Trenton, N.J. ? Merck & Co. said Friday it will pay $4.85 billion to end thousands of state and federal lawsuits over its painkiller Vioxx in one of the largest drug settlements ever.

Company officials estimated the deal, if accepted, would end 45,000 to 50,000 personal injury lawsuits involving U.S. Vioxx users who suffered a heart attack or ischemic stroke, the type in which blood flow to the brain is blocked.

“Without this settlement, the litigation might very well stretch on for years,” Merck executive vice president Kenneth Frazier said during a conference call.

He called the agreement “responsible and reasonable” and allows Merck to better quantify its liability.

Negotiating teams met more than 50 times in eight states and spoke hundreds of times by telephone over many months to hammer out the deal, according to attorneys.

“I’m very happy with it,” said Chris Seeger, one of the six plaintiff lawyers who helped negotiate the settlement. “It’s a tremendous way to resolve this litigation.”

Merck pulled Vioxx from the market Sept. 30, 2004, after its researchers determined the blockbuster arthritis treatment, then pulling in about $2.5 billion a year, doubled the risk of heart attacks and strokes.

To qualify for a settlement, plaintiffs must have filed claims by Thursday and meet several criteria, including medical proof that they suffered a heart attack or stroke, that they received at least 30 Vioxx pills and that they received enough pills to support a presumption that they were ingested within two weeks before injury.