Although physicians like to think they practice evidence-based medicine, that appears to not be the case with prescribing the cardiovascular drug ezetimibe. And some critics say that use of surrogate markers to guide practice rather than clinical outcomes such as occurrence of myocardial infarction, stroke, or death has likely played a role.
Ezetimibe is an intestinal cholesterol absorption inhibitor found to reduce low-density lipoprotein cholesterol (LDL-C) levels by about 20% when given alone. It also further reduces LDL-C levels when added to statin therapy, which blocks cholesterol synthesis in the liver by inhibiting HMG-CoA reductase.
The Food and Drug Administration approved ezetimibe in 2002 for use in the United States primarily because it lowered LDL-C levels, a surrogate marker for prevention of cardiovascular disease. Whether ezetimibe improved clinically meaningful outcomes remained a question.
That question was somewhat answered in January 2008, with the announcement that the Ezetimibe and Simvastatin in Hypercholesterolemia Enhances Atherosclerosis Regression (ENHANCE) trial, sponsored and conducted by industry, found that the addition of ezetimibe failed to reduce atherosclerosis progression compared with simvastatin alone, despite lowering LDL-C levels. Atherosclerosis progression was determined by a change in the intima-media thickness of the walls of the carotid and femoral arteries—yet another surrogate end point (Kastelein JJP et al. N Engl J Med. 2008;358:1431-1443).
US and Canadian physicians continue to prescribe ezetimibe even after a study found giving the drug with a statin failed to reduce atherosclerosis progression compared with the statin alone.
The ENHANCE result prompted some leaders in the cardiology community to question ezetimibe’s place in cardiovascular disease treatment. Harlan Krumholz, MD, professor of medicine and epidemiology and public health at Yale University in New Haven, Connecticut, said the study should change practice. “Although not definitive, [ENHANCE] increases our uncertainty about the clinical value of this novel drug. Without some evidence of improved outcomes associated with its use, ezetimibe should be relegated to a last option for patients who need medication for hypercholesterolemia, and even in these cases, it is reasonable for clinicians and their patients to wait for further information before considering it,” he wrote in NEJM Journal Watch (http://tinyurl.com/pk9xr29).
So did the ENHANCE results change practice? In the United States, the answer is “somewhat,” while in Canada, the answer appears to be “no.”
In a study published in the American Heart Journal, researchers looked at ezetimibe prescription trends before and after ENHANCE, using data collected from CompuScript in Canada and IMS Health in the United States from January 1, 2002, to December 31, 2009. The researchers found the monthly number of ezetimibe prescriptions per 100 000 population rose from 6 to 1082 in the United States from November 2002 to January 2008 and then declined to 572 per 100 000 population by December 2009, a decrease of 47.1%. In Canada, however, use continuously increased from 2 to 495 per 100 000 from June 2003 (when the drug was approved in Canada) to December 2009 (Lu L et al. Am Heart J. doi:10.1016/j.ahj.2014.01.014 [published online February 27, 2014]).
Coauthor Cynthia A. Jackevicius, PharmD, MSc, a professor of pharmacy practice and administration at Western University of Health Sciences in Pomona, California, and an adjunct scientist, Institute for Clinical Evaluative Sciences, in Toronto, said her team was initially surprised by the Canadian results.
“Previous findings showed ezetimibe use in Canada experienced a more conservative uptake, so we expected to see a decrease in use in response to the ENHANCE study,” Jackevicius said. “So we looked for different factors, and one is the Canadian lipid guidelines, which specifically said ezetimibe could be added to statins, and that didn’t change after ENHANCE came out.”
A study of ezetimibe use in Saskatchewan, the only Canadian province that lists the drug for open formulary access, even though guidelines say it’s a second-line agent for lowering cholesterol, reflects Jackevicius’s team’s findings. Using data from provincial health administrative databases, the Saskatchewan researchers found that ezetimibe prescriptions were 2.5% of cholesterol-lowering dispensations in 2004 and 8.8% of such dispensations in 2011 (Alsabbagh WM et al. Can J Cardiol. 2014;30:237-243). The authors concluded that allowing unrestricted use of ezetimibe in Saskatchewan may have led to a large number of inappropriate prescriptions, at odds with Canadian clinical guidelines.
And although ezetimibe use declined in the United States, its use per 100 000 population is still greater than Canada’s, generating US expenditures of more than $2.2 billion in 2009.
Krumholz, one of the coauthors on the study with Jackevicius, remains perplexed as to the continuing popularity of ezetimibe. “The drug continues to defy gravity, and that’s probably a result of really strong marketing and the singular focus on cholesterol numbers,” he said.
Krumholz said heart health campaigns urging patients to “know your numbers” and treatment goals based on cholesterol measurements, such as getting asymptomatic individuals’ LDL-C levels below 130 mg/dL, have worked in ezetimibe’s favor at the expense of evidence-based medicine. “Is this the drug that lowers your LDL-C and helps you? We don’t know that,” he said. “The comfort of hitting a target offers little benefit if you don’t know that it is really protecting you.”
Although ENHANCE has not derailed ezetimibe prescribing, the newest cholesterol management guidelines just might. The guidelines, issued late last year by the American College of Cardiology and the American Heart Association, abandon the idea of reaching a target level for LDL-C, instead recommending the use of statins to reduce LDL-C levels only for certain types of patients.
Will this change in the guidelines affect ezetimibe prescribing? “It will be interesting to see what the guidelines will do,” Krumholz said.
Published Online: March 19, 2014. doi:10.1001/jama.2014.2896.
Mitka M. Ezetimibe Prescribing Fails to Keep Up With Evidence. JAMA. 2014;311(13):11279-1280. doi:10.1001/jama.2014.2896