Poison Vector: Poison can be applied with a weapon, to a trap, to darts or needles, smeared in such a way as to seep in through the skin, or dispersed in a powder or gas so it’s inhaled. Poison in food or drink takes effect when it’s ingested unless otherwise noted. The poison attacks the victim when it makes contact through any of these means. Some poisons, as noted in their descriptions, can be administered only by specific means, such as in food or by a weapon that has been coated with the poison.
Poison Characteristics: Poisons are consumable items (similar to magic items). They affect you with an attack power. Some poisons have aftereffects, which apply after you save against the initial attack.
Poisoned Weapon Attacks: You must apply a poison to a weapon. The poison takes effect the next time the weapon hits and deals damage. The poison’s effect is a secondary attack against the same
target. If a poisoned weapon hits multiple targets, the poison attacks only the first target hit.
Apply a Poison: Apply poison to a weapon. This is a standard action. Poison applied to a weapon loses its potency at the end of the encounter or after 5 minutes have passed.
Published in Dungeon Master's Guide, page(s) 50.