It is the first settlement to result from a wave of recent lawsuits over the drugmaker's marketing of painkillers.

The settlement with Oklahoma Attorney General Mike Hunter came just weeks before Purdue, owned by members of the wealthy Sackler family, was set to face the first trial to result from around 2000 lawsuits nationally against opioid manufacturers.

Oklahoma's top court declined to delay the landmark trial set for May in a multibillion-dollar lawsuit accusing Purdue and two other drugmakers of helping fuel an opioid abuse and overdose epidemic in the state.

Hunter's 2017 lawsuit accuses Purdue, Johnson & Johnson and Teva Pharmaceutical Industries Ltd of engaging in deceptive marketing that downplayed the risks of addiction associated with opioid pain drugs while overstating their benefits.

The companies deny wrongdoing. They had sought to delay the May 28 trial to September 16, citing the need to review records the state belatedly turned over that could be critical to their defence. The state is seeking over $US20 billion ($A28 billion) in damages.

The trial delay bid came as Purdue, owned by members of the wealthy Sackler family, was exploring filing for Chapter 11 bankruptcy protection to address potential liabilities stemming from the lawsuits, people familiar with the matter have told Reuters.

Opioids, including prescription painkillers, heroin and fentanyl, were involved in a record 47,600 overdose deaths in 2017, according to the US Centers for Disease Control and Prevention.

The epidemic has prompted lawsuits by state and local governments accusing Purdue and other drugmakers of contributing to the crisis.

Australian Associated Press