UPDATE 1-U.S. FDA warns Glenmark on unapproved drug

* FDA says company sold unapproved nitroglycerin

* Glenmark says evaluating situation

* Company says 2010-11 financial numbers not affected

WASHINGTON, March 16 (Reuters) - Glenmark Pharmaceuticals Ltd (GLEN.BO) sold nitroglycerin tablets without approval from U.S. regulators, the Food and Drug Administration said in a letter released on Tuesday.

"Based upon our information, there are no FDA-approved applications on file" for nitroglycerin tablets in doses of 0.3 milligrams, 0.4 milligrams and 0.6 milligrams, the FDA said in the letter.

Glenmark said in a statement that nitroglycerin was an old drug that was previously "grandfathered" in with a category of medicines sold in the United States prior to 1938 without approved applications.

The FDA has made an effort since 2006 to remove older unapproved drugs from the market.

Glenmark said it is "evaluating the situation and will take appropriate measures."

"We believe that the sales from nitroglycerin tablets will not have a significant bearing on our FY 2010-11 financial numbers," the company said.

The FDA posted the letter here#Recent. (Reporting by Lisa Richwine and Vidya Loganathan, editing by Gerald E. McCormick)