NEW YORK -- The makers of cholesterol drugs are promoting their products ahead of a major change that is expected to trigger more competition in the market for such drugs.

The makers of Vytorin announced at a medical meeting on Sunday that their product lowers cholesterol better than Crestor. Meanwhile, Crestor's manufacturer said that when taken in combination with another drug, its product achieves unprecedented cholesterol reduction.

Later this month, Merck & Co's Zocor will lose patent protection, and health plans are aggressively try to promote low-cost generic versions of the drug for patients who don't require a major cut in their cholesterol levels. Experts said Pfizer Inc.'s Lipitor will suffer most in the new environment because many patients on low doses of its medicine could reach the necessary cholesterol level at a high dose of Zocor.

However, that means Lipitor, Crestor and Vytorin will be battling more fiercely for the patients who need to slash their cholesterol.

In a six-week trial of 2,855 patients, those taking Vytorin reduced their cholesterol anywhere from 52 percent to 61 percent, depending on which of the three doses studied they were taking. Three strengths of Crestor were studied, reducing cholesterol between 46 percent and 57 percent, depending on the dose.

Vytorin is made by a joint venture between Merck and Schering-Plough Corp. and is a combination of two drugs: Zocor a statin which inhibits the production of cholesterol in the liver; and Zetia, which blocks absorption of cholesterol in the intestine. Crestor, a statin, is made by AstraZeneca PLC.

Medical guidelines recommend that very high risk patients such as those who have coronary heart disease should push their LDL or bad cholesterol level to 70 or below while high risk patients reduce it to 100 or less.

In a sub group of 715 high risk patients, Vytorin lowered cholesterol levels to below 70 percent and in 50 percent of patients compared with 29 percent of patients taking Crestor. Ninety percent of the high risk patients on Vytorin lowered their cholesterol to less than 100 compared to 82 percent of the Crestor patients.

A different study found that after six weeks, patients taking the highest dose of Crestor combined with Zetia, reduced their cholesterol by 70 percent, which AstraZeneca claims is a first. Patients in the other arm of the study, who were taking Crestor alone, saw their cholesterol fall an average of 57 percent. There were 469 patients in the study and they participated in a dietary program for six weeks before beginning drug treatment.

In the study, 94 percent of patients reduced their bad cholesterol level to below 100 , compared to 79 percent of patients taking Crestor alone.

The results from both studies were revealed at the International Symposium on Atherosclerosis.

Merck shares rose 5 cents to close at $34.46 on the New York Stock Exchange, while Schering-Plough shares dipped 20 cents to $19.05. Shares of London-based AstraZeneca, which trade on the NYSE, rose 32 cents to $56.62

On the Net:

Merck: http://www.merck.com

Schering-Plough: http://www.scheringplough.com

AstraZeneca: http://www.astrazeneca.com