Plaintiffs say the blood-thinning product made by Bristol-Myers Squibb has caused excessive bleeding, brain injuries, and even death.

Legal action is apparently moving forward involving lawsuits filed by thousands of people who say they suffered serious injuries by taking the once-heralded blood-thinning drug Plavix.

The California Supreme Court ruled late last month that eight product liability lawsuits against Plavix manufacturer Bristol-Myers Squibb and Plavix distributor McKesson Corporation can proceed in San Francisco Superior Court.

Those eight cases involved 678 plaintiffs. They may soon be joined by a multitude of other cases, involving about 5,000 plaintiffs, that have been filed around the country.

There is no word yet on whether Bristol-Myers Squibb or McKesson will appeal the California high court’s decision.

Officials at both companies did not respond to Healthline requests for an interview for this story.

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Plavix, also known by its scientific name clopidogrel, was first approved by the Food and Drug Administration (FDA) in 1997.

The drug is a blood thinner used to reduce the risk of blood clots. It is prescribed to people who have a higher risk of cardiovascular problems, such as heart attacks or strokes.

In the past, Bristol-Myers Squibb touted Plavix as being more effective than aspirin in preventing clots and reducing the risk of heart attacks.

The medication was a profitable one for more than a decade, reaching sales of $7 billion in the United States in 2011. At that juncture, it was the top selling drug in the country.

Sales dropped dramatically in 2012 after Plavix’s patent expired, and the FDA approved generic versions of the drug.

During its profitable history, Plavix has caused a host of health problems for thousands of people, said Hunter Shkolnik, an attorney whose law firm represents about 2,000 plaintiffs in this dispute.

He said some plaintiffs, especially older adults, suffered gastrointestinal bleeding.

Others suffered severe bleeding after receiving ordinary cuts and scrapes.

Some plaintiffs say they suffered brain injuries after bumping their heads and suffering unusually heavy internal bleeding.

In some of these cases, the patients died. In the California cases, 18 involve families of patients who died.

In addition, Shkolnik said, Plavix was ineffective in about 25 percent of the plaintiffs. In others, it was no more effective than aspirin.

“For the vast majority there was no reason to take this drug,” Shkolnik told Healthline.

The plaintiffs have listed more than a dozen accusations against Bristol-Myers and McKesson. Among the charges are negligence, false or misleading advertising, and wrongful death.

Shkolnik said Bristol-Myers Squibb was aware of some of the potential health risks associated with Plavix when the FDA approved the drug, but the drug manufacturer concealed this information.

He said the company then was “overly aggressive in marketing the drug” to consumers and physicians.

“They overstated the efficacy of the drug and understated its risks,” Shkolnik said.

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The current lawsuits are not the first time Plavix’s effectiveness and safety have been questioned.

In 2005, The New England Journal of Medicine published a study that concluded Plavix users had a higher rate of ulcers than people who took aspirin combined with a heartburn pill.

The following year, the journal published another study that stated Plavix combined with aspirin had no significant benefits over aspirin alone as a treatment for people at risk of atherosclerotic events.

In 2009, the FDA published an advisory saying Plavix may have reduced effectiveness in patients who don’t metabolize the drug well.

In 2010, the FDA issued a “black box” warning for Plavix on its reduced effectiveness for certain patients.

In 2014, state officials in Hawaii filed a lawsuit against Bristol-Myers Squibb and Sanofi, saying the companies failed to disclose that Plavix has little effect on 30 percent of the population there and increases the risk of gastrointestinal bleeding.

In June, a whistle-blower lawsuit was reinstated by a New Jersey federal judge. In the suit, a sales representative says she was instructed to promote Plavix as superior to aspirin in preventing blood clots in stroke patients.

In the California court case, Bristol-Myers officials said the case should not be adjudicated in California because their company is not based there. It’s incorporated in Delaware, headquartered in New York, and has substantial operations in New Jersey.

Company representatives added only 86 of the lawsuits’ 678 plaintiffs reside in California.

However, in a 4-to-3 decision, the justices noted that Bristol-Myers Squibb has five research facilities as well as sales offices in California.

They also said the company sold 187 million Plavix pills in California between 2006 and 2012. Sales of those pills were estimated at almost $918 million.

The court also noted that co-defendant McKesson is headquartered in San Francisco.

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