Cholesterol drug options won't include an updated combination drug from Merck & Co. after federal regulators rejected a proposed drug that included a generic version of Lipitor.

The Monday ruling put into question the approval of a drug that combines the top-selling pharmaceutical of all time, Lipitor, along with Zetia, another cholesterol drug developed by Merck.

The Food and Drug Administration Monday requested additional data on the compound, according to The Associated Press.

The proposed cholesterol drug would replace the existing combo pill from Merck, Vytorin, as the company's once robust cholesterol franchise sees losing sales.

Vytorin contains Zetia, an inhibitor of cholesterol absorption and a drug called Zocor, which falls into the statin-class of drugs that reduce the amount of cholesterol the liver naturally produces.

Generic versions of Pfizer's Lipitor flooded the market in November, which dampened Vytorin sales, the AP reported.

The new experimental drug is called MK-0653C and contains two distinct cholesterol-fighting medications.

In response to the additional data request from the FDA, Merck issued the following statement: Merck plans to discuss next steps with the agency in the near future, including new data that are expected to be available later this year, which may address the FDA's comments.

Merck officials also pointed media to three trials underway listed on ClinicalTrials.gov.

Merck & Co.