The share price of US drug company Merck has fallen to an eight-year low after it was forced to withdraw a painkiller due to side effect fears.
Merck's stock plunged 26.8% on Thursday after it removed the Vioxx product from all markets due to an increased risk of heart attack and stroke.
The announcement was immediately followed by a US lawsuit claiming the firm misled users, and more may follow.
Used to treat arthritis pain, Merck sold £2.5bn worth of Vioxx in 2003.
Vioxx has been on the market since 1999 and is used by 2 million people worldwide and by 400,000 in the UK.
"While we recognize that Vioxx benefited many patients, we believe this action (the withdrawal) is appropriate," said Peter Kim, president of Merck Research Laboratories.
The first lawsuit against Vioxx and Merck has been filled in Oklahoma on behalf of a local resident. It could however turn into a broader class action case.
William Federman, a lawyer at Federman & Sherwood, one of the legal firms that has filed the suit, said Merck had failed to warn that the drug was defective.
Yet other analysts said Merck has acted as promptly as possible.
Merck's chief executive Raymond Gilmartin confirmed to the BBC World Service that the company was withdrawing Vioxx with immediate effect.
"We are taking this action because it best serves the interests of the patient," he said.
"A voluntary withdrawal is the responsible course to take," he added.