The "Enhance" trial studied a combination of Zetia and the statin drug Zocor – sold as Vytorin – in 720 patients with very high cholesterol, which is difficult to treat.
The study found the combination lowered cholesterol, but that it was no better than Zocor alone in reducing the growth of plaques in the carotid arteries of the neck. In fact, the numbers showed plaque build-up was slightly worse in the Zetia group, placing them at higher risk of heart attack or stroke.
Dr. Michael Blazing, a Duke University cardiologist and principal investigator in the study, called the difference in plaque build-up tiny – 0.005 millimeters using ultrasound measurements.
"The accuracy with which we can measure those numbers is limited, and the statistic said that those numbers were not different," Blazing said. "If you think of this in relative terms, that's one-tenth of the thickness of a sheet of average copy paper. That's the kind of measurement we're talking about."
Blazing also is the principal investigator in an ongoing trial looking at the the same medications with 12,000 patients. It's called the "ImproveIt" trial, with final results expected in 2010.
He said people taking Zetia don't need to change their medication based on the Enhance trial results.
Patients with an elevated LDL cholesterol – above 100 – should start with a statin, he said. Those who don't get to their LDL goal could consider adding an adjunctive agent like Zetia or niacin, he said.
"You have to be careful adding a number because you can add risk without adding benefit," Blazing said. "If you're a true believer in the number is what's important, then it's a clinical decision at this point. You can be done. If you're not a true believer and you're worried about the side-effects of a medication or kinds of medications, then you use a statin alone."