Pfizer Inc said that a federal court jury in the Eastern District of Virginia (Alexandria) has ruled unanimously that Pfizer does not infringe Synthon IP's US patent covering a process for making amlodipine, the active ingredient in Norvasc.

Norvasc is the world's most-prescribed branded medicine for treating hypertension. The jury also found that the patent is invalid on multiple grounds, a Pfizer release stated.

"Today's unanimous decisions underscore our determination to defend our products against unwarranted attacks and to support research-based medical innovations that benefit millions of patients," said Allen Waxman, Pfizer's general counsel.

Synthon IP, a US subsidiary of Dutch company Synthon BV, brought its suit against Pfizer in November 2005, asserting that Pfizer infringed a Synthon patent issued in 2003. This patent, Synthon claimed, covered Pfizer's process for making amlodipine -- a process Pfizer had not only published but has been using for over 15 years.