PHOENIX - Pharmacists stopped dispensing Vioxx and patients began asking their doctors about alternatives to the popular anti-pain drug after Merck & Co. pulled it from the market because new data found it doubled the risk of heart attacks and strokes.

"We immediately called the nursing units and pulled the medications," said Beverly Grove, assistant administrator at the Rest Haven-York nursing home in York, Pa.

Merck's stock plunged almost 27 percent — wiping out $28 billion of market value — on Thursday as the Whitehouse Station, N.J.-based pharmaceutical giant said the recall will hurt its earnings.

Vioxx is one of Merck's most important drugs, with $1.8 billion in U.S. sales in 2003 and global sales of $2.5 billion — 11 percent of the company's $22.49 billion in revenue that year.

Merck said approximately 2 million people worldwide use Vioxx, which is prescribed for arthritis, acute pain and disorders such as carpal tunnel syndrome. The company says it has been prescribed 84 million times.

"I'm going to check with my supplier and my doctor," Mike Adams of Sun City, Ariz., said after learning of the recall. Adams said he takes the drug occasionally for pain from his prostate surgery.

Dr. Kutaiba Tabbaa, director of pain management at University Medical Center in Tucson, Ariz., said switching to Pfizer Inc.'s Celebrex and its successor drug, Bextra, and other alternatives won't be a problem for most patients.

"There are no withdrawal symptoms and there are a lot of other medications available on the market," Tabbaa said.

Dr. Steven Abramson, director of rheumatology at New York University Hospital for Joint Diseases, said "there are very few patients for whom there won't be a good alternative drug."

Besides Celebrex, which Abramson said hasn't been linked to heart complications, alternatives include generic anti-inflammatory drugs such as ibuprofen, naproxen and aspirin.

Pharmacists at Holy Spirit Hospital in Camp Hill, Pa., began identifying Vioxx patients immediately after learning of the recall Thursday morning, said pharmacy director Gregory George.

Holy Spirit's medical staff had previously authorized a substitute for Vioxx, George said.

However, patients should take the initiative to contact their doctors. Many doctors don't have computer databases that let them quickly determine which of their patients are taking a specific drug, said Dr. Richard Pearis, a Phoenix orthopedic surgeon.

"We would hope that the patients would call us," said Pearis, who specializes in sports medicine and arthroscopy. "We'd tell them to stop taking it and what we'd like them to do."

Pearis said he would switch his patients to another anti-inflammatory drug.

Merck said the clinical trial data showed an increased risk of heart attack and other cardiovascular complications 18 months after patients started taking Vioxx.

The three-year study — aimed at showing that Vioxx could prevent the recurrence of polyps, which can turn cancerous, in the colon and rectum — was stopped after Merck discovered participants had double the risk of a heart attack compared to those taking a placebo. During the study, 10 patients died, five who had been taking Vioxx and five who took dummy pills.

At least one plaintiffs' attorney announced plans for a class-action lawsuit against Merck. Another claimed to represent 58 patients around the country allegedly harmed by Vioxx, including people who suffered a heart attack, stroke, internal bleeding or kidney failure.

Merck spokesman Tony Plohoros said the company anticipates additional personal injury lawsuits over Vioxx may be filed and will defend them vigorously.

Shares in Merck, one of the world's biggest drug makers, plunged nearly 27 percent Thursday on the New York Stock Exchange web sites. More than 140 million shares were traded, compared to a daily average below 10 million.

The Vioxx recall stands to benefit Pfizer, the world's biggest drug maker. Merck and Pfizer have been battling for market share, with Pfizer's Celebrex arthritis drug dominating the market with about $2.6 billion in U.S. sales alone last year.

Vioxx was labeled with a warning about heart risks in 2002 after Merck's own study in 2000 uncovered the increased risk of heart attack and other complications. The Food and Drug Administration (news - web sites) has been monitoring problems reported to it since then.

Tabbaa said he was among physicians who started steering patients away from Vioxx to alternatives because of earlier concerns about Vioxx.

"Two years ago I was using it like crazy," Tabbaa said.

Vioxx's removal will be a blow to hopes that it and other drugs in the class known as COX-2 inhibitors could be used to prevent cancer in people at high risk of developing it. A landmark study in 2002 showed that small, daily doses of aspirin could prevent colon cancer, and studies hinted that COX-2 inhibitors might do the same.

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Business Writer Linda A. Johnson in Trenton, Medical Writer Marilynn Marchione in Milwaukee and AP Writer Mark Scolforo in Harrisburg, Pa., contributed to this story.

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On the Net: http://www.merck.com