First formulated in the mid 1830s by Dr John B McMunn (or M'Munn); it became a big hit in the US once a drug company called A B Sands bought the recipe in 1841. The dosage instructions gave plenty of room for manoeuvre:

To a child a month old; or younger; give from half a drop to two drops; to a child 6 months old; from 3 to 10 drops; and to adults from 10 to 60 drops (or even double or treble that much; if the pain and other symptoms be severe and urgent) mixed in two or three teaspoonsfuls of water; according to the size of the dose. As the administration of every medicine should be governed by its effects; it is proper to begin with the smallest dose; and increase or repeat it at proper intervals until the desired effects are produced.

In 1864 the original recipe came to light; showing the process of treating opium with sulphuric ether to remove the narcotine and make the product safe - a nice idea but narcotine doesn't have narcotic properties anyway; and the medicine certainly was not safe. It was as addictive as any other opium product - in the early 20th century; for example; George Pettey M.D. related the case of a woman who had taken the Elixir for 31 years; losing 16 newborn babies to the congenital effects. Pictures From History