Heroin
From Tardis Wiki, the free Doctor Who reference
Heroin was an addictive psychoactive drug from Earth. The drug was synthesised from opium, and taken via hypodermic injection.
An alternate version of Samantha Jones was a heroin addict, desparate for her next fix. Fitz Kreiner talked her through the drug's harsh withdrawal symptoms. (EDA: Unnatural History)
Alun Griffiths and Julie Jones were heroin users. (TWN: SkyPoint)
Lucy was a heroin user. (TWN: Slow Decay)