Cialis could top Viagra sales by 2006

Viagra is one of the best-selling drugs in the world and one of the most famous brand names ever.

But a report in a new pharmaceutical journal says that by early 2006, Cialis - the rival drug developed by Bothell-based ICOS Corp. - could overtake Pfizer Inc.'s Viagra as the most popular erectile dysfunction drug in the United States.

Fritz Krieger, editor of the Journal of Longitudinal Data, makes that prediction in an article for the publication's first issue this month.

"Cialis appears to be the main threat to Viagra," Krieger wrote in his article titled "E.D. Wars."

"Its 36-hour active life," he continued, "and the fact that it does not interact with high-fat foods or alcohol to the extent Viagra does, are both advantages bound to propel the drug to category leadership."

Matt Beebe, leader of the Cialis brand team at Eli Lilly & Co. that is jointly manufacturing and marketing the drug, wouldn't comment specifically on the journal report.

He said, however, that joint-venture partners Lilly and ICOS are pleased with the drug's U.S. sales over the past nine months.

"Some of the comments (Krieger) made are very consistent with the comments we're hearing back from doctors and patients," Beebe said. "The feedback we're receiving around the U.S. has been tremendously positive."

Pfizer representatives could not be reached for comment.

Krieger, formerly an executive in the pharmaceutical industry, is using new detailed data from prescription-tracking companies in his Ohio-based journal. This "longitudinal" data can show how long patients stay on a particular drug and details about patients' switching between brand-name drugs.

Using data gathered by Verispan, a prescription tracking service, Krieger found that Viagra has lost market share to Cialis and Levitra, made by Bayer and GlaxoSmithKline.