A member of the Sackler family, which owns OxyContin-maker Purdue Pharma, told people gathered at the prescription opioid painkiller’s launch party that the event would be “followed by a blizzard of prescriptions that will bury the competition”.

Top Purdue figurehead Richard Sackler made the comments in the mid-1990s, according to court documents filed on Tuesday afternoon in a case brought by the Massachusetts attorney general, Maura Healey. The case accuses the company and its executives of “deceiving” patients and doctors about the addictive and deadly risks of the groundbreaking narcotic pills.

In response, Purdue Pharma accused the attorney general’s office of cherry-picking from millions of emails and documents to create “biased and inaccurate characterizations” of the company and its executives. The company said it will “aggressively defend against these misleading allegations”.

Massachusetts is just one of thousands of jurisdictions that are currently suing Purdue Pharma and, in some cases, Sackler family members personally, for the devastating effects of OxyContin.

The state sued Purdue Pharma last June and named eight members of the Sackler family among a number of current and former executives and directors, alleging they misled the medical profession and the public about the dangers of OxyContin, the painkiller launched by Purdue in 1996 that is now at the center of an opioid epidemic that kills almost 200 people a day across the US.

“[OxyContin] became one of the deadliest drugs of all time,” the suit states. The case accuses the company of deceiving doctors and patients “to get more and more people on its dangerous drugs” and “misled them to use higher and more dangerous doses … At the top of Purdue, a small group of executives led the deception and pocketed millions of dollars,” the filing states.

The defendants deny the allegations and the case is ongoing. The next hearing in the case is on 25 January in Suffolk superior court in Boston.

Tuesday’s filing included newly unredacted information based on company records that has never been made public before, according to Healey.

Scientists in the federal government and inside Purdue warned Richard Sackler, then the senior vice-president of Purdue responsible for sales, of the risks that OxyContin would be abused if it was uncontrolled.

After a co-worker wrote to him with such a warning Sackler responded, according to Tuesday’s filing: “How substantially would it improve your sales?”

And at the OxyContin launch party, where the court filing says Sackler spoke of a “blizzard of prescriptions” for the potent painkiller, he added: “The prescription blizzard will be so deep, dense, and white.”

The plaintiffs commented in the filing: “Over the next 20 years, the Sacklers made Richard’s boast come true. They created a manmade disaster. Their blizzard of dangerous prescriptions buried children and parents and grandparents across Massachusetts, and the burials continue.”

In 1999, according to the latest filing, a Purdue employee reported to Richard Sackler that Purdue was making more than $20m a week in sales. OxyContin was its primary product. Richard Sackler replied that the sales were “not so great”. He continued: “Blah, humbug. Yawn. Where was I?” That same year, he became chief executive of Purdue Pharma and certain other family members named in the suit became vice-presidents.

“The company hired hundreds of sales representatives and taught them false claims to use to sell drugs,” the filing states, including misleading doctors on the risks of addiction and fatal overdose.

Parents whose children had died of OxyContin overdoses began writing to the company, with statements such as: “The only difference between heroin and OxyContin is that you can get OxyContin from a doctor,” according to the complaint.

And when a federal prosecutor wrote of 56 deaths in one state, Richard Sackler wrote in an email to Purdue executives: “This is not too bad. It could have been far worse.”

Then, the complaint says, Sackler began to stigmatize the victims of OxyContin addiction.

He wrote in a confidential email: “We have to hammer on the abusers in every way possible. They are the culprits and the problem. They are reckless criminals.”

The state responded in its suit that: “Richard followed that strategy for the rest of his career: collect millions from selling addictive drugs, and blame the terrible consequences on the people who became addicted.”

OxyContin’s main active ingredient, oxycodone, is a semisynthetic opioid originally derived from the opium poppy, and is more potent than heroin or morphine. It became dangerously overprescribed for chronic pain, despite its addictive properties.

OxyContin is a pain blocker and does not treat the underlying causes of the pain. It was found early on in the crisis, and still today, that such opioids can be addictive even as prescribed, and easily abused.

The next hearing in the Massachusetts case is on 25 January in Suffolk superior court in Boston.