Purdue Pharma and three current and former senior executives have pleaded guilty to charges that the firm deliberately misled the US public about the risk of addiction associated with its painkiller Oxycontin.

The company has entered a guilty plea in a US district court in Virginia to a felony charge of misbranding OxyContin (extended-release oxycodone), thus ending a four-year investigation by the US Attorney’s Office. Under the terms of the settlement, Purdue will pay $470 million to government agencies and $130 million to resolve private civil liabilities related to painkiller.

It has also entered into a ‘non-prosecution’ agreement calling for the firm to maintain a compliance programme and allow for an independent review of its practices for a 60-month period. In addition, the company's president Michael Friedman and chief legal officer Howard Udell will pay fines totalling $19 million and $8 million, respectively, while Paul Goldenheim, Purdue’s former head of R&D, is being hit with a $7.5 million penalty. However the company was quick to point out that the three men “neither engaged in nor tolerated the misconduct at issue in this investigation”.

The problems started “nearly six years and longer ago,” according to Purdue, “when some employees made, or told other employees to make, certain statements about OxyContin to some healthcare professionals” that were inconsistent with US Food and Drug Administration-approved prescribing information “and the express warnings it contained about risks associated with the medicine.” These include addiction, abuse, withdrawal, and tolerance compared to other painkillers and Purdue said that “we accept responsibility for those past misstatements and regret that they were made”. The firm added during the past six years, we have implemented changes to our internal training, compliance and monitoring systems that seek to assure that similar events do not occur again”.

US Attorney John Brownlee said that with OxyContin, the company “unleashed a highly abusable, addictive, and potentially dangerous drug on an unsuspecting and unknowing public," and for “ these misrepresentations and crimes, Purdue and its executives have been brought to justice. From 1996 to 2001, the number of oxycodone-related deaths nationwide increased five-fold while the annual number of OxyContin prescriptions increased by nearly 20 times. In 2002, it caused 146 deaths and contributed to another 318 as drug abusers learnt to defeat the time-release properties of long-acting opioid analgesics by snorting or injecting them to achieve their highs.

Purdue has now acknowledged that it illegally promoted OxyContin by falsely claiming that it was “less addictive, less subject to abuse and diversion, and less likely to cause withdrawal symptoms than other pain medications – all in an effort to maximise its profits," concluded Attorney Brownlee.

The guilty plea ended a bad week for Purdue which had earlier agreed to pay a total of $19.5 million to 26 US states and the District of Columbia to settle allegations that it marketed OxyContin for off-label uses and failed to adequately warn physicians or patients of the potential risks for abuse and addiction.