Lipitor beats Zocor, says Pfizer

NEW YORK (CNNMoney.com) -- Patients who switched from the cholesterol-cutting drug Lipitor to the competitor simvastatin increased their risk of suffering heart attacks and strokes, according to a study that Pfizer unveiled on Wednesday.

The study tracked thousands of patients in the U.K. from 1997 to 2005, said Pfizer Inc., (up $0.00 to $25.08, Charts, Fortune 500) the producer of Lipitor, the world's top-selling drug. All of these patients took Lipitor for six months, but then some of them switched to simvastatin, also known as Zocor, produced by Merck & Co., Inc. (up $0.00 to $50.04, Charts, Fortune 500) The study continued to track the 9,009 patients who stayed with Lipitor, and the 2,511 patients who switched to Zocor.

The Zocor patients experienced a 30 percent increase in the risk of major cardiovascular events, which includes heart attacks, strokes, certain types of heart surgeries, and death, according to Pfizer.

"It gives pause to the idea that switching is without consequence," said Dr. Michael Berelowitz, senior vice president of Pfizer's global medical division.

Pfizer, which conducted and paid for the study, presented its findings in Vienna at the European Society of Cardiology Congress 2007.

Merck was not immediately available for comment.

Pfizer said there was no difference in deaths between the two groups, but there was a 43 percent increase in all other cardiovascular events for the simvastatin group, including heart attacks, strokes and certain types of heart surgeries.

The study also found that the patients who switched from Lipitor to simvastatin were twice as likely to quit taking anti-cholesterol therapy. But Pfizer said the study did not track why some patients dropped treatment. Also, Pfizer said it didn't know why some patients switched treatment from Lipitor to the competing drug.

Merck's Zocor was one of the company's top blockbusters until its patent expired in June, 2006, precipitating a plunge in sales as generic drugmakers began to make low-cost versions of the drug.

Also, Zocor's patent expiration meant that Lipitor patients had the option of dropping their name-brand drug for the cheaper competitor, even though the two drugs are not the same, because they are based on separate molecular compounds.

Lipitor sales totaled $6.1 billion in the first six months of 2007, down 2 percent from the same period last year.