By Ransdell Pierson

NEW YORK (Reuters) - Merck & Co (MRK.N: Quote, Profile, Research) and Schering-Plough SGP.N delayed the release of their quarterly financial results so investors could first learn the outcome of a new study of their Vytorin cholesterol fighter, and both drug makers' shares fell on jitters about the impending trial data.

Schering-Plough dropped more than 7 percent, while Merck was down 3.5 percent. The companies pushed back their earnings releases to after Monday's stock-market close.

Merck and Schering-Plough sell Vytorin through a joint venture. It and a related drug called Zetia, with collective global annual sales of more than $4.5 billion, are Schering-Plough's biggest products and among the biggest for Merck.

Results of the Vytorin study, called SEAS, will be presented at a scientific meeting in London at 1 p.m. EDT. They will come on the heels of data from a failed earlier trial of Vytorin, released in January, that pummeled shares of both companies.

The latest study compares the blockbuster medicine to placebo among patients with aortic stenosis, irregular thickening of the main valve to the aorta that can lead to heart failure. An estimated 2 percent of people over age 65 have the condition.

Both companies had planned to report second-quarter earnings before the market opened on Monday.

The 1,873-patient SEAS study, meant to follow subjects for a minimum of four years, is the largest formal trial ever conducted in patients with aortic stenosis.

It is designed to determine whether aggressive cholesterol lowering can prevent heart attacks and cardiac-related deaths among patients who have the underlying condition although they do not have symptoms.