The probability of response after each subcutaneous injection of esketamine in treatment-resistant depression.

Introduction: The administration of multiple esketamine doses has shown efficacy for unipolar and bipolar treatment-resistant depression (TRD). Nevertheless, the probability of responding or not after each dose in the real-world remains unknown. This study aimed to estimate it throughout four doses of esketamine, administrated via subcutaneous (SC).

Material And Methods: We conducted a retrospective analysis of a case series of 70 patients with TRD who received treatment from the esketamine assistance program at Federal University of Sao Paulo, between April 2017 and December 2018. The SC injections were administrated weekly at a dose of 0.5-1.0mg/kg, in conjunction with patients' psychotropic drugs. Response was defined as a decrease of at least 50% in the Montgomery-Åsberg Depression Rating Scale between baseline and 24h after dose. We used hidden Markov modeling in order to estimate de probability of response after each esketamine injection.

Results: The probability of a patient that was a "non-responder" to become a "responder" following a SC injection of esketamine was 17.30% and the probability that this patient remains a "non-responder" was 82.70%. The probability of a patient that was a "responder" to remain as a "responder" was 95%.

Conclusions: Patients with TRD who had not responded after the first dose of esketamine, still had a chance of responding after the subsequent dose administrated via SC.