You do not need the Alchemy Skill to drink an elixir or feed one to someone else. The Herbal Lore Skill allows you to apply coatings (to surfaces or Weapons as appropriate). Three levels of the Alchemy Skill allow you to use Alchemy Globes (usually thrown).

Alchemical substances will have no effect on certain creatures such as Undead or Constructs. If the creature does not have a metabolism, or has an alien metabolism, Alchemy poisons will likely not work. Creatures will call “no effect” if that is the case.

Some Alchemy can be reversed by a specific antidote if taken after exposure to it.

The spell defensive Poison Shield will not stop ingested substances from taking effect, but will stop all other attacks with the Poison qualifier such as Alchemy Globes. The species Skill Resist Poison may be used on any effect with the Poison qualifier no matter how it is delivered and is one of the only ways to stop an ingested toxin.

Note that coatings which do not affect the metabolism (e.g. do not use the Poison qualifier) are not stopped by a Poison Shield and can only be removed by an appropriate cure—in some cases an Alchemical Solvent, in others a Purify or a Dispel.

You cannot have more than one active coating on your Weapon or any other item at any one time, and only the most recently applied will be effective. There are Rituals that may circumvent this rule.