AstraZeneca has lost a key patent case in the United States over its heart drug Toprol XL. The decision of Judge Rodney Sippel of the US District Court for the Eastern District of Missouri stated that the compound patent (US Patent Number 5,081,154) and the composition patent (U.S. Patent Number 5,001,161) that cover Toprol-XL are invalid. The Court also found that the patents asserted by AstraZeneca in the litigation are unenforceable.

This case is a consolidation of the company's cases against defendants KV Pharmaceutical Company, Andrx Pharmaceuticals LLC, Andrx Corporation, and Eon Labs Manufacturing Inc.

AstraZeneca maintains that both patents are valid and enforceable and will appeal the Court's decision. Both patents are due to expire on September 17th 2007, informs the company release/

Sales for Toprol-XL in the US in 2005 were $1,291 million. Toprol-XL is a registered trademark of the AstraZeneca group of companies.

Toprol-XL is a beta1-selective (cardioselective) adrenoceptor-blocking agent, for oral administration, available as extended-release tablets.