Oh absolutely. Trust me I know. It is actually the primary way lots of doctors get info on new drugs. And they will start giving out those sample almost immediately upon recieving them
I used to run the pharmacy of a veterinary clinic when I worked as a vet tech. Same thing. Well, not really the same thing in terms of big business. But I had to deal with drug reps on a daily basis. And sometimes it was a good thing. I mean, sometimes there were some products that I actually pushed for that turned out to be really good. But we were careful to really do our research and no what we were putting out.
Should a doctor be depending on a "salesman" as his primary source of info on new drugs? Hell, no.
And on the subject of side-effects it is true that many of the milder side effects from many drugs are temporary. Just an initial reaction that goes away after a week or two.