Cialis, the impotence drug that hit the U.S. market in late November, recently grabbed second place for new prescriptions, moving ahead of Levitra, which entered the market several months before it.

Neither drug has approached the still-dominant market share of Viagra, which lost its five-year monopoly in August 2003 when Levitra reached U.S. pharmacies. But the people who market Cialis haven't been shy, issuing a batch of announcements about prescriptions and patient preferences at home and abroad.

The question now for investors assessing the impotence drug market is whether Cialis' recent performance signals a trend -- or whether it's simply a case of premature self-congratulation.

Wall Street analysts are impressed with Cialis' gains, but they'd also like to see several more months of data. Additional time and information would lessen the initial impact of free samples, vouchers and other distractions from pure revenue recognition that have characterized the launches of Cialis and Levitra as well as the defense of Viagra.

Doctors welcome the competition because they believe more drugs will encourage more men to seek help for impotence. But doctors are as mystified as analysts on what product will eventually sell best.

"The companies have flooded the market with free samples," said Dr. Wayne Hellstrom, professor of urology at the Tulane University School of Medicine in New Orleans, who has participated in clinical trials for all three impotence drugs. "There's so much out there. It will be hard to get a feeling for what patients want for six to eight months."

Competition Intensifies

Cialis was developed by the small biotechnology company Icos ( ICOS), which has entered into a joint venture for marketing and co-development with Eli Lilly ( LLY).

Levitra was developed by Germany's Bayer ( BAY), which has joined forces to market the drug with GlaxoSmithKline ( GSK).

And Viagra, which reached the U.S. market in 1998, is made and marketed by Pfizer ( PFE).

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