Thousands of personal injury lawsuits involving the painkiller Vioxx cannot be pooled together into a class action, a US federal judge has ruled.
Merck's liabilities linked to Vioxx could top $5bn
Judge Eldon Fallon refused a request to combine 7,000 lawsuits against drug firm Merck & Co, mainly because of the unique circumstances of each case.
A mass of lawsuits targeted Merck after a study found Vioxx may double the risk of heart attack or stroke.
The anti-inflammatory drug was withdrawn from the market in 2004.
In his 25-page ruling US District Judge Fallon said the " difficulties in class management overwhelm any efficiencies that could be secured through classwide adjudication".
"While the majority of plaintiffs in this case allegedly suffered either a heart attack or stroke as a result of ingesting Vioxx, the extent of each plaintiff's subsequent injuries varies widely," he added.
The decision means the lawsuits against Merck must be tackled on a case by case basis, news that has been welcomed by Merck's lawyers.
"We are pleased by today's order because it reaffirms our view that every case is different and should be tried individually," said Ted Mayer, a lawyer for Hughes, Hubbard & Reed, Merck's outside counsel.
So far, Merck has won seven of 11 cases that have been decided by a jury.
The judge's ruling came two days after Judge Fallon also rejected class action claims lodged by nine different countries, including the UK, Poland and Canada.
Judge Fallon said the plaintiffs should instead use their own legal systems to sue the company.
Merck still faces more than 7,000 outstanding lawsuits connected to Vioxx, which had previously been a best-seller, and experts believe its liabilities could top $5bn.
About 20 million people took Vioxx, including 400,000 in the UK, primarily to treat arthritis pain, after its launch in 1999.