 In the last few years, considerable attention has been dedicated to the glutamate system as a possible contributor of the antidepressant response. The most striking breakthrough has been the rapid antidepressant response of intravenous ketamine using doses that are about a quarter of the routinely utilized anesthetic dose in children and adults.5,6 Unlike many anesthetic agents, ketamine does not depress cardiovascular and respiratory parameters.7 The primary action of ketamine is to block N-Methyl-D-Aspartate NMDA receptors. The antidepressant response to ketamine often manifests itself within a few hours, but is generally maximal after 24 hours.8 Importantly, a single infusion produces in the most subjects a robust decrease of suicidal ideation.9,10 The drawback of this approach is, however, that its benefits generally disappear within a week.6 Consequently, much clinical work remains to be carried out in order to better understand and maintain the antidepressant response of ketamine. 