If an undead creature (like a Vampire) can benefit from drugs?

[S.Windhall]

1.Undead creatures automatically success the fortitude saves of the risk to becoming addicted to the drugs.
2.Undead creatures are immune to most drugs' negative effect, but can they benefit from their positive effect (normally some alchemical bonuses)?
3.If they can not, what can they benefit from? Potions? Alchemical items?

[Claxon]

The rules for drugs weren't created with players playing undead creatures in mind.

I'm not sure the rules handle it appropriately, and you should ask your GM.

If I was the GM, I wouldn't let you get something for nothing and would simply say undead are immune to drugs (both positive and negative effects).

[Saethori]

Don't do drugs, kids. Stick to more wholesome things, like being a bloodsucking abomination of the night.

I agree with Claxon's interpretation. If you have no functional bloodstream, drugs shouldn't have an effect.

[Quantum Steve]

The rules on drugs aren't very robust. They only work well when used as intended: normal PCs using them normally.
Try to throw in things like undead or offensive use, and they fall apart pretty quickly.