I know in one of the Sherlock Holmes stories, Watson lectures Holmes on the side effects of the morphine he's taking, and Holmes even concedes that it's a bad idea. Was this a popular view? If not, when did it start to become accepted that they were bad?
I actually want to ask a question on this topic too, if it is alright. What was the purity of 19th century morphine, heroin, etc.? Did manufacturers 'cut' drugs with other chemicals or substances like is the case with drugs (and in some rubbish pubs, alcohol with water) today?
In 1821 author Thomas de Quincey published Confessions of an English Opium Eater in the London Magazine. It details his long-term addiction to opium as well as his struggle to rid himself of said addiction. People who read this would have understood the addictive qualities of opium. I would recommend researching the reviews of de Quincey's work from that time, that should give you a bit of perspective as to how the British viewed the subject in the early 19th century. I highly recommend this book, it is a very interesting read!