Efficacy of Prazosin in Preventing Post-traumatic Stress Disorder

Inclusion Criteria: * Patient of age \>18 years and \<65 years * Victim of direct experience trauma (accident or physical aggression) * Presence of an ASD between D3 and D7 after the trauma according to DSM V criteria Exclusion Criteria: * Contra-indication to prazosin: orthostatic hypotension, right heart failure, other hypotensive therapy, 5-phosphodiesterase inhibitors (sildenafil) or diuretic, history of syncope or severe unexplained faintness, hypersensitivity known to quinazolines. * Alcohol and / or drug use at the time of the trauma * History of psychotic disorder * Suicidal risk defined by a score ≥ 2 on the Suicidal Ideas Item of the Beck Depression Inventory (BDI) * Protected or vulnerable Major * Persistence of a life threatening injury at D3 * Sexual assault * Only moderate head trauma can be included and therefore excluded patients with loss of consciousness greater than 30 minutes, Glasgow score less than 13, post-traumatic amnesia greater than 24 hours (Ruff et al., 2009) . * Prescription of morphine or morphine derivative in progress * Pregnancy or breastfeeding period * Lack of effective contraception in a woman susceptible to childbearing * Known hepatic dysfunction * Narcolepsy (Gelineau's disease) * Cardiac or vascular history including coronary artery disease * Strict low-sodium diet