As a postcript , Drisgirl: You asked why an alcoholic could get drunk one one can of Special Brew.
In everyday terms (I'm no doctor!)when the condition is extremely advanced, and the liver shot,there may come a time when so little of it is functioning that the alcohol goes straight into the bloodstream very quickly: what's left of the liver isn't adequate to process it properly and slowly.So one drink suddenly produces the effect of a session.
Before that stage, alcoholics have an amazing capacity for alcohol, and extreme tolerance.Alcoholics drink a lot of alcohol without showing signs of drunkenness, and commonly pass as sober.An alcoholic can drink eight times what a sober person does in the same time and be no more affected than the sober person ,because their body is so tolerant and so good at processing the drink'
In fact, he or she, needs the drink to function every day, needs to have a certain level of alcohol just to act normally. I remember somebody saying to me "I'm sober today You don't what it's like,being a drunk" when at the time I'd already had at least three doubles and it was 9 am!.(We start early!) Someone who worked daily at our house said she never knew I drank until near the end, when she found me passed out on the floor!
So that's how it works.
Thanks for your kind comments.(It's been eight years sober now).