A one-dose vial of this potion can be found on the floor of a worn-down house in the small goblin settlement north-east of the Observatory, south of Greasycheeks, Smellytoes, and Creakyknees. It respawns once every 49 seconds.
Since 7 February2012 players will get a warning in their chatbox when the potion is about to wear off: "Your resistance to poison is about to expire". Then they will get another message when it has worn off, approximately 15 seconds after the initial warning: "Your resistance to poison has expired". This allows you to keep track of how long you have until you have to drink again.