Evaluation of the Efficacy and Safety of Subcutaneous Ketamine in the Treatment of Depressive Episode With Suicidal Ideation and/or Behavior in Adolescents

Inclusion Criteria: * Age between 12 and 19 years. * Diagnosis of Major Depressive Episode, unipolar, made through the Schedule for Affective Disorders and Schizophrenia for School-Age Children (K-SADS-PL) administered by experienced evaluators, using DSM-5 criteria. * Under usual treatment for Major Depressive Episode, including clinically indicated psychopharmacological treatment and/or psychosocial treatment at one of the two collaborating clinics (DICA and Conversas de Vida / Unifesp). * Score ≥ 25 on the MADRS (Montgomery-Åsberg Depression Rating Scale). * Score ≥ 28 on the CDRS (Children Depression Rating Scale). * Score ≥ 2 on the Columbia Suicide Severity Rating Scale (C-SSRS). * History of suicide attempt or significant suicidal ideation or planning with a plan or intention requiring emergency evaluation in the last 30 days. Exclusion Criteria: * Presence of the following psychiatric comorbidities: Autism Spectrum Disorder, Bipolar Disorder, Schizophrenia, Schizoaffective Disorder, or psychiatric disorder secondary to physical illness, and history of ketamine or other substance abuse or dependence in the last 6 months. * Presence of Intellectual Disability (assessed by IQ testing). * Presence of the following clinical comorbidities: history of myocardial infarction, congenital heart disease, decompensated cardiac arrhythmia, decompensated hypertension, porphyria, stroke, brain trauma with loss of consciousness, intracranial hypertension, hydrocephalus, central nervous system tumors, or central nervous system abnormalities. * Previous treatment for depression with esketamine. * Allergy to esketamine. * If female: pregnancy or breastfeeding.