In the 19th century, laudanum was used in many patent medicines to "relieve pain... to produce sleep... to allay irritation... to check excessive secretions... to support the system... [and] as a sudorific". The lack of any genuine treatments meant that opium derivatives were one of the few substances that had any effect, and so laudanum was prescibed for ailments from colds to meningitis to cardiac diseases in both adults and children.
The Victorian era was marked by the widespread use and abuse of laudanum in England, Europe and the United States. Initially a working class drug (it was cheaper than a bottle of gin or wine, because it was treated as a medication for legal purposes, not taxed as an alcoholic beverage); it gained wider popularity, including among literary figures (de Quincey, Byron, Shelley, Coleridge, and Dickens) and politicians (Wilberforce).
See also: paregoric.