One of the world’s biggest drug companies, Johnson & Johnson, has gone on trial accused of fuelling the opioid epidemic that has claimed thousands of lives in the US.

Prosecutors in Oklahoma accuse Johnson & Johnson – probably best known for its baby shampoo and baby powder – and subsidiary Janssen Pharmaceuticals of deceptively marketing painkillers and downplaying addiction risks.

Oklahoma attorney-general Mike Hunter said Johnson & Johnson and Janssen Pharmaceuticals, which produced an opioid patch and pill, created a public health crisis that killed 4653 Oklahoma residents between 2007-2017.

The US Centres for Disease Control and Prevention says 46 people die every day in America from overdoses involving prescription opioids.

In 2017, prescription opioid drugs were said to be involved in more than 35 per cent of 47,600 opioid-related overdose deaths in the US.

Johnson & Johnson has denied any wrongdoing.

Oklahoma attorney-general Mike Hunter in court. Photo: AAP

The case, which started in city of Norman on Tuesday (US time), makes Oklahoma the first US state to take a major pharmaceutical company to trial over the epidemic of deaths from prescription opioid overdoses.

In his opening statement, Mr Hunter said Johnson & Johnson disregarded the dangers related to opioid abuse in marketing its products and created an it was time to hold the companies “responsible for their actions”.

“This is the worst man-made public health crisis in our state’s history. To put it bluntly, this crisis is devastating Oklahoma,” he said.

He said the company “embarked on a cynical, deceitful, multibillion-dollar brainwashing campaign to establish opioid analgesics as the magic drug.”

The case is the first of nearly 2000 cases pending against pharmaceutical companies across the US.

It comes after Oklahoma settled with Purdue Pharma (which produces the prescription painkiller OxyContin) for $US270 million ($A390 million) in March and Israeli company Teva for $US85 million ($A123 million) on Sunday.

Johnson & Johnson’s lawyers defended the company in court, saying there was government oversight over the drugs and cited warning labels on the products.

Lawyer Larry Ottway said Johnson & Johnson’s products made up a small share of opioids prescribed in Oklahoma.

“You have to examine the details because facts are stubborn things,” he said.

-with agencies