Laudanum was a drug.
Opium could be mixed with brandy to make laudanum. (PROSE: The Eight Doctors)
The Sixth Doctor had a pill that he picked up as a hangover cure from Zanthas IV which successfully counteracted the effects of laudanum in 1782. (AUDIO: Catch-1782)
Both Percy Shelley and Mary Shelley used laudanum, sometimes in large quantities. (AUDIO: Mary's Story, The Silver Turk)