The U.S. House Energy and Commerce Committee is questioning Merck and Schering- Plough for details about the early release of study data related to the cholesterol drug Vytorin.

The committee said it wants details about why patient safety boards for trials involving Vytorin decided  to release their study data last year prior the conclusion of the studies, according to a letter sent to Merck and Schering-Plough by Energy and Commerce Committee Chairman Rep. Henry Waxman, D.- Calif. and Rep. Bart Stupak, D.-Mich.

Vytorin, sold under a Merck and Schering-Plough partnership, has been scrutinized for the last several years amid concerns about the drug's effectiveness with the release of the ENHANCE results at last year's ACC conference, and a potential link to cancer revealed in the SEAS trial.

In the letter, Waxman and Stupak said they wanted the names, affiliations and contact information for the patient safety boards for three trials involving Vytorin by March 6. The committee also wanted all documents relating to the SEAS trial published last year in the New England Journal of Medicine about Vytorin.

After a one-year review of the ENHANCE trial results, the FDA reported that while there was no significant difference in carotid artery thickness between patients taking Vytorin and those taking Zocor, it did manage to lower LDL levels. Therefore, the regulators encouraged patients to continue taking the drug, pending the results from IMPROVE-IT.

The drug is a combination of Zetia and Zocor. Vytorin, known as Inegy in Europe, and Zetia had combined sales of more than $5 billion in 2007, according to Dow Jones.