ALBANY – The drug manufacturer Merck & Company is facing a flood of litigation after pulling its best-selling pain reliever, Vioxx, off the shelves late last month.

Merck officials say they issued the voluntary recall as soon as company research made it clear that patients who used Vioxx for 18 months or more faced a much higher risk of heart attacks and strokes than those taking placebos.

Attorneys who filed the first of what are expected to be thousands of personal-injury lawsuits charged that the pharmaceutical giant disregarded evidence of Vioxx-related problems dating back to 1999, the year the drug first went on the market.

Given that an estimated 20 million Americans have taken Vioxx over the past five years, and given that heart disease and stroke are common ailments, observers said this could become one of the biggest product-liability cases in history.

Scores of law firms are scrambling to take part, advertising heavily for clients in newspapers and on the Internet. Among them is Weitz & Luxenberg, a Manhattan firm that includes the speaker of the state Assembly, Sheldon Silver, as one of its affiliated attorneys.

“If you’ve been injured as a result of taking Vioxx for treatment of osteoarthritis, menstrual symptoms, or acute pain, your first call should be to your doctor,” the firm said in a recent newspaper ad. “Your second call should be to the law firm of Weitz & Luxenberg.”

In a recent statement on the fallout from its recall, Merck said it had been named in 300 lawsuits on behalf of 900 plaintiff groups in the first 15 days after announcing the recall. With its stock price down about 25% since the announcement, the company also expects to be sued by shareholders who lost money. Merck said it could not predict what it will cost to resolve these suits or whether its insurance would be sufficient to cover its liability and legal costs.

“A series of highly unfavorable outcomes could have a material adverse effect on the company’s financial position, liquidity, and results of operations,” the statement said.

The situation illustrates the high stakes world of the pharmaceutical industry, where a drug like Vioxx, which was generating $2.5 billion a year in revenue for Merck, can become a huge liability overnight.

The case also provides a Rorschach test for partisans in the debate over tort reform. Defenders of the civil liability system argue that Merck must be held responsible for aggressively marketing what turned out to be a dangerous medicine, and that trial lawyers will help by vigorously pursuing compensation for the injured parties.

“Fees are the last thing we’re thinking about at this point,” said one attorney suing Merck, Jeffrey Reiff of Reiff & Bily of Philadelphia.

Critics of the tort system contend that trial lawyers, with their widespread advertising, are likely to file thousands of frivolous cases along with the good ones, and the courts won’t necessarily do a good job of sorting them out.

“If someone is really injured be cause of an undisclosed and unknown defect in that product, it’s certainly fair for that person to seek compensation from the manufacturer,” said the executive director of the group Common Good, Franklin Stone. “The problem is the system isn’t fair about distinguishing between those who deserve compensation and those who don’t.

“Even when a company has done nothing wrong, the mere expense of having to go through litigation causes companies to want to reduce their risk and not enter a market,” Ms. Stone said.

A neurosurgeon and attorney from Long Island, Harvey Wachsman, said he believes both Merck and the U.S. Food & Drug Administration were negligent. When a previous study found that Vioxx patients suffered more heart problems than those taking naproxen, an over-the-counter pain reliever, the company argued that naproxen was preventing heart disease, he said.

“If you put something into the course of commerce, you’re responsible for what you’re doing,” Dr. Wachsman said. 1009 1857 1115 1868″They make billions and billions and there’s no protection for the public.”

The editor ofOverlawyered.com, Walter Olson, noted that lawsuits charging Vioxx-related health problems didn’t turn into a torrent until Merck issued a voluntary recall based on its own study – in effect, punishing the company for doing the right thing.

The recall “should not in itself indicate guilt,” Mr. Olson said. “However, it is felt by lawyers involved in drug litigation that a withdrawal will set the jury off thinking there is more of a problem. … You have a very troublesome incentive for manufacturers. If they do a recall or withdrawal they might be seen as liable.”

That heart disease and stroke are common diseases is a mixed blessing for both sides of this litigation, Mr. Olson said. On the one hand, it creates a huge pool of potential plaintiffs for lawsuits. On the other, it makes it harder to prove that the injury was a result of taking Vioxx and not a coincidence.

He said many law firms try to amass as many clients as possible, believing it gives them leverage in settlement negotiations with the manufacturer. Some might be positioning themselves for a claim to lead-plaintiff status if the lawsuits are consolidated into a class action.

When contacted by an employee of The New York Sun inquiring on behalf of a family member who had taken Vioxx, several law firms advertising on the Internet turned away the case when they learned the patient had not suffered signs of heart disease or stroke.

Not all the advertisers were so scrupulous. One Web page, at vioxx.x.yi.org, claimed that a Vioxx lawsuit could result in an “easy $1 million.” It encouraged would-be plaintiffs to find places still selling Vioxx and buy some, saying that would give them a case against the manufacturer and the pharmacy. For a fee of $100, the site offered “a document showing how an average person can benefit from this once-in-a-lifetime opportunity to become a millionaire.”

The operator of the page, who gave his name only as Leon, said he had done nothing wrong.

“I’m not encouraging people to lie,” he said. “Eventually the court will decide whether the case is valid or not.”