Ketamine and its S-enantiomer, esketamine, have shown to be promising molecules for use in psychiatry. Widely investigated for the treatment of drug-resistant depression, they could be used in emergency conditions, due to their rapid onset of action, in two main conditions : 1) psychomotor agitation, and 2) acute suicidal ideation and behavior (suicidal crisis). In particular, intranasal administration offers a non-invasive, safe and very easy to administer option. An effect begins a few hours to a day after intake and lasts for about a week. These molecules present an innovative option for the future and their specific use in psychiatric emergencies.