Valeant Pharmaceuticals has entered into a definitive agreement to acquire all outstanding common stock of Obagi Medical Products, Inc. for approximately $360 million in cash. The transaction is expected to close in 1H13 and to yield cost synergies of $40 million within six months of closing.   Obagi is a provider of topical aesthetic and therapeutic skin-health systems with a portfolio that includes dermatology brands Obagi Nu-Derm, Condition & Enhance, Obagi-C Rx, ELASTIDerm and CLENZIDerm...