Sure it might have an impact, but again the culpability of harm isn't on the consumer or advertiser. If people able to shop around for doctors to get any prescription then isn't that the problem, not the advertisement?
It doesn't matter if the adverts have an impact on sales, if it does then doctors are to blame, tv adverts cant prescribe people medication.
If we had heroin advertisements on TV showing how great life is while doing heroin, just ask your doctor, would you still say there is no culpability of harm on the company paying for the ads (the same company supplying all the heroin to the market)? And then remember, actually that was reality, they just didn't call it heroin.
If consumers didn't have in your face advertising about how this new magical wonderdrug will solve all your life problems and you'll be happy again just like all these paid actors, you think they'd still be shopping around doctors as hard? You think they'd even know to shop around for that wonderdrug or pressure their doctor to try it?
Do you think people's decisions to shop around for doctors has zero relation to the drug advertisements they see on TV, on billboards, on the side of busses, in magazines, on the radio, on websites, etc?
Do you think people would still buy as much Coca Cola if they stopped advertising?
With your logic we might as well allow marketing of tobacco to minors again. After all, stores aren't legally allowed to sell it to the minors, so it's just a fault of the stores and the kids.
Do you think we as a society are better off or worse off having pharmeceuticals directly advertised to consumers?
It doesn't matter if the adverts have an impact on sales, if it does then doctors are to blame, tv adverts cant prescribe people medication.