Aren’t there certain jobs (like Bus driver) where even if you have a legit 'script, you can’t be on that drug? 
Yes - because the underlying condition is held to be a safety risk.
For that matter, for bus drivers, train engineers, and pilots and lot of legal, over the counter drugs are forbidden while on the job due to safety concerns and require waiting periods of 8 or 12 hours to several days after the last dose taken before the person is legal to work again.
That’s a lot different than a desk job, though.