Ketamine in the Treatment of Suicidal Depression

INCLUSION CRITERIA:

* Unipolar depression with current major depressive episode (MDE). Participants may be psychiatric medication-free, or if on psychiatric medication, not responding adequately given current MDE with suicidal ideation (See 2).
* Moderate to severe suicidal ideation
* 18-65 years old
* Participants must agree to a voluntary admission to an inpatient research unit at the New York State Psychiatric Institute (NYSPI)for the infusion(s), for a brief stay, or longer if clinically necessary.
* Pre-menopausal female participants of child-bearing potential must be willing to use an acceptable form of birth control during study participation such as condoms, diaphragm, or oral contraceptive pills.
* Able to provide informed consent
* Participants 61-65 years old must score a 25 or higher on the Mini-Mental State Examination (MMSE) at screening.

EXCLUSION CRITERIA:

* Unstable medical condition or neurological illness, including baseline hypertension (BP\>140/90) or significant history of cardiovascular illness.
* Significant ECG abnormality
* Pregnant or lactating
* Diagnosis of bipolar disorder or psychotic disorder
* Contraindication to any study treatment.
* Inadequate understanding of English.
* Prior ineffective trial of or adverse reaction to Ketamine or Midazolam.
* Opiate use greater than total daily dose of 20mg Oxycodone or equivalent during the 3 days pre-infusion.
* A diagnosis of sleep apnea.