On Friday, a Texas jury ordered Merck to pay $253m (£141m) to the widow of a man who died in his sleep from a Vioxx-induced heart attack. British legal firms are predicting that claims from this country alone will run into the thousands.
Vioxx was taken off the market last September after a long-term study found it increased the risk of heart attacks and strokes.
The court rejected Merck's argument that he died of clogged arteries. But Merck intends to appeal against the decision and has promised to fight up to 4,200 lawsuits from across America. It also faces claims from India, China, Canada and Italy.
More than 500,000 Britons had taken Vioxx, one of a new generation of painkillers known as Cox-2 inhibitors. They were seen as a breakthrough in relief for arthritis sufferers because they did not have the side effects of established remedies.
A 52-year-old woman from Skelmersdale, Lancashire has already begun filing court papers in the state of New Jersey, claiming the drug caused two strokes. Christine Peckham (below) is one of 150 people contemplating legal action before this weekend's publicity.
Russell Spargo, of the law firm MSB, which is representing 60 British claimants, said yesterday: "We've been inundated with calls, all of them potentially strong cases. It is believed to have caused 28,000 deaths in America alone. I believe this could be the biggest legal action ever."
Gerard Dervan, a partner in the Liverpool law firm MSB, which is representing Ms Peckham, along with 60 other potential claimants, said: "The process is under way. We have a US attorney lined up and the files are in transit.
"It could be years before this case is heard in the UK, and then the costs could be astronomical and we will receive no public funding. The American system is more geared up for claims of this kind and there it is no-win, no-fee."
He said it might be the case that the drug was not properly scrutinised in the UK. "Certainly here in England the drug was approved in four weeks by British authorities and one would have to surmise that they did not do adequate research into the safety of this drug," he said. "One just wonders whether or not the mighty dollar was more advantageous than people's health."
He also said that if Merck loses more lawsuits it will be forced to negotiate a compensation package.
It is expected, however, that Merck will challenge the US court's ability to hear claims from outside America. One of Merck's arguments is that the nature of the drug meant it was taken by elderly people, for whom a stroke or heart attack is already a risk.
Vioxx is a source of particular controversy because of claims that key medical data about the drug and other Cox-2 inhibitors has been suppressed by the US regulator, the powerful Food and Drug Administration.
Last year The Lancet published trial results showing that unacceptable heart risks linked to the drug rofecoxib (sold as Vioxx) were evident four years before it was finally withdrawn by its maker.
An investigation by The Independent on Sunday earlier this year showed how the interests of commercial confidentiality meant that even suicides associated with trials of the new antidepressant Cymbalta had been kept from the FDA records. These include the widely reported suicide of 19-year-old Traci Johnson, a volunteer who hanged herself in one of manufacturer Eli Lilly's own testing suites during a trial of Cymbalta.
'I feel bitter and very, very angry'
Christine Peckham, now 52, was in pain from osteoarthritis when her doctor first prescribed Vioxx four years ago.
At first she was delighted. "The arthritis was very painful," she says. "I'd tried other drugs, but asked my doctor for something else, and Vioxx was the new wonder drug. It eased the pain considerably."
Less than two years later, however, Christine suffered a stroke. She didn't drink or smoke, she wasn't overweight and didn't have high blood pressure - all potential causes of strokes - and nobody could tell her why she had suffered a stroke at such a young age.
"I had the mother of all headaches," she says. "I went to bed and when I woke up my left side was numb and the left side of my face had dropped. The stroke was quite severe.
"A few months later I had another stroke. That has left me paralysed and with tunnel vision and epilepsy. I couldn't believe what was happening to me."
Throughout this period she had continued to take Vioxx until her GP told her to stop taking it, as there had been "a few problems".
"That's when I found out it caused strokes and heart attacks. It has ruined my life. I'm not being dramatic when I say that. I'm not dead but it took my life away. I can't do the things I used to: I can't go out, I can't read the paper. It has to be read to me. I was quite active. All that's gone. I feel bitter and very angry.
"Merck knew what was going on seven months before my stroke - they had memos from the Federal Drug Authority - but they carried on and put profit before people's lives. They should be held accountable.
"I'll be on benefits for the rest of my life, and my husband can't work as he has to look after me. The British taxpayer has to pay. Why shouldn't Merck pay from all the profits they've made?"