As far as I know the rule for ads is 'non prescription', beyond that it's hard.
I don't recall seeing an ad for a prescription drug in Canada in the last decade, though they might exist in some form.
We get American TV and those ads seem quite ridiculous, what with the senior citizens dancing away, and the narrator iterating through a huge list of symptoms, then listing off 30 or 40 side effects as fast as he can, as if people are remotely capable of understanding.
My family works in the drug industry, I should say one thing that people don't want to hear: a lot of doctors are lazy. Just because they're doctors, does not mean that they keep up in any way with current issues, trends. The level of power they have, and the relative lack of ongoing certification is ridiculous. Once they get their ticket, it's a golden ride for the rest of their lives if they want.
Many people complain about the 'free lunch' doctor's visits by the sales reps, but I don't see it as such a bad thing. It's intense and important information, I have no problem with Doctors getting a 'free ham sandwich' to entice them to go through the data on the latest trials.
Obviously, there are shenanigans there, misrepresentation, competitive issues, pricing etc. etc. - but frankly a 'highly moral sales/communication force' actually I think does add value - they get doctors to pay attention to the specific issues. Obviously, there are probably better alternatives ... but again, Doctor's guilds are very powerful and archaic, nobody can tell them what to do.