Latency Period
Definition
The 12-24 hour window between methanol ingestion and onset of severe symptoms (visual disturbance, metabolic acidosis), during which the patient may appear to have recovered from mild inebriation. The latency reflects the time required for ADH to convert methanol to formaldehyde and then to formate at levels causing organ toxicity.
- Context
- Methanol poisoning
- Duration
- 12 to 24 hours
- Underlying cause
- ADH-mediated conversion to formaldehyde then formate
- Clinical danger
- Apparent recovery masks impending organ toxicity
Common questions
Why is the latency period clinically dangerous?+
A patient may feel only mild inebriation and appear to be recovering during this window, delaying treatment, while formate is silently accumulating and will produce severe visual disturbance and metabolic acidosis once it reaches toxic levels.
Does co-ingestion of ethanol change the latency period?+
Ethanol competes for the same alcohol dehydrogenase enzyme, which can slow methanol's conversion to its toxic metabolites and extend the apparent latency, a mechanism exploited therapeutically when ethanol or fomepizole is given as an antidote.
Related terms
- Alcohol Dehydrogenase (ADH)
- The hepatic enzyme (isoforms ADH1A, ADH1B, ADH1C) that catalyses the first oxidation step of both ethanol (to acetaldehyde) and methanol (to formaldehyde)...
- 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...
- 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...