After a traumatic event such as an accident or an assault, victims may experience intense stress symptoms that may evolve into "post-traumatic stress disorder" (PTSD). It is a frequent and serious pathology, which can be complicated by depression, addiction or suicide. Few means are available to prevent PTSD in people who have just undergone trauma. Prazosin is an antihypertensive drug that blocks α1 adrenaline receptors which could help to stop the vicious circle of stress and prevent the development of the disease. The objective of this study is to demonstrate the efficacy of prazosin to prevent PTSD in patients who visit an emergency department after trauma.

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