NEW YORK (CNNMoney.com) - A new study shows that Vytorin, a cholesterol drug from Merck and Schering-Plough that combines Zocor and Zetia, significantly reduces cholesterol when compared to Zocor alone, the company said.

Vytorin reduced LDL, or "bad" cholesterol, by 52.5 percent, compared to 38.0 percent for Zocor, said Merck (unchanged at $34.76, Research). The results of the study were presented at an American College of Cardiology conference in Atlanta on Monday.

The study results might help Merck keep from losing patients to a cheaper, generic form of Zocor, when the blockbuster loses patent protection in June. Vytorin sales totaled $2.4 billion in 2005. Zocor sales totaled $4.4 billion in 2005.

The study also showed that Vytorin reduced C-reactive protein, considered a risk for heart disease, by 31.0 percent with Vytorin, compared to a reduction of 14.3 percent with Zocor, Merck said.

Vytorin is a combination of Zetia, a Schering-Plough (unchanged at $18.05, Research) drug that stops cholesterol absorption into the liver and intestine, and Zocor, which cuts cholesterol.

To read more about the impending patent loss to Zocor, click here.