A federal court judge ruled last week that drug-company Pfizer will maintain market exclusivity on Viagra until 2019.

Teva Pharmaceuticals, an Israeli drug company, had sued Pfizer earlier this year, claiming its patent on the erectile-dysfunction (ED) drug Viagra was invalid and unpatentable. Teva, which specializes in making generic versions of popular drugs, argued that it would have been easy for any researcher to discover that Viagra's active ingredient, sildenafil, would be effective in treating ED. As a result, Teva said, the discovery wasn't novel and therefore not worthy of patent protection.

U.S. District Court Judge Rebecca Smith sided with Pfizer in her decision on Friday, stated Teva had not shown “by clear and convincing evidence” that the patent was invalid.

A federal court judge ruled last week that drug-company Pfizer will maintain market exclusivity on Viagra until 2019.

Teva Pharmaceuticals, an Israeli drug company, had sued Pfizer earlier this year, claiming its patent on the erectile-dysfunction (ED) drug Viagra was invalid and unpatentable. Teva, which specializes in making generic versions of popular drugs, argued that it would have been easy for any researcher to discover that Viagra's active ingredient, sildenafil, would be effective in treating ED. As a result, Teva said, the discovery wasn't novel and therefore not worthy of patent protection.

U.S. District Court Judge Rebecca Smith sided with Pfizer in her decision on Friday, stated Teva had not shown “by clear and convincing evidence” that the patent was invalid.