Watson Pharmaceuticals Inc, the largest U.S. maker of generic birth-control pills, announced they have won U.S. health regulators´ marketing approval for their prostate enlargement treatment, once-a-day pill Rapaflo, generically silodosin.

The drug is designed to reduce symptoms of an enlarged prostate, including urinary pain and resistance.

Watson licensed the North American rights to Rapaflo from Japan´s Kissei Pharmaceutical Co in 2004. Kissei and Daiichi Sankyo have sold a twice-a-day version of the drug called Urief in Japan since May 2006.

An analyst at Natixis Belichroeder in New York told clients that Rapaflo could add $ 34.8 million dollars to Watson´s earnings by 2010.

Watson gets about 60 percent of its revenue from generics, and is seeking new products and cost reductions to remain competitive with U.S. rivals Barr Pharmaceuticals (being bought by Israel´s Teva Pharmaceuticals Industries Inc) and Mylan Inc.

Watson´s Rapaflo has several strong competitors in the prostate enlargement treatment market, such as Boehringer Ingelheim's Flomax/Alna ($ 764 million dollars in sales in 1H2008) and GlaxoSmithKline´s Avodant ($ 352 million dollars in the same period.)