Vow of Decadance( Drow of the Underdark, p. 55)
You have taken an unspeakable vow to indulge your every desire, even at the expense of others around you.
Unspeakable Vow (DrU) ,
You cannot overdose when using drugs. If the drug deals variable damage, you always take the minimum amount. If the drug has a penalty that lasts for a variable amount of time, it is always for the minimum time described. In addition, you gain a +4 competence bonus on saving throws against ingested poisons
To fulfill your vow, you must consume an intoxicating, stimulating, depressing, or hallucinogenic substance at least once per day. If you intentionally abstain, you immediately and irrevocably lose the benefit of this feat. You may not take another feat to replace it. If you break your vow as a result of magical compulsion, or otherwise unintentionally, you lose the benefit of this feat until you perform a suitable penance and receive an atonement spell.