Differential effectiveness between Ketamine and Esketamine: the predictive role of dissociative features. A treatment-resistant depression case.

More than 10 years ago, the discovery of the antidepressant effects of Ketamine opened the opportunity to develop a novel class of antidepressants. Ketamine induces dissociative symptoms as a major side effect. This rapid-acting antidepressant is available as an endovenous racemic compound and as an intranasal S-enantiomer: Esketamine; which is four-fold more potent for the NMDA receptor. Here we present the critical case of a patient who took both molecules experiencing remission just with endovenous Ketamine, whose impact in terms of dissociative symptoms was greater. In this short report, we discuss the differences between the two drugs and the possibility of dissociative features to predict their efficacy.