The generic threat to Eli Lilly's Cymbalta has loomed into view with news that the US Food and Drug Administration has given a tentative nod to copycat versions of the blockbuster antidepressant.

India's Sun Pharmaceutical Industries and Impax Laboratories of the USA have both revealed that the regulator has tentatively approved their Abbreviated New Drug Applications for generic versions of Cymbalta (delayed-release duloxetine). The drug, a serotonin-norepinephrine reuptake inhibitor, is not due to go-off patent in the USA until 2013.

However, the competition is lining up and once protection goes, Lilly will suffer as Cymbalta is a massive earner. In the USA alone, annual sales are around $3.00 billion, although they dipped 1% in the last quarter there to $643.2 million.

The FDA approved Cymbalta for major depressive disorder in 2004 and diabetic peripheral neuropathy in that same year. This was followed by green lights for generalised anxiety disorder and maintenance treatment of major depression in 2007 and fibromyalgia in 2008, while earlier this month it secured another approval from the agency, for the management of chronic musculoskeletal pain.