The state of Massachusetts sued a subsidiary of the French public relations firm Publicis on Thursday for its role promoting opioids in what became a major US health crisis.

That subsidiary, Publicis Health, is accused of helping Purdue Pharma urge doctors to prescribe its highly addictive painkiller OxyContin.

The lawsuit alleges that Publicis "engaged in myriad unfair and deceptive strategies that influenced OxyContin prescribing across the nation," a statement by Massachusetts Attorney General Maura Healey's office said.

Those strategies were carried out through dozens of contracts between 2010 and 2019, worth more than $50 million, it stated.

Tactics included combatting doctors' "hesitancy" to prescribe the medication, and persuading them to prescribe OxyContin over lower-dose, short-acting opioids, thus increasing the risk of addiction.

Massachusetts is asking that Publicis Health pay "compensatory damages" of an unspecified amount for having "created a public nuisance."

In a statement, a spokesperson for Publicis Health said that "all of our work was completely lawful," and that the events in the lawsuit fall outside the statute of limitations.

Before the Covid-19 pandemic the opioid crisis seemed to be leveling off, but the death toll from overdoses began to climb again in 2020
Before the Covid-19 pandemic the opioid crisis seemed to be leveling off, but the death toll from overdoses began to climb again in 2020 US Drug Enforcement Administration / Handout

"Publicis Health acted solely as an advertising agency," the spokesperson said, adding that "our role was limited to implementing Purdue's advertising plan and buying media space."

US states has sued Purdue -- which filed for bankruptcy in 2019 -- as well as many other entities believed to be co-responsible for the devastation caused by the opioid crisis.

These include global consulting firm McKinsey and the wealthy Sackler family, which founded Purdue.

A trial meanwhile opened Monday in West Virginia, one of the states most devastated by the opioid epidemic, against leading pharmaceutical makers and distributors.

Before the Covid-19 pandemic, the crisis seemed to be leveling off after nearly 500,000 Americans died from overdoses involving prescription and illicit opioids from 1999 to 2019, according to the Centers for Disease Control and Prevention.

But the death toll from overdoses began to climb again in 2020, reaching a record high of more than 87,000 fatalities from September 2019 to September 2020, according to federal figures released in April.

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