The makers of popular cholesterol drugs Vytorin and Zetia are being sued in states across the country over allegations that Merck & Co. and Schering-Plough Corp. misled consumers into thinking the drugs were more effective than generic ones.

Lawsuits have been filed in federal courts in states including California, Florida, Louisiana, Minnesota, Mississippi, New Jersey, New York and Ohio, according to court documents and interviews with attorneys. The consumer fraud suits, which all seek class-action status, were filed on behalf of patients and medical insurers who paid for the expensive cholesterol drugs.

The lawsuits come less than two weeks after Merck and Schering-Plough released a controversial study that raised questions about whether Vytorin and Zetia are more effective than generic drugs. The companies have a joint venture that markets Vytorin, which combines Merck’s Zocor and Schering-Plough’s Zetia.

Additional suits are pending in several other states and Puerto Rico and may eventually be filed in every state but Michigan, which bars such lawsuits against drug makers, said Louisiana attorney Daniel Becnel, who is coordinating filings with firms in other states.

“We just have hundreds and hundreds of (potential) clients contacting us every day,” asking to be represented in the matter, he said Thursday.

Becnel said he has already filed a motion for the suits to be consolidated in a single location under one federal judge.

In the Florida lawsuit, Marion J. Greene, 72, of Niceville, alleges the drug makers violated consumer protection laws in all 50 states through the marketing and sale of Vytorin and Zetia.

“I feel I’ve been intentionally misled by companies whose main pursuit is profits, rather than health,” Greene, who took Vytorin for nearly two years, said in a statement.

The Florida lawsuit seeks to recoup the difference in cost between generic cholesterol drugs that cost about one-third as much Vytorin or Zetia, as do suits in other states.

“The cost of those drugs is two-thirds more than the generic, which has the same benefit,” said one of Greene’s lawyers, Tim Howard of Tallahassee, Fla. Given that the two drugs have combined annual sales of about $5 billion, he estimated up to $3.5 billion might be recovered by all the suits.

Merck spokeswoman Amy Rose said the company couldn’t comment on the lawsuits because it had not seen them.

“Vytorin and Zetia have been shown to reduce LDL cholesterol in numerous clinical studies and they have been approved by the FDA for that indication,” she said Thursday. “The company will vigorously defend against any allegations or claims to the contrary.”

Schering-Plough spokeswoman Rosemarie Yancosek also said her company will vigorously defend itself.

The companies’ study essentially found that Vytorin was no better at reducing plaque buildup than Zocor, which is available as an inexpensive generic drug called simvastatin. Vytorin did reduce cholesterol levels a little more than Zocor alone.

The companies did not release results of the study, which was completed in April 2006, until Jan. 15 — five weeks after the U.S. House Committee on Energy and Commerce wrote to the chief executives of Merck and Schering-Plough inquiring about the delay and demanding documents and interviews with company officials.

The day after the results were released, the American Heart Association and American College of Cardiology essentially defended the companies, saying patients should not panic or stop taking Vytorin or Zetia without consulting their doctor, and that further research is needed to determine the best cholesterol-cutting strategy.

The House committee, which also is probing the two drug makers’ handling of advertising for the products, on Thursday wrote to their CEOs, demanding records of their financial support of and recent communications with the two heart specialty groups.

“We are concerned that both Merck and Schering-Plough have financial ties to the AHA and ACC such that their advisories related to cholesterol medications may be compromised,” the letter said. “We are also curious as to whether Merck and/or Schering-Plough may have had direct input into the AHA and ACC statements.”

Amid the controversy, Merck and Schering-Plough have temporarily halted TV ads for both Vytorin and Zetia.

Also Thursday, prescription-tracking firm ImpactRx reported that in the past week primary care doctors have sharply cut back the number of new prescriptions for Vytorin they are writing, from 15 percent of new cholesterol drug prescriptions to just 5 percent.

In trading Thursday, Merck shares fell 75 cents, or 1.5 percent, to $49.56, while Schering-Plough shares rose 58 cents, or 3 percent, to $20.17.