Merck’s blockbuster osteoporosis drug Fosamax will lose patent protection tomorrow with the expiration of Orange Book listed US Patent No. 4,621,077, losing significant $ 1.6 billion US market to generic competition. Earlier in January, Merck announced to sign a deal for an authorized generic but did not disclose the name of its partner. Finally, it is Watson Laboratories that will be selling the authorized version of Fosamax. Barr Pharmaceuticals and Teva Pharmaceutical Industries are also expected to launch generic versions Fosamax this week.