What about the first amendment?
https://en.wikipedia.org/wiki/Fairness_Doctrine#Decisions_of...
Free Speech doesn't really factor into a huge portion of what you see from the FDA, FTC, SEC, CFPB, and hundreds of state-level organs focused on regulating deceptive business practices.
One solution for restricting advertising would be to allow consumers to sue drug companies for false claims or for misinforming doctors.