Minnesota is suing Purdue Pharma, the manufacturer of the narcotic painkiller OxyContin, following a prolonged investigation into its marketing and other tactics that allegedly contributed to a rising number of patient addictions and overdose deaths.

The lawsuit, filed Monday by state Attorney General Lori Swanson in Hennepin County District Court, seeks to recoup money lost by Minnesota taxpayers in paying for opioid painkillers for unproven and harmful purposes. Modeled after successful efforts to sue tobacco companies for the harm cigarettes caused, Swanson said she hopes to gain money from Purdue to fund addiction treatment.

"This company misrepresented and minimized the addictive nature of its drugs in order to sell more of them," she said Monday at a news conference in St. Paul.

Swanson accused the pharmaceutical company of launching or promoting research suggesting that OxyContin was not addictive, bankrolling organizations to promote that message, falsely claiming that the drug worked for 12 hours and had no dose limit, and blaming patients rather than the drug itself for their addictions.

Deaths linked to legal opioid painkillers such as OxyContin, and illicit forms such as heroin, increased in Minnesota from 54 in 2000 to 401 in 2017, according to the Minnesota Department of Health.

A Purdue statement criticized Swanson for filing suit and pursuing a "costly and protracted litigation process" amid ongoing negotiations with multiple states, including Minnesota, in federal court.

"We will continue to work collaboratively with the states toward bringing meaningful solutions to help address this public health crisis," the Purdue statement said.

Swanson, a DFL candidate for governor, said she filed the lawsuit because she was unhappy with the pace of negotiations in federal court.

Minnesota's prescribing rate of opioid painkillers has been among the lowest in the nation, and it has declined in recent years through a variety of efforts, including the state Board of Pharmacy's monitoring activities to identify addicts who were "doctor shopping" for prescriptions, and doctors who were overprescribing to their patients.

But an epidemic started by prescription painkillers has morphed into one fueled by illicit heroin, and by legal and illegal forms of fentanyl — a powerful synthetic that was implicated in the overdose death of pop star Prince. The number of opioid-related fatalities increased in 2017, even though deaths linked to common painkillers declined, because deaths linked to fentanyl and related synthetics increased from 99 in 2016 to 172 last year.

A review of Minnesota death records by the Star Tribune found 27 deaths in 2017 linked to carfentanil, which is 100 times more powerful than fentanyl and is commonly used as an elephant tranquilizer. The state had only reported one prior death from this drug, which can come in a powder form that is hazardous to the touch for police and first-responders when treating overdose victims.

Law enforcement officials in Minnesota have been seeking to intensify prosecutions of drug dealers who distribute drugs containing fentanyl and related synthetics — and in some cases to charge dealers with homicide.

Swanson said it remains critical to hold legitimate manufacturers accountable. Her office also sued drugmaker Insys for high-pressure sales tactics to get doctors to prescribe a fentanyl spray at high doses and for questionable purposes. She said more state lawsuits against opioid manufacturers are being considered.

The attorney general said the Purdue lawsuit will be more complicated than cases against tobacco companies, because of the burden of proving that initial addictions to prescription opioids were related to the addictions and deaths of people from illicit substances.

Purdue has faced a series of lawsuits over the past decade, settling in 2007 a suit by 27 states (not including Minnesota) for its marketing of OxyContin, and pleading guilty in New York to misleading the public and paying more than $600 million in fines.

Jeremy Olson • 612-673-7744