NEW YORK (CNNMoney.com) - Merck is denying news reports that suggest new data from the drug maker indicates Vioxx increased heart attack risks earlier than previously reported and that the risk for stroke persisted long after the patient stopped taking the drug.

Merck pulled Vioxx, an arthritis painkiller, off the market in 2004 after its "Approve" study showed an increased risk of blood clot-related heart attacks and strokes in patients who took the drug for at least 18 months. But The Wall Street Journal reported Thursday that an internal document from Merck showed that heart attack risks actually increase in the first four months of use.

The newspaper said it gleaned this information from Merck's 107-page Vioxx summary. But Merck said the conclusion reached by the newspaper was "not scientifically appropriate."

"The new Approve data do not establish that the risk for Vioxx starts earlier than had previously been reported," said Merck in a press release.

Reuters reported late Thursday that experts who reviewed the new data presented to U.S. health regulators were also concerned that patients were at risk of suffering a stroke even after they have stopped taking Vioxx.

The new data showed seven Vioxx users had strokes and two had mini-strokes in a year-long follow-up period after they had stopped taking the drug compared with no strokes in the placebo group, the news service reported.

"These data raise some very important questions because for a while we assumed Vioxx caused temporary problems, and here it is more than that. It could be causing permanent damage," Dr. Curt Furberg, a member of the FDA Drug Safety and Risk Management Advisory Committee, said in an interview with Reuters after reviewing the data.

Any piece of new information regarding Vioxx is likely to be used as ammunition, by lawyers from either side, in upcoming lawsuits. Since the withdrawal of Vioxx, formerly a $2.5 billion-a-year drug, about 11,500 lawsuits have been filed against Merck by former Vioxx patients or families, blaming the drug for fatal and non-fatal heart attacks. Merck's (up $0.79 to $35.13, Research) stock price has plunged 24 percent since Sept. 29, 2004, the day before the withdrawal.

One attorney who is involved in 950 Vioxx product liability cases told Reuters that the new data could bring Merck closer to settlement talks, which would include short-term users.

"Every little study like this helps," attorney Kenneth Moll told the news service. "It's significant if Merck is looking at a global settlement because they can't exclude under 18 months users."

Merck has consistently said that its drug hasn't killed anyone and has denied allegations that it deliberately misled doctors and patients about the drug's risks. Merck has vowed to fight all cases, one at a time if necessary. So far, Merck has won two cases, lost two, and there was a split verdict in another.

The next case is scheduled for June 6 in New Jersey Superior Court in Atlantic City, where thousands of the cases have been filed in the company's home state. Merck, America's no. 2 drug maker with $22 billion in 2005 sales, is based in Whitehouse Station, N.J.

--from staff and wire reports

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To read about the most recent Vioxx verdict, click here.

To read about Merck's dance with the religious right, click here.