If you are trying to understand drug control, it is a presentist mistake to begin with opium. (presentism is the fallacy of judging or viewing the past through values and ideas of the present, rather than understanding them in their historical context.)
Although many national and international agreements signed at the beginning of the 20th century focused on opium as a problematic substance, it is worth asking how we got to the point where governments thought legislative action against the sale and purchase of a substance was necessary. That may seem weird, since we have all sorts of laws prohibiting or severely restricting the importation or manufacture of substances (especially mind altering ones). But those laws, like all laws, were developed at a moment when they were viable, and possible. Prior to that, it might not have been pragmatic or even seen to be the role of the government to place such restrictions on individual purchase or manufacture of products.
There is enough material out there on this that I don’t need to cover it. Laissez-faire economics was the principle that governments did as little as possible to interfere with the operation of the market. Liberalism as a governing philosophy insisted that governments had a strictly limited role in controlling the actions of individuals. If an individual’s actions were not hurting anyone else, it was not the role of government to legislate against that action (it was a major argument against the prohibition of liquor, and can be found especially in the writing of liberal philosopher John Stuart Mill, notably in On Liberty)
Nevertheless, governments were being encouraged to restrict trade on products that might do damage to individuals. Most notable were poisons, or products that could kill. The development of professional pharmacy was based at least partly on arguments that a responsible and respectable vendor needed to be the one in control of the sale of dangerous drugs. Substances like strychnine, arsenic, and opium, all valid medicines, could also kill in high doses (there were many more but these are the ones you’ll see most often talked about). Stories of people being intntionally or unintentionally poisoned often caught the macabre attention of newspaper readers.
One problem came from the fact that these products were not exclusively medicinal in nature. Arsenic, for example, was used in insecticides. The most notorious form was “Paris green” (also called Vienna Green, Schweinfurt Green, and Emerald Green). this was an arsenic based insecticide that would be sprayed or misted over the leaves of plants to keep insects from eating them. It was highly effective, and in demand. But it was a green powder. It might look tasty to unsuspecting eyes. And was lethal.
The misuse of products like Paris green and other items that were highly valuable but also lethal (rat poisons, opiates for sleep or pain killing, etc) provided a key justification for the development of pragmatic restrictions on drugs.
Here is an article on an investigation into arsenic poisoning in England.
Here is a story of a trial of a physician in Brighton, Canada West, accused of poisoning with arsenic.
Along with that, many prescriptions written by doctors were recipes that needed a skilled pharmacists to compound (some of the banner images for this site include such recipes).
Here is a recipe from Pingle’s drug store, Medicine Hat Alberta.
These would be sold in packages that the patient/customer had to mix with a solvent like alcohol or water and drink. Unlike prepackaged pills with set doses, prescriptions like this benefited from the skill of a pharmacist who knew how to measure potency, how to store drugs that might lose potency, and how to properly combine them (some drugs reacted poorly when mixed, but physicians might not know that). These skills, pharmacists argued, were important for protecting the public, needed to be developed through years of education and training, and should be protected by professional closure (so called because entry to the profession was “closed”, limited to those who could demonstrate their skill, through examination or other process of validation, to a body of similarly trained pharmacists).
Here is another prescription from Pingle’s Drug and Book Company in Medicine Hat Alberta, this one includes “Liq Arsenicalis.” As with many prescriptions, the condition is unstated.
So the dangers of death by misuse of certain drugs, and the need for properly compounded medicines, were the bases upon which was built the rationale for governments to restrict substances considered “dangerous.” With that precedent set, it was not much of a stretch to redefine “dangerous” to mean something less than lethal, for example something that caused a dependency. As to the question of why dependency was considered a problem, you can read up on that yourself.
(c) 2020 Dan Malleck
Note. Prescriptions held in the Pingle Drug and Book Company fonds at the Medicine Hat Archives, in the Esplanade Building, Medicine Hat, Alberta, Canada. Photos were take in 2015. Files over 100 years old are open, and photos are reproduced without patient names to protect patient identities.