NEW YORK (CNN/Money) - Merck & Co. Inc. tried to patent a drug that would reduce heart attack risks for Vioxx users, three years before the company withdrew the painkiller because of safety concerns.

According to government records, the company applied for the patent in 2001. Merck voluntarily withdrew Vioxx, a $2.5 billion drug, on Sept. 30, 2004 after studying whether the medicine was linked to heart attacks and strokes, according to government records. However, the company says no such connection has been proven.

Shares of Merck (down $0.57 to $31.41, Research) fell more than 2.2 percent on the news, weighing on the Dow, which lost almost 1 percent by mid-afternoon.

In a statement released Thursday afternoon, Merck's lawyers said the patent application was to provide a medicine that would provide all of the cardiovascular benefits of aspirin without any of its gastrointestinal side effects, preserving the effectiveness of Vioxx.

A spokesman noted that the application did not indicate safety concerns by the company over Vioxx.

"This patent application has nothing to do with Merck's firm belief in the cardiovascular safety of Vioxx, both before the medicine was approved by the FDA and right up until Merck voluntarily withdrew Vioxx from the market," said a spokesman for Merck's law firm, Hughes Hubbard & Reed.

The spokesman also noted Merck did not pursue the patent application.

Plaintiffs' attorneys in a product liability case over Vioxx's side effects, however, contend that an internal Merck document proves that Merck executives sought the patent specifically to counter Vioxx's tendency to cause blood clots, the Philadelphia Inquirer reported Thursday.

The Food and Drug Administration declined to comment on the matter, noting it does not deal with patents.

In the 2001 application, the company looked to patent the aspirin-like drug to help prevent heart attacks in patients who could not take aspirin because of its gastrointestinal effects.

Merck wrote in its application: "For patients who are taking COX-2 selective inhibitors and who may benefit from the cardiovascular protective effect of aspirin, there remains a need for a cardiovascular protective treatment that does not expose them to increased risk for gastrointestinal side effects."

More than 2,000 Vioxx users have filed suit against the company, alleging that Merck knew about the cardiovascular risks, according to the Inquirer report. But Merck has denied the allegations, saying it recalled Vioxx as a precaution.

Based in Whitehouse Station, N.J., Merck is one of the largest drug makers in the world, with $22.9 billion in 2004 sales.

Want to catch up on all of the latest business news? Click here.