. . been a concern?

Practically every contact Big Pharma has with health and medical professionals is a conflict of interest, from research to promotion to sales. You simply presume conflict of interest without fear of being wrong - it's the normal mode of operation.

If you wanted to prosecute this rigorously, you'd just have to shut down Big Pharma entirely. About all that can be done is jump on medical professionals when they step seriously out of line.