Carfentanyl
From Tardis Wiki, the free Doctor Who reference
Carfentanyl was a drug used as an anaesthetic and a sedative.
It had a quantitative potency approximately ten thousand times that of morphine. It was usually used to sedate very large animals.
Originally intending to use it on Weevils, Owen Harper used a pressurised air syringe full of carfentanyl on Marianne Till. It wasn't enough to subdue her, so he gave her a further dose of Ketamine. (PROSE: Slow Decay)
