Shares of Merck (MRK) and Schering-Plough (SGP) were under pressure today. Bloomberg reports the companies’ joint venture drug Vytorin failed to prevent complications from heart disease.

Vytorin prescription have plunged about a third since January this year when a study called Enhance showed that the drug worked no better than just Zocor alone in reducing buildup in the brain’s main artery.

The most recent trial; however, confirms previous studies that the drug reduces the risk of coronary artery disease events, but not the rate of progression of aortic valve disease, according to the study’s chief investigator.

SGP dropped as much as -15% today while MRK fell -6.24%.

From the Bull Pen: SGP bulls can be comforted by biotech specialist Professor David Miller’s comments, that the good news is the study confirmed the drug’s primary use in reducing cardiac events related to fat in the arteries.

From the Bear Cave: Regardless of the Vytorin story, is the picture bright for MRK? Breaking the $35 support level would give bears more ammunition.