The problem of off-label marketing of medicines is common in US and appear to be the most difficult to control external regulatory approaches.

All of the whistleblowers alleged prescriber-related practices (including providing financial incentives and free samples to physicians), and most alleged internal practices intended to bolster off-label marketing, such as sales quotas that could only be met if the manufacturer's sales representatives promoted off-label drug use. Payer-related practices (for example, discussions with prescribers about ways to ensure insurance reimbursement for off-label prescriptions) and consumer-related practices (most commonly, the review of confidential patient charts to identify consumers who could be off-label users) were also alleged. However, these practices were alleged by whistleblowers in cases intervened by the US Department of Justice, and were not the subject of testimony in a full trial; thus, some of the practices identified by the researchers could not be confirmed.
The authors say: "Off-label marketing has been ubiquitous in the health care system and features some behaviors and strategies that may be resistant to external regulatory approaches."
They continue: "Aside from sales representatives and other company insiders, who play important roles as whistleblowers, physicians are alone in having a full view of many of the most insidious forms of illegal marketing outlined in the complaints we reviewed. As physicians' understanding of these practices and the consequences of inappropriate off-label promotion for public health evolves, so may their enthusiasm for shutting them down."
Source-Eurekalert