0.5-0.7L/kg
  • Hepatic metabolism undergoes zero-order kinetics* with two major pathways to produce acetaldehyde:
    1. Alcohol dehydrogenase (ADH) pathway is primary pathway and forms NADH as co-product
    2. Microsomal ethanol-oxidising system (MEOS) pathway is induced in chronic alcohol consumption
  • Acetaldehyde is oxidised to acetate by enzyme ALDH, forms NADH as co-product. Disulfiram inhibits this reaction.
  • Excretion: lungs, liver
  • Induces CYP2E1 enzyme

*Elimination occurs at a constant rate independent of drug concentration. Other drugs that have zero order kinetic metabolism include aspirin, and phenytoin (at higher doses)

Clinical uses

Adverse effects
  • CNS depression:
    • Sedation and anxiolysis
    • Disinhibition, impaired judgment, impaired motor skills
    • Ataxia, slurred speech
    • Respiratory depression and coma
  • CVS depression:
    • Depression of myocardial contractility
  • Smooth muscle:
    • Vasodilation –> hypothermia
    • Uterine relaxation

Further reading

  • Katzung BG. Basic & Clinical Pharmacology. 14th ed. United States of America: McGraw-Hill Education; 2018. 396-404 p.

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MBBS (UWA) CCPU Emergency Medicine Advanced Trainee based in Melbourne, Australia. Co-author of the LITFL ECG Library. Likes Ultrasound, Echo, ECGs, and anything and everything with caffeine. Part of the 2021 ANZCEN Clinician Educator Incubator Programme | @rob_buttner | ECG Library |

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