Mrs. Charlotte N. Winslow started making her infamous Soothing Syrup sometime in the mid-1800s. Designed primarily for teething babies, and as a general cure-all for infants, it was advertised as "The Mother's Best Friend", but eventually got the reputation, and the name of "Baby killer". The lethal concoction contained some ingredients, that even in the mid to late 1800s, should have rung some alarm bells among parents, who must have been utterly ignorant to have given it to their babies.
The syrup was widely sold both in the UK and the United States. It wasn't until 1911, when the American Medical Association published a book, naming and shaming quack remedies and snake-oils. In a section called "Baby Killers", Mrs. Winslow and her syrup were rightly named and shamed. However, the syrup remained on sale in the UK until 1930. Which means that the parents were still spoon feeding this laudanum for kids, to their children, long after the dangers of opium and alcohol being mixed, were considered dangerous for adults.