Opium has been a major item of trade for centuries, and widely used as a painkiller and sedative. Most patent medicine of the 19th century were based around laudanum (a solution of opium in alcohol). In the 19th century, the attempt by China to stop the British trade in opium from India was the cause of the Opium War which led to Britain acquiring Hong Kong.
see also [Opium Wars]?, opiates, [Thomas de Quincy]?, [Samuel Taylor Coleridge]?