Eli Lilly and partner Boehringer Ingelheim have been boosted by the news that the US Food and Drug Administration has given the green light to a new use of the firms’ antidepressant Cymbalta.

The agency has approved Cymbalta (duloxetine) for the treatment of generalised anxiety disorder based on the results of three randomised, double-blind, placebo-controlled studies in which the safety and efficacy of duloxetine in the treatment of GAD was studied in more than 800 non-depressed adults. In all of the studies, Cymbalta significantly improved anxiety symptoms (46%) compared with patients who received a placebo (32%).

The companies noted that Cymbalta was approved in Mexico for the treatment of GAD in October 2006 and they are evaluating further submissions in other regions, including Europe. They estimate that over seven million Europeans may have the disorder which is “more than simple anxiety.” Because it presents with a variety of symptoms, both anxious and physical, “it can be difficult to diagnose.”

Duloxetine was previously approved for the treatment of depression and diabetic peripheral neuropathic pain in many countries and is approved in some places for stress urinary incontinence, however this latest approval for GAD can only boost the already-impressive sales of Cymbalta. Lilly’s fourth-quarter sales of the drug soared 85% to $424.1 million on the back of a massive sales and marketing campaign, and full-year turnover hit $1.32 billion, giving the drug blockbuster status in only its second full year on the market.

Cymbalta is now expected to make inroads into the market share of Wyeth’s blockbuster Effexor (venlafaxine) which is also approved for GAD. However many other compounds have fallen by the wayside in this area, notably Cephalon’s epilepsy drug Gabitril (tiagabine), while Novartis recently terminated its investigational GAD drug XBD173.