New Delhi, Feb 08: Domestic drug major Dr Reddy's Laboratories (DRL) has said that the US Food and Drug Administration (USFDA) plans to review its application to market a version of Pfizer Inc's anti-hypertension drug Norvasc.

The FDA would stay the approval, granted on October 31, 2003, the Hyderabad-based pharma company said yesterday after receiving a letter from USFDA. Dr Reddy's version of Norvasc differs from Pfizer's in that it attaches the main chemical in the drug, Amlodipine, to a different salt. Pfizer had contended that it should have patent protection till January 2007. The FDA further indicated in the letter that it believes that the approval of Amvaztm, the brand name for Dr Reddy's product, did not rely on any proprietary data from Pfizer's NDA. The letter indicated the re-evaluation was prompted by questions raised about the source of the data relied on by FDA in its review, Dr Reddy's said. ''We are confident that FDA's initial decision was correct and remain optimistic of a positive outcome of FDA's re-evaluation,'' Dr Reddy's Laboratories CEO G V Prasad said. Norvasc is the world's top selling hypertension drug. Bureau Report