Food & Impairment
As previously discussed, having a meal just before drinking alcohol will result in a lower, delayed blood alcohol concentration peak (the point of greatest intoxication). Stated another way, if you eat before drinking alcoholic beverages, you will get less drunk and it will take you longer to get there. Remember, alcohol is absorbed much more efficiently in the small intestine than in the stomach, so if you drink alcoholic beverages on an empty stomach the alcohol passes through the stomach and into the small intestine quickly where absorption into the bloodstream happens with great efficiency. However, eating will slow the absorption of alcohol in the system because the alcohol will be trapped in the stomach with the food while the food is being digested. Although some absorption will take place while the alcohol is in the stomach, it is significantly less, and much slower, than it will be when the alcohol makes it to the small intestine. So, as long as the food is being digested and the pyloric valve stays closed, alcohol absorption will be comparatively slow.
The type of food ingested (carbohydrate, fat, protein) has not been definitively shown to have a measurable influence on the rate of absorption, but the larger the meal and closer in time the eating is to the drinking, the greater the reduction in peak alcohol concentration. Studies have shown reductions in peak alcohol concentration from 9% to 23% when following a meal as compared to drinking on an empty stomach.
Medication & Impairment
Many medications should not be combined with alcohol because they have a synergistic effect and significantly increase the intoxicating effect of the alcohol. It's one of those situations where the combined effect is larger than the two individual effects, or stated another way, 1 and 1 don't equal 2, they equal 3 or 4.
For example, you may be perfectly capable of driving safely on your medication, and you may be perfectly capable of driving safely after a glass of wine, but combining the medication with the glass of wine could leave you impaired and unable to drive a vehicle safely, even though your BAC may only be a 0.03. If you are taking any medication, always consult your physician and review the medical information which came with the medication before drinking alcohol while taking the medication.
Fatigue & Impairment
Common sense tells you that fatigue can cause many of the same symptoms caused by alcohol intoxication. More important, and the thing to be aware of, is the fact that the effect that a couple of drinks will have on you will be greater when combined with fatigue.