Diamorphine

Diamorphine was a drug that Gwen Cooper acquired from a pharmacy she'd robbed. She and her mother Mary used the drug on her father Geraint, Mary noting that "this won't last a week the way he's going through it."

It was an illegal drug that Gwen used to arrest people for possessing — "It's practically heroin." (TV: The Gathering)

In the early 21st century, diamorphine was legal in the United States. (PROSE: Cat's Cradle: Warhead)

In an alternate timeline, Sam Jones used diamorphine. (PROSE: Alien Bodies)