Mumbai: Clinical trials of Forest Laboratories Inc.'s Lexapro have proved it to be more effective than Eli Lilly and Co.'s Cymbalta in treating moderate to severe depression.

In an eight-week head-to-head study of the two medicines among 270 patients, Forest said Lexapro was the better tolerated of the two highly profitable drugs, the company said.

The study, funded by Forest, was intended to demonstrate that Lexapro was not inferior to Cymbalta, one of the researchers said.

"Going in we thought Lexapro would do as well and be better tolerated," Arif Kahn, medical director of the Northwestern Clinical Research Center in Bellevue, Washington and one of the study's lead investigators, said in an interview.

"This was not expected. I didn't think it would reach statistical significance," said Kahn, who prescribes both medicines for depression in his practice.

Against an expected 50 per cent improvement in patients' depression symptoms as measured by a standard depression rating system known as MADRS (Montgomery and Aasberg Depression Rating Scale), patients aged 18 to 80 showed a MADRS score of 26 per cent or greater.

Lexapro showed improvement level of 68 per cent compared to 52 per cent reached with Cymbalta. In addition, 44 per cent of the Lexapro patients experienced near total disappearance of depression symptoms compared with a 38-per cent improvement in the Cymbalta group.

Lexapro belongs to the selective serotonin reuptake inhibitor (SSRI) class of antidepressants and are among the most widely prescribed medicines for depression. Cymbalta belongs to a newer class called SNRIs that work on both serotonin and norepinephrine levels in the brain.

Lexapro, licensed by Denmark's H. Lundbeck, had third-quarter sales of $522.7 million. Cymbalta's third-quarter sales were $348.6 million, but the newer drug is growing at a much faster pace.