There likely isn't anyone who would disagree that substance abuse of any kind has a deleterious effect on people. You don't function with as much clarity and speed when you are impaired by drugs or alcohol. That's why random drug testing is becoming so common in so many areas of society. Pro and college athletes face such tests. So do students in many high schools and colleges.
One industry in which mandatory random drug testing is not generally in use is the medical profession. It may be something that is practiced by some large scale health care service companies, but it's not something applied to all practitioners in Missouri or any other state.