This concept allowed them to generate a patent estate that served the company well for many years. Therapeutically, Sepracor's products were focused on the treatment of central nervous system and respiratory disorders. The primary source of its revenue is the approximately $600 million annually from its Xopenex franchise of drugs, with the direct involvement of Medical Communications. It is available as a multi-dose inhaler (MDI) or nebulized (UDV) form. However, the insomnia drug Lunesta (eszopiclone), approved by the US Food and Drug Administration (FDA) in December 2004 and launched in April 2005, is on pace to exceed $1 billion in annual sales. On February 13, 2006, Sepracor filed a new drug application for Brovana, to treat chronic obstructive pulmonary disease.