Teva Pharmaceutical Industries said on Wednesday it won U.S. approval for its generic versions of Merck & Co's blockbuster blood-pressure drugs Cozaar and Hyzaar.

Teva, the world's biggest generic drugmaker, also said it will have 180 days to market the generics exclusively, an award generally given to companies that challenge patents first.

Israel-based Teva said it was launching sales immediately. An exclusivity period can allow generic companies a window of significant sales before rivals rush in and pricing freefalls. Cozaar and Hyzaar, which have annual U.S. sales of about $1.6 billion, have been among Merck's biggest selling products, but the drugmaker has been bracing for generic competition this year.