Retcon

Retcon was a pill that would induce amnesia in anyone that took it. It was used by Torchwood 3 to keep secret its operations from civilians. A side-effect of the pill was induced unconsciousness.

Other information

 * Retcon appears capable of only erasing selective memories, or allowing the implantation of false memories. When given to the wedding party following alien disruption of the wedding of Gwen Cooper and Rhys Williams, it did not result in a large group of people forgetting that Gwen and Rhys were married. (TW: Something Borrowed)
 * Irving Braxiatel had access to a similar drug which caused a person (particularly a human) to lose the last 24 hours of their memory. (MA: The Empire of Glass)