Nebulized Ketamine for the Treatment of Major Depressive Disorder

This study tests whether nebulized (inhaled mist) ketamine — given in a low dose through a breathing mask — is a safe and effective treatment for hospitalized patients with moderate to severe major depressive disorder (MDD). **You may be eligible if...** - You are 18 or older and currently hospitalized in a psychiatric unit - You have a confirmed diagnosis of moderate to severe major depression (MDD) - Your depression score on a standard rating scale is 20 or above **You may NOT be eligible if...** - You have an allergy to ketamine or midazolam - You have bipolar disorder (history of mania or hypomania) - You have a psychotic disorder (including MDD with psychotic features) - You have a substance use disorder (other than nicotine or caffeine) in the past 3 months - You have PTSD, OCD, borderline or antisocial personality disorder, or intellectual disability - You have uncontrolled high blood pressure or congestive heart failure - You weigh more than 150 kg - You are currently on lithium or lamotrigine, or on more than 2 blood pressure medications - You are pregnant or breastfeeding Talk to your doctor to see if this trial is right for you.