X0303 4 2009-12-10 0001339455 Somaxon Pharmaceuticals, Inc. SOMX 0001013425 TREU JESSE I C/O DOMAIN ASSOCIATES, L.L.C. ONE PALMER SQUARE PRINCETON NJ 08542 1 0 0 0 Common Stock 2009-12-10 4 S 0 56891 1.15 D 1245161 I By Domain Partners VI, L.P. Common Stock 2009-12-10 4 S 0 609 1.15 D 14131 I By DP VI Associates, L.P. Common Stock 2009-12-11 4 S 0 403675 1.15 D 841486 I By Domain Partners VI, L.P. Common Stock 2009-12-11 4 S 0 4325 1.15 D 9806 I By DP VI Associates, L.P. The Reporting Person is a managing member of One Palmer Square Associates VI, L.L.C., which is the sole general partner of Domain Partners VI, L.P. and DP VI Associates, L.P. Pursuant to Instruction 4(b)(iv) of Form 4, the Reporting Person has elected to report as indirectly beneficially owned the entire number of securities beneficially owned by each such entity. The Reporting Person disclaims beneficial ownership of any securities, and any proceeds thereof, that exceed his or her pecuniary interest therein and/or that are not actually distributed to him or her. The Reporting Person also directly beneficially owns 43,174 shares of Common Stock (represented by restricted stock units) and indirectly beneficially owns 19,166 shares of Common Stock held by Domain Associates, L.L.C. and 61,308 shares of Common Stock held by One Palmer Square Associates VI, L.L.C. The Reporting Person is a managing member of Domain Associates, L.L.C. Pursuant to Instruction 4(b)(iv) of Form 4, the Reporting Person has elected to report as indirectly beneficially owned the entire number of securities beneficially owned by such entity. The Reporting Person disclaims beneficial ownership of any securities, and any proceeds thereof, that exceed his or her pecuniary interest therein and/or that are not actually distributed to him or her. /s/ Kathleen K. Schoemaker, Attorney-in-Fact 2009-12-14