Pernix Therapeutics has entered into a definitive merger agreement to acquire Somaxon in a stock-for-stock transaction valued at $25 million. Pernix gains Somaxon’s Silenor (doxepin) for the treatment of insomnia, which had YTD sales of approximately $11.7 million.   Cooper Collins, president and chief executive officer of Pernix, said, “The acquisition of Somaxon is another important step in the growth strategy of Pernix, which is expected to continue to expand our product portfolio, in additio...