TRENTON, N.J. — There's no evidence Merck & Co.'s blockbuster cholesterol drug Vytorin causes cancer, federal regulators said yesterday. 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 yesterday 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 combined sales.

But research released in January 2008 indicated Vytorin was no more effective at limiting plaque buildup in arteries than Zocor, which costs about one-third as much. Public release of the unfavorable data had been held up for so long that a congressional committee investigated.

In July 2008, preliminary results from a study known by the acronym SEAS indicated a possible increased risk of cancer in patients getting Vytorin.

The SEAS study aimed to determine whether Vytorin could reduce clogging of the aorta, making it an alternative to surgery. The 1,873-patient study showed no such benefit and, surprisingly, found about 50 percent more new cancer cases and cancer deaths in patients who received Vytorin, compared with those who took dummy pills.

The cancer result was suspicious, given that patients were only followed for four years on average and cancer normally develops slowly. But news of the finding hammered the stocks of both Merck and Schering-Plough Corp., its partner in marketing Vytorin and Zetia. Combined sales of the drugs kept falling but appear to have leveled off at an annual rate of about $4 billion.

In August 2008, the FDA began an extensive review of the data. Its results, reported yesterday, 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. Those studies, known by the acronyms SHARP and IMPROVE-IT, are expected to wrap up in 2010 and 2012, respectively.

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."

It advised consumers with questions to consult their doctor.