Intramuscular Ketamine for Suicidal Ideation

Inclusion Criteria: * Current clinically significant suicidal ideation, defined as a score of \> or = 4 on the MADRS item 10 and a positive answer on items 3,4 or 5 of the C-SSRS. * Inpatient status at the time of study initiation. * 18 to 70 years of age * Capacity to consent Exclusion criteria: * Diagnosis of a primary psychotic disorder (e.g., schizoaffective disorder) * Diagnosis of pervasive developmental disorder * Diagnosis of a major neurocognitive disorder * A positive urine pregnancy test * Currently breastfeeding * Drug or alcohol abuse or dependence within the preceding 3 months; a rather narrow time period was chosen, however, in order to allow participation by individuals with a history of substance abuse or dependence problems that could be secondary to their SI, and to more closely approximate patients seen in real-world settings. Given the increasingly widespread use of marijuana, and in an effort to recruit a naturalistic study population, concurrent marijuana use is not an exclusion criterion, as long as they are not actively intoxicated. * Current positive UTOX for amphetamine, benzodiazepines, cocaine, opiates (if not prescribed) * Medical issues or laboratory abnormalities requiring acute intervention * Patients for whom an increase in blood pressure or intracranial pressure would pose a serious risk (e.g., aneurysmal vascular disease, arteriovenous malformation, history of intracerebral hemorrhage, unstable angina) * Any lifetime history of ketamine or phencyclidine abuse * A known hypersensitivity to or history of a serious adverse effect from to ketamine