Alcohol Dehydrogenase (ADH)
Definition
The hepatic enzyme (isoforms ADH1A, ADH1B, ADH1C) that catalyses the first oxidation step of both ethanol (to acetaldehyde) and methanol (to formaldehyde) using NAD+ as cofactor. Competitive inhibition of ADH by ethanol or fomepizole is the basis of methanol antidote therapy.
- Location
- Liver
- Isoforms
- ADH1A, ADH1B, ADH1C
- Cofactor
- NAD+
- Ethanol product
- Acetaldehyde
- Methanol product
- Formaldehyde
Common questions
Why does ethanol act as an antidote for methanol poisoning?+
Ethanol competes with methanol for the same ADH active site and binds it preferentially, so administering ethanol slows the conversion of methanol into its toxic metabolites formaldehyde and formic acid, buying time for methanol to be cleared or dialysed unchanged.
Why is fomepizole often preferred over ethanol for methanol poisoning treatment?+
Fomepizole inhibits ADH directly without the sedation, variable dosing, and monitoring difficulties that come with using ethanol itself as the competing substrate, giving more predictable blockade of methanol metabolism in clinical practice.
Related terms
- Anion-Gap Metabolic Acidosis
- The metabolic acid-base disorder produced by accumulating formate in methanol poisoning. The anion gap (Na+ - [Cl- + HCO3-], normal 8-12 mEq/L)...
- Congener Fingerprinting
- The use of the full volatile congener profile (fusel alcohols, acetaldehyde, ethyl acetate, pyridine, MIBK) in illicit liquor samples to establish batch...
- Fomepizole (4-Methylpyrazole)
- A specific competitive inhibitor of alcohol dehydrogenase (Ki approximately 0.1 µM), used as the preferred antidote for methanol poisoning in high-resource settings....
- Formate (Formic Acid)
- The terminal toxic metabolite of methanol oxidation (HCOO-, pKa 3.7). Formate inhibits cytochrome c oxidase (mitochondrial complex IV), causing optic nerve and...
- FSSAI Methanol Limit
- Under India's Food Safety and Standards (Alcoholic Beverages) Regulations 2018, the maximum methanol content permitted in legally produced and sold spirits is...
- Haemodialysis in Methanol Poisoning
- The most efficient treatment for removing both methanol and formate from circulation and correcting severe metabolic acidosis. The EXTRIP workgroup (US) and...
- Latency Period
- The 12-24 hour window between methanol ingestion and onset of severe symptoms (visual disturbance, metabolic acidosis), during which the patient may appear...
- Pyridine
- An aromatic nitrogen heterocycle used as a secondary denaturant in Indian denatured spirit formulations (at 1-2% v/v). Its presence in a headspace...
- Vitreous Humour
- The gel-filled interior of the eye, anatomically isolated from hepatic and gastric post-mortem redistribution sources. In forensic toxicology of hooch deaths, vitreous...