Nebulized Ketamine for the Treatment of Major Depressive Disorder

Inclusion Criteria:

* All individuals 18 years and older with a Montgomery-Asberg Depression Rating Scale score (MADRS) ≥ 20
* Must have a diagnosis of moderate to severe Major Depressive Disorder (MDD)
* Structured Clinical Interview for DSM-5 (SCID-5) will be performed to confirm MDD diagnosis

Exclusion Criteria:

* Adult patients with an allergy to Ketamine
* Adult patients with an allergy to Midazolam
* Individuals with a history of mania/hypomania or diagnosis of bipolar disorder
* Patients on lithium and/or lamotrigine therapy
* Recent or current homicidal ideation with an intent to act
* MDD with psychotic features or current or past diagnosis of a psychotic disorder
* No substance use disorder in the preceding 3 months except nicotine or caffeine or a positive urine screen for substances (except cannabis)
* Diagnosis of obsessive-compulsive disorder, antisocial personality disorder, borderline personality disorder, posttraumatic stress disorder, intellectual disability, altered mental status, pregnant or breastfeeding patients,
* Patients on \> 2 medications for hypertension
* Patients with uncontrolled hypertension (BP \>140 mm Hg systolic and/or \>90 mm Hg diastolic on two separate readings at the time of screening)
* Body weight of \> 150kg
* Patients with history of congestive cardiac failure
* Day of presentation, patients with unstable vital signs (systolic blood pressure \<90 or\>160 mm Hg, pulse rate \<50 or \>150 beats/min, and respiration rate \<10 or \>30 breaths/min)
* Consumption of opioids within 24 hours of drug administration
* Acutely intoxicated patients will also be excluded