Nepicastat for Posttraumatic Stress Disorder (PTSD) in OIF/OEF Veterans

HYPOTHESES Primary Hypothesis: Compared to placebo treatment, nepicastat-treated OIF/OEF veterans with PTSD will have significantly reduced PTSD hyperarousal symptoms as defined by the Clinician Administered PTSD Scale \[CAPS\], subscale D (CAPS-D). Secondary Hypotheses: Compared to placebo, nepicastat-treated OIF/OEF veterans with PTSD will have: * Significantly reduced PTSD symptoms (total CAPS) * Significantly reduced PTSD reexperiencing symptoms (CAPS-B) * Significantly reduced PTSD avoidance symptoms (CAPS-C)