OxyContin maker Purdue Pharma has reached a tentative multibillion-dollar agreement with some plaintiffs aimed at settling thousands of lawsuits over its alleged role in the US opioid crisis. 

The settlement could be valued at up to $12 billion, they said, which would make it the largest such settlement in US pharmaceutical history. 

The following are some of the largest previous US legal settlements involving the pharmaceutical industry.

- Merck & Co - $4.85 billion in 2007 - Three years after it pulled its widely used arthritis pain drug Vioxx from the market over safety concerns and following several product liability trials, Merck agreed to pay nearly $5 billion to settle most of the 60,000 lawsuits alleging that Vioxx caused heart attacks and strokes. 

Kenneth Frazier, who was the company's general counsel and oversaw the litigation and settlement strategy, became Merck's CEO in 2011.

- American Home Products (Changed name to Wyeth) - $3.75 billion in 2000 - Three years after the weight-loss combination popularly known as fen-phen and used by millions of Americans was pulled from the market because one of the two drugs was linked to serious, potentially fatal heart valve problems, a federal judge approved a $3.75 billion class-action settlement. 

The agreement called for money to be distributed to those hurt by the drug, with payments of up to $1.5m depending on severity of injury or duration of use. The total included $1 billion set aside to pay for future medical checkups.

- GlaxoSmithKline - $3 billion in 2012 - GSK agreed to plead guilty and pay $3 billion in criminal and civil penalties for promoting drugs such as antidepressants Paxil and Wellbutrin for unapproved uses, failure to provide safety data for its Avandia diabetes drug and for paying kickbacks to doctors.

- Takeda Pharmaceutical - $2.4 billion in 2015 - The Japanese drugmaker agreed to pay $2.4 billion to settle thousands of lawsuits alleging that its Actos diabetes drug caused bladder cancer. Takeda did not admit liability and said the claims were without merit but agreed to settle to "reduce the uncertainties of complex litigation."

- Pfizer - $2.3 billion in 2009 - The settlement for improper marketing of 13 drugs included a $1.3 billion criminal fine for promoting the now-withdrawn arthritis pain drug Bextra for unapproved uses. The practices were exposed by six whistleblowers.

Pfizer had acquired Bextra with its purchase of Pharmacia. The case included off-label promotion of the anti-seizure drug Neurontin.

- Johnson & Johnson - $2.2 billion in 2013 - J&J agreed to the settlement to end civil and criminal investigations into promotion for unapproved uses of its antipsychotic drugs Risperdal and Invega and for paying kickbacks to pharmacists.

- Abbott Laboratories - $1.6 billion in 2012 - Settlement resolved civil and criminal allegations that Abbott promoted anti-seizure drug Depakote for uses not approved by US regulators. 

Abbott agreed to plead guilty to one misdemeanor violation of the Food, Drug and Cosmetic Act and enter into a Corporate Integrity Agreement with the US government to oversee its compliance programme for five years.

- Eli Lilly and Co - $1.42 billion in 2009 - The agreement settled criminal and civil charges that Lily promoted top-selling schizophrenia drug Zyprexa for unapproved uses and patients, including for children and the elderly. 

The resolution included a criminal fine of $515m and up to $800m in a civil settlement with the federal government and US states.