Iloperidone for Symptoms of Arousal in Post Traumatic Stress Disorder (PTSD)

During Period A, subjects will receive 8 weeks of iloperidone or placebo (2 weeks titration period followed by 6 weeks on stable dose). Then they will be reassessed for response during Period A; study drug will be discontinued and washed out over the following 2 weeks. They will then begin Period B on the alternate blinded treatment with similar titration and assessment, initially weekly and then every other week for a total of another 8 weeks. The purpose of the study is to determine whether Iloperidone is effective in the treatment of some symptoms in patients with PTSD, particularly difficulty falling or staying asleep, trauma dreams and daytime irritability or outbursts.