There's no evidence Merck & Co.'s blockbuster cholesterol drug Vytorin causes cancer, federal regulators said Tuesday. They reviewed reams of data after a patient study last year raised suspicions of a link, weakening sales already hurt by questions about the drug's efficacy.

The Food and Drug Administration said Tuesday it reviewed data from that study and two others and found no evidence linking Vytorin to a higher risk of cancer or death from cancer. Still, the agency said it cannot definitively rule that out.

"We're pleased with the conclusions reached by the FDA," said Merck spokesman Ron Rogers.

Vytorin, a top moneymaker for Merck, combines two types of brand-name cholesterol pills, Zetia and Zocor, which is available as an inexpensive generic drug. At their peak, Vytorin and Zetia generated more than $5 billion a year in sales combined.

But starting in January 2008, research indicated that Vytorin was no more effective at limiting plaque buildup in arteries than Zocor, which costs about one-third as much. That June, preliminary results from a study known by the acronym SEAS indicated a possible increased risk of cancer in patients getting Vytorin, compared to those getting dummy pills.

In August 2008, the FDA said it would do an extensive review of the data. Its results, reported Tuesday, are based on several studies of Zetia and Vytorin, including animal testing and patient studies from the SEAS trial to two large ongoing studies of the drugs' effects on the cardiovascular system.

The FDA said that while there is lots of evidence Zocor is not linked to cancer, long-term patient data on Zetia, the other component of Vytorin, "is insufficient to definitively rule out a cancer risk at this time."

"FDA is not advising healthcare professionals or consumers to stop using these medications, but to continue to evaluate the clinical benefits and potential risks of Vytorin or Zetia compared to other FDA-approved cholesterol-lowering medications," the agency said in a statement.

It advised consumers with questions to consult their doctor.

"Merck strongly supports the efficacy and safety profiles of Vytorin and Zetia," Rogers said.

Merck, based in Whitehouse Station, N.J., became the world's second-biggest drugmaker in October with its $41.1 billion acquisition of Schering-Plough Corp., its longtime partner in marketing Zetia and Zocor.