Merck has entered an agreement to begin development of a Zetia and Lipitor combination product in collaboration with Schering-Plough. The Merck/SP Pharmaceuticals joint venture was formed in 2000 to develop and market new medicines in the U.S. in cholesterol management and respiratory disease. The cholesterol collaboration was expanded in 2001 and includes worldwide markets (excluding Japan). The joint venture/partnership also markets Zetia and Vytorin in the U.S. (and marketed as Ezetrol and In...