In response to PanPanYourself, the problem at altitude is that the affinity between haemoglobin and alcohol is higher than that between haemoglobin and oxygen, so alcohol and altitude are a poor mixture and can exacerbate altitude sickness problems as you suffer from a proportionately lower level of oxygen in your bloodstream than you would sober at the same altitude. I used to work regularly at 14000' (Mauna Kea) and would avoid alcohol for at least 9 hours before going to the summit.