Aug. 4 (Bloomberg) -- Bayer AG, Germany's largest drugmaker, sued Novartis AG's Sandoz unit to prevent it from selling a copy of the Yaz birth-control pill in the U.S.

Sandoz, the world's second-biggest maker of generic drugs, is seeking U.S. Food and Drug Administration approval to sell a copy of Yaz. According to complaints filed Aug. 1, Bayer wants a federal judge in Denver or Las Vegas to block that approval until two patents on the medicine expire in 2014.

Bayer, based in Leverkusen, Germany, needs to protect Yaz from generic competition because a judge invalidated a patent on a related pill, Yasmin, in a dispute with Barr Pharmaceuticals Inc. Bayer cut the 2008 profit goal for its health-care unit and last month signed an agreement to allow Barr to distribute Yasmin under its own label in an effort to retain sales.

Yaz and Yasmin are part of a group of birth-control products that brought in 1.04 billion euros ($1.6 billion) last year for Bayer. Sandoz and other generic-drug makers also were sued over their plan to sell copies of Yasmin. Bayer is appealing the judge's invalidity ruling on a patent that expires in 2011.

In its FDA application to sell generic Yaz, Sandoz said the patents are invalid, according to Bayer. Sandoz spokeswoman Lauren Carhart said the company doesn't comment on litigation. The complaints filed in Denver and Las Vegas are identical, and the courts will decide where the case should be heard.

Teva Pharmaceutical Industries Ltd. is the world's biggest generic-drug maker.

The cases are Bayer Schering Pharma AG v. Sandoz Inc., 08cv995, U.S. District Court, District of Nevada (Las Vegas) and Bayer Schering Pharma AG v. Sandoz Inc., 08-1638, U.S. District Court, District of Colorado (Denver).

To contact the reporter on this story: Susan Decker in Washington at sdecker1@bloomberg.net.

Last Updated: August 4, 2008 18:59 EDT