Intoxicated

You’ll become intoxicated, if you drink too much at taverns.

Effects
How much each drink adds to your intoxication value is based on the creature’s constitution score, from 2 per drink at 24 con to 100 per drink at 1 con. The intoxication value decreases 1 every 12.5 seconds. The intoxicated icon shows up when the value reaches 50, and disappears when luck and morale modifiers reach zero, which is at value 49, ideally. The icon may stay an extra 150 seconds but the timer is still running in the background. It's possible the timer is influenced by haste or slow status (double or halve the timer), saving and loading may also reset the timer, because frequency-based timers are often cleared upon exiting game.
 * 0-49 intoxication: no bonuses or penalties
 * 50-59 intoxication: -2 luck and +2 morale
 * 60-69 intoxication: -4 luck and +4 morale
 * 70-79 intoxication: -6 luck and +6 morale
 * 80-89 intoxication: -8 luck and +8 morale
 * 90-99 intoxication: -10 luck and +10 morale
 * 100 intoxication (max): -12 luck and +12 morale

Causes
Outside of a tavern, some oddly murky bottles bestow 100 intoxication, it can also be one of the negative Wish spell results, which increases intoxication by 100 for 1200 seconds, and affects all creatures within 16 ft radius, bypassing magic resistance and offering no saving throws, but is dispellable. Party members may prevent it using Spell Immunity: Enchantment or Minor Globe of Invulnerability, as the “intoxication” spell a level 3 enchantment spell, just as some other side effect spells from Wish.

Cure
Cured naturally by spending time sober, resting, Slow Poison and Heal can also cure intoxication

Sources & references

 * semiticgod’s posts on BD forum
 * Special thanks to kjeron, for the extra info & clarifications regarding the topic