May 14 (Bloomberg) -- AstraZeneca Plc, the U.K.'s second-largest drugmaker, won U.S. approval to widen the use of its Seroquel antipsychotic medicine to treat bipolar disorder, pitting the treatment against Eli Lilly & Co.'s top-selling Zyprexa and Bristol-Myers Squibb Co.'s Abilify.

Patients may take the therapy as an adjunct to the standard treatments lithium or divalproex, London-based AstraZeneca said today in a statement.

Seroquel brought in $4.03 billion last year, making it AstraZeneca's second-best-selling product after Nexium for ulcers. AstraZeneca is trying to broaden the medicine's use to protect sales under threat from generic copies. The drugmaker this month asked the Food and Drug Administration to approve the therapy to treat generalized anxiety disorder.

``Seroquel is increasingly being rolled out for additional indications and may, in due course, become the go-to product for depressive disorders,'' Charles Stanley analyst Jeremy Batstone-Carr said in an e-mail.

AstraZeneca gained 39 pence, or 1.9 percent, to 2,130 pence in London trading. The stock has lost 1.6 percent this year.

Bipolar disorder was once known as manic depression. In classic, adult versions of the disease, people stay lodged for weeks or months in states of deep depression, then shift to a manic phase in which they sleep little, have intense energy, talk rapidly, and may engage in risky behavior.

Patent Suits

The U.K. drugmaker has patent infringement cases pending against Teva Pharmaceutical Industries Ltd. and Novartis AG's Sandoz Inc. to defend Seroquel against cheaper generic copies. Teva and Sandoz have applied for approval to market versions of Seroquel in the U.S. before a key patent expires in 2011.

If approved for the anxiety indication, Seroquel would compete with GlaxoSmithKline Plc's Paxil and Eli Lilly & Co's Cymbalta.

To contact the reporter on this story: Trista Kelley in London at tkelley2@bloomberg.netAngela Cullen in Frankfurt at acullen8@bloomberg.net

Last Updated: May 14, 2008 12:07 EDT