Sept. 5, 2007 -- Patients who switch from the statin drug Lipitor to a generic version of another statin may be more likely to suffer strokes, heart attacks, and death, a new study from Lipitor manufacturer Pfizer shows.
Researchers for the drug maker reported a 30% increase in risk for major cardiac events or deaths from all causes among patients who switched from Lipitor to simvastatin, the generic version of Merck & Co's cholesterol-lowering drug Zocor.
The generic statin was approved for sale in the U.S. in June 2006. It has been available in the U.K. since 2003.
Pfizer researchers compared outcomes among patients taking Lipitor who were and were not switched to simvastatin.
They say the findings highlight the potential for increased risk when patients are switched from one statin to another.
But all agree that they don't prove Lipitor is better or safer than a different cheaper, generic statin.
"We can't say from this study that switching is bad or that one statin is better than another. You would need a randomized, clinical trial to say that," cardiologist Berkeley Phillips, MD, of Pfizer tells WebMD.
"But there has been a lot of switching in the U.K. and across Europe, and this does raise concerns about policies that advocate widespread switching for purely economic reasons with little thought to a patient's individual risk," he says.
Using anonymous patient records from a medical database in the U.K., Phillips and colleagues compared cardiac outcomes and deaths from all causes among 2,511 patients who took Lipitor for at least six months and were then switched to generic simvastatin with just over 9,000 patients who remained on Lipitor.
The patients in the two treatment groups were matched for age and certain cardiovascular risk factors. But it was not known why patients switched medications or how many deaths were due to cardiovascular causes.
Compared with the patients who remained on Lipitor, those who switched to simvastatin were 43% more likely to suffer from a major cardiovascular event such as heart attack or stroke. They were twice as likely to suffer strokes, and 36% more likely to have heart attacks, although the data for heart attack risk was not statistically significant.
Patients who switched were also twice as likely to stop taking their medication against doctors' orders.
The findings were presented in a poster session in Zurich Wednesday during the final day of the annual European Society of Cardiology Congress.
More Questions Than Answers
Cardiologist Robert Bonow, MD, tells WebMD that the study raises more questions than it answers.
Bonow is chief of cardiology at Chicago's Northwestern Memorial Hospital and a past-president of the American Heart Association.
He points out that the differences among the two treatment groups could help explain the different outcomes.
"Switching just because a drug is cheaper is not the right thing to do," he says. "Many patients will do fine on the generic drug, but patients have to be followed carefully to make sure they achieve the [cholesterol] control you are aiming for. You can't just switch them and say, 'See you next year.'"
A spokesman for simvastatin and Zocor manufacturer Merck & Co. declined comment on the study Wednesday, saying company officials had not had a chance to review the data.
"The safety and efficacy of Zocor has been well documented for more than 15 years," Ian McConnell told WebMD.