Originally Posted by RNBSN
Superb observation. You've been doing your homework. Nonetheless, wouldn't recommend spending much time on half life considerations. It won't lead to individual predictability in elimination of EtG.
1) It isn't possible to determine how much EtG is produced in relation to a measured quantity of ethanol.
2) Metabolism (of ethanol) is genetically determined and standardly varies by a factor of 4x. The variation is attributed to the enzymes Alcohol Dehydrogenase (ADH) and Aldehyde Dehydrogenase (ALDH). Both of these enzymes are active in Phase I of ethanol metabolism. Both have genetic polymorphisms influencing individual variation
3) EtG results from late (Phase II) ethanol metabolism, dependent on Phase I, yet also subject to separate genetic influences, specifically polymorphisms controlling the production of UDP-glucuronosyltransferase (UGT), the microsomal enzyme responsible for the formation of EtG.
As a result, some people, regardless of metabolic rate, produce more EtG per given dose of ethanol than others. This variation is of enormous potential a variation of “200 fold”. One individual could have a low metabolic rate and at the same time be a “hyperproducer” of EtG.
4) Ethanol metabolism/elimination varies by dosage. That is one drink does not follow the same kinetic model as 10 drinks. At a certain point, seemingly tied to heavy and/or long term consumption, there is an additional metabolic system that kicks in, Microsomal Ethanol Oxidizing System (MEOS) [I call it liver overdrive]. This supposedly accelerates Phase I metabolism significantly. The interrelated inluence on EtG production (Phase II) has not, to my knowledge, been studied.
Combining the above, only very basic elements, any attempt to individually quantify EtG production/elimination by consumption/half life is, if not impossible, unproductive.
But please continue to read about EtG testing. The process needs close social and scientific scrutiny and your observations are correct: The facts don't comport with the conclusions.
Nonetheless, in more direct response to your question, I note that we have a couple of members academically qualified to address your more direct query in relation to interpreting half life: See DrBob1
and Unknown008 https://www.askmehelpdesk.com/members/unknown008.html
I believe, as commonly applied, it is an inadequate model for alcohol metabolism. But, please, decide for yourself.
Should you need additional resources or references for EtG please let me know.