Ketamine is an N-methyl-D-aspartate (NMDA) receptor antagonist that has antidepressant and antisuicidal effects, as shown by multiple studies done over the past two decades, that can be used effectively in the management of treatment-resistant depression (TRD). The United States Food and Drug Administration has approved intranasal (S)-ketamine in combination with an oral antidepressant for TRD....