The new erectile dysfunction drug Cialis may improve erections in patients who undergo radical prostate cancer surgery, said the makers of the drug, Eli Lilly and Co. and Icos Corp. on Friday.

In A trial of the drug, which has been approved in Europe but is still awaiting approval in the United States, 62 percent of men who underwent a surgery known as bilateral nerve-sparing radical retropubic prostatectomy had improved erections.

By contrast, only 23 percent of men taking a placebo reported improved erections. The trial involved 303 men who took Cialis over a period of 12 weeks.

More than half of men who undergo this kind of radical prostatectomy experience some level of erectile dysfunction 18 months or more after the procedure, the companies said.

The data were released at the annual meeting of the Sexual Medicine Society in Denver.

Cialis is in a three-way battle for market share with Pfizer Inc.'s Viagra and GlaxoSmithKline Plc's Levitra.

GlaxoSmithKline released data at the same conference on Thursday showing that men who had failed treatment on Viagra had a good chance of succeeding on Levitra.

In a study of 463 men that lasted 12 weeks, men were three times more likely to complete sexual intercourse on Levitra than on a placebo. About 46 percent succeeded on Levitra compared with 10 percent on placebo.