Global pharmaceutical major Pfizer has taken legal against Dr Reddy's Laboratories (DRL) over its anti-cholesterol medicine Lipitor, which is the world's largest selling drug having sales worth more than $8 billion.

Pfizer asked a judge to forbid sales of generic variants of 'Lipitor' until 2017.

Hyderabad-based Dr Reddy's has formulated Lipitor's generic variant, and has sought the USFDA's nod to sell copies of Lipitor in the market.

In a declaration, Dr. Reddy's stated, "Given that this action stays approval of our ANDA until the case is resolved, it is not surprising that Pfizer has sued us. We are, however, confident of our position and are working to resolve the matter as quickly as possible."

Previously, DRL and its US arm notified Pfizer in October 2009 regarding the filing of an application with the USFDA looking for authorization to sell Lipitor's generic version.

According to the US regulations for generic drugs, when a patent is defied, the maker is informed about it.

New York-based Pfizer, with $48.2 billion in total sales during the last year, made $12.4 billion in 2008 Lipitor sales, $7.7 billion of which were from the US market.

A Dr Reddy's spokesperson said, "We are confident of our position and are working to resolve the matter as quickly as possible."