If you're one of the millions of people taking Zetia, a popular cholesterol drug, you may be worried about reports that it doesn't prevent heart attacks and strokes.

Zetia is a cholesterol-lowering drug, but not a statin like Lipitor and Zocor. Most people take Zetia in the form of Vytorin, which combines Zetia with Zocor.

But a small study recently released has some patients on these drugs worried. However, some cardiologists say there is nothing to worry about.

Doctors said they believe Vytorin is still safe and the study may be misleading:

In the study researchers examined the buildup of plaque in an area called insignificant, so-called surrogate markers, which don't actually measure cardiac risk.

"We didn't look at whether deaths from heart attacks were lessened," cardiologist Helene Glassberg, of the University of Pennsylvania, said.

Glassberg said another reason not to worry is that the study only looked at a specific population of patients -- those with heterozygous familial hypercholesterolemia.

"It's a rare genetic disorder. One in 500 have it, not the average person who comes in with high cholesterol and cardiac risk," Glassberg said.

"I think it's very important to emphasize that you should not stop taking your medication unless you speak with your physician," Glassberg said. "There was no increase of side effects, adverse effects, no negative outcome, it just didn't show the benefit we expected to see."

NBC 10 spoke with Merck/Schering-Plough Pharmaceutical, the makers of the drug.

Merck used to make Zocor, which is now generic called Simvastatin.

Schering-Plough discovered Zetia.

The two companies have a parent company that released a statement saying, "We were pleased to see that overall the safety profiles of Vytorin and Simvastatin (generic form of Zocor) alone were similar and generally consistent with their product labels. The overall incidence rates of treatment-related adverse events, serious adverse events or adverse events leading to discontinuation were generally similar between treatment groups."

Glassberg said if you do have the rare form of high cholesterol, you should not stop the medication either unless advised by a doctor. She said it's just too premature.

The drug maker is now conducting three more trials involving more than 20,000 patients to better evaluate the drug.