Switching Statins Often Leads to Wrong Doses

Aug. 28, 2010— -- STOCKHOLM -- A third of patients on cholesterol-lowering therapy received inadequate doses of generic simvastatin after being switched from atorvastatin (Lipitor), an analysis of a large pharmacy database showed.

Because of differences in potency between brand-name statins and generic versions, doctors must adjust the number of pills patients take. What researchers found was that fewer than half of patients who switched from brand-name statins to generci received doses of equal potency after the switch. The switching occurred after a government-mandated change in rules for using branded statins in the Netherlands.

Statistical models suggested inadequate dosing would lead to a 5.6 percent increase in LDL (or bad) cholesterol, possibly increasing the risk of heart problems, according to a study that will be reported here at the European Society of Cardiology meeting next week.

"The predicted net effect of this would be at least a 5 percent to 6 percent increase in low-density lipoprotein cholesterol, which translates to a 3 percent average increase in the risk of heart disease and stroke," Dr. Danny Liew of the University of Melbourne in Australia said in a statement.

"Our study highlights the need for health policymakers to be conscious of the potential adverse and unintended consequences of policy changes and for clinicians to be aware of dose equivalences among statins," Liew added in an e-mail to MedPage Today.

The findings came from an analysis of a nationwide pharmacy database and included 39,031 patients switched from atorvastatin to simvastatin during the first quarter of 2009. The switches occurred after the Dutch government began requiring physicians to justify prescriptions for branded statins.

Liew and colleagues conducted the analysis after prescription data suggested that switching often resulted in simvastatin doses that did not have potency equivalent to that of atorvastatin. They determined relative potency on the basis of a published meta-analysis of randomized clinical trials comparing the two drugs.