DOW JONES NEWSWIRES

U.S. prescription volume for cholesterol drugs co-marketed by Merck & Co. (NYSE:MRK) ( MRK) and Schering-Plough Corp. (NYSE:SGP) (SGP) continued to decline - but at a far smaller rate - in May, according to IMS Health Inc. (NYSE:RX) (RX).

Figures from the prescription-data vendor posted on Schering-Plough's (NYSE:SGP) Web site showed total combined U.S. prescriptions for Vytorin and Zetia fell 1.1% to 2.5 million last month from the April total.

They dropped 11% from March to April and have declined 23% since January, when data from the Enhance trial showed that Vytorin - a combination of Zetia and the drug simvastatin - was no better than simvastatin alone at slowing thickening of the arteries despite producing a greater decline in bad cholesterol. Simvastatin is available as a generic and was a blockbuster for Merck (NYSE:MRK) under the brand Zocor before its patent protection expired in 2006.

The initial disclosure of the Enhance results immediately caused doctors to write fewer prescriptions for Vytorin and Zetia, with February's volume dropping more than 13% from January levels. But trends stabilized in March, with prescriptions inching up slightly as Merck (NYSE:MRK) and Schering-Plough (NYSE:SGP) defended the effectiveness of their drugs in a marketing push to doctors.

That March plateau, however, gave way at the end of the month, when researchers presented the full results of the Enhance study at a prominent meeting of cardiologists. A panel of doctors at the meeting recommended more limited use of the drugs, setting the stage for April's decline.

Last month, Schering-Plough (NYSE:SGP) disclosed that the U.S. Department of Justice has asked for information and documents related to its handling of the Enhance study. Members of Congress have asked Schering-Plough (NYSE:SGP) for witness interviews, documents and information on various issues related to the Enhance trial.

First-quarter sales of the drugs rose about 6% to $1.2 billion, a considerable slowdown from 2007 when growth was more than 30%. Both Merck (NYSE:MRK) and Schering-Plough (NYSE:SGP) have announced job cuts, partly in response to the downturn in sales for their cholesterol drugs.

Total U.S. prescriptions for cholesterol-managing drugs rose 1.3% to 19.8 million in May. They are down 2.9% from January.

Merck's (NYSE:MRK) shares closed up 1.3% to $35.13 on Friday and gained 2 cents in after- hours trading. Schering-Plough's (NYSE:SGP) were flat after hours at $18.57, after closing up 3.5%.

-By Kathy Shwiff, Dow Jones Newswires; 201-938-5975; Kathy.Shwiff@dowjones.com

    (END) Dow Jones Newswires   06-20-08 1901   Copyright (c) 2008 Dow Jones & Company, Inc.