The fear of designer drugs existed already in the 1980s. The comic strip Doonesbury even covered it - Uncle Duke hosted a designer drug conference in his 'medical university' in Haiti.
There already exist several ways to handle derivatives and analogues in drug prohibitions and restricted compound sales. Quoting from Wikipedia: "This then led the Health Committee of the League of Nations to pass several resolutions attempting to bring these new drugs under control, ultimately leading in 1930 to the first broad analogues provisions extending legal control to all esters of morphine, oxycodone, and hydromorphone."
There already exist several ways to handle derivatives and analogues in drug prohibitions and restricted compound sales. Quoting from Wikipedia: "This then led the Health Committee of the League of Nations to pass several resolutions attempting to bring these new drugs under control, ultimately leading in 1930 to the first broad analogues provisions extending legal control to all esters of morphine, oxycodone, and hydromorphone."