Very dangerous advice. Caffeine will counter some effects of alcohol, reinforce others, and have no effect at all on still other symptoms. In general, there are no two drugs, at all, with opposite effects.
For instance: Caffeine mixed with alcohol will decrease the sleepiness, it’ll increase the need to piss, and it won’t do a thing about the impaired vision. The decreased sleepiness is probably even a bad thing, since it’ll let you drink more before your body has the sense to call it quits.
mnemosyne said:
Is this what people mean when they speak of “empty calories” in booze?
“Empty calories” refers to calories in a substance essentially devoid of other significant nutrition.
I am surprised that neither Cecils article, linked above, nor posts here have mentioned the metabolism of methanol to formaldehyde and formic acid by the enzyme alcohol dehydrogenase.
The theory goes: this enzyme oxidises the ethanol to acetic acid which is then excreted. The same enzyme oxidises any methanol present (in low concs) into the formic acid, which leads to hangover symptoms.
By drinking more ethanol the hangover is avoided as the ethanol is preferentially metabolised and the methanol excreted without oxidation.
Some drinks with higher methanol content are worse.
So food grade ethanol may be good ‘hair of the dog’, but there are other factors at work such as dehydration, and toxicity of other oganics and their metabolites (including acetaldehyde).
Some asian groups lack the enzyme in the quantities of caucasians and are thus more greatly effected by EtOH.
A correction on my last point.
Just did a search and found this.
The enzyme variation in some asians is of the aldehyde dehydrogenase, which oxidises the aldehyde to the acid. Not the alcojol dehydrogenase.
A defective coding for this enzyme —> buildup of the aldehyde, thus leading to greater toxic symptoms than a functional ALDH2 enzyme.
I have heard this before, but I never understood it. What are these by-products or impurities, and how does distillation get rid of them?
Whoops… another side effect of responding to drinking posts while drunk 
Scoop More effective distillation removes congeners (such as other alcohols, aldehydes, esters and ketones). If distillation is discriminating enough you end up with pure ethanol instead of whiskey or grappa or arak.
Ethanol can be separated out by using a more efficient column or multiple distillations.
The reason for the separation of the congeners is that they have different boiling points to ethanol.
btw Dont discount the effect of dehydration, just removing the impurities wont remove all the hangover.