The only official rules for alcohol intoxication I know of are from the D&D Arms and Equipment Guide. The rules translate to d20 Modern seamlessly, in a nutshell here they are:
Wine DC 11 or 12
Ale/Beer DC 10 to 13 (weak to very strong)
Spirits DC 11 to 15 (typical liquor to dangerously strong)
You make a fort save for each drink. The first drink consumed within an hour has no additional penalty, but each additional drink imposes cumulative penalties that double (-1, -2, -4 and so on to the saves). You can fail the save voluntarily.
On a failed save you take a 1d2 penalty to both Wisdom and Dexterity. If your WIS reaches 0 you pass out, if your DEX reaches 0 you're a drunken wreck who can't move but you're still conscious. If both reach 0 you can suffer alcohol poisoning. If you're in danger of Alcohol Poisoning you have to make a save with the DC of the strongest liquor you consumed, on a failure you take 1 point of CON damage per 10 minutes until the stomach is purged.
The WIS and DEX penalties disappear at a rate of 1 point per hour after you stop drinking. Neutralize Poison eliminates the penalties instantly, but not any feeling of a hangover (no game mechanic for hangovers, just roleplaying, but if you're dealing with big penalties you'll probably have one).