(Adds further details on lawsuit)
Aug 8 (Reuters) - New Hampshire sued OxyContin maker Purdue Pharma LP on Tuesday, becoming the latest state or local government to accuse the drugmaker of engaging in deceptive marketing practices that have helped fuel a national opioid addiction epidemic.
The lawsuit filed in Merrimack County Superior Court claimed that Purdue Pharma significantly downplayed the risk of addiction posed by OxyContin and engaged in marketing practices that "opened the floodgates" to opioid use and abuse.
The complaint said the Stamford, Connecticut-based company spent hundreds of millions of dollars since the 1990s on misleading marketing that has also overstated the benefits of opioids for treating chronic, rather than short-term, pain.
Purdue and three of its executives in 2007 pleaded guilty to federal charges related to the misbranding of OxyContin and agreed to pay a collective $634.5 million to resolve a U.S. Justice Department probe.
That same year, the privately-held company reached a $19.5 million settlement with 26 states and the District of Columbia.
Yet the lawsuit by New Hampshire, which was not among those who settled, said Purdue has continued to benefit from its earlier misconduct and has since 2011 maintained and expanded the market for opioids in the state.
"New Hampshire continues to experience a severe opioid epidemic," Deputy Attorney General Ann Rice said in a statement. "Last year alone nearly 500 overdose deaths occurred - almost ten times more than in 2000."
Purdue in a statement said that while it denies the allegations, "we share New Hampshire officials' concerns about the opioid crisis and we are committed to working collaboratively to find solutions."
The lawsuit followed similar cases against Purdue and other drugmakers by states including Oklahoma, Mississippi, Ohio and Missouri and several cities and counties in California, Illinois, Ohio, Oregon, Tennessee and New York.
A group of state attorneys general announced an investigation in June of the role played by pharmaceutical companies in the opioid epidemic. (Reporting by Nate Raymond in Boston; Editing by Chris Reese)