By accepting SWAG from the pharma rep, or accepting free trips to conferences sponsored by pharma. If a doctor has not heard about a new drug the their reps just haven't made their way to them yet because they're in a smaller market. The yet is key, eventually a rep will make their way to them. More than likely much sooner than the TV ads run

By researching new drugs? Though sadly at the moment the doctor is also a target of advertising. The point being that this should generally be a pull process driven by a demand (and mediated by neutral review and publication processes) and not a push being driven by a supply (mediated by a process that goes to the highest bidder).

There are other ways of making information available

The role of search

so in your mind "advertisement" covers any transmission of information?

By doing their job instead of hoping a stranger's friend happens to land on a useful ad?