Memantine Augmentation of Antidepressants

Inclusion Criteria: Male or female patients between 18 and 85 years of age at screening. Patients must provide written informed consent prior to study entry. Patients must meet DSM-IV-TR (Diagnostic and Statistical Manual IV Text Revision) criteria for Major Depressive Episode of a severity mild, moderate or severe or in partial remission, as confirmed by the MINI. Patients must have a HAM-D (17-item) score of 16 or higher. Patients must have been on 1 of the following medications for 4 or more weeks at or above the listed dose with no psychiatric medication dose changes for the past 25 days: 20 mg qD of fluoxetine (Once Daily) 50 mg qD of sertraline 20 mg qD of paroxetine 200 mg qD of fluvoxamine 20 mg qD of citalopram 10 mg qD of escitalopram 150 mg qD of venlafaxine or venlafaxine sustained release 300 mg qD of bupropion or bupropion sustained or extended release 15 mg qD of mirtazapine 60 mg qD of duloxetine Participants must agree to keep the dose of their existing antidepressant(s) constant throughout the 8-week trial. Exclusion Criteria: Diagnosis of bipolar disorder or schizophrenic or schizoaffective disorder. History of alcohol or drug abuse or dependence within 6 months of enrollment. Patients who have received ECT (Electroconvulsive Therapy) in the past 3 months. History of seizures. Moderate dementia (MMSE score of 20 or less). Active suicidal ideation: endorsing a 3 (most severe score) on QIDS-SR (Quick Inventory of Depression Symptomatology Self Reports) suicide item OR a score of 2 or higher for the past week on Suicide Scale items 4 or 5 (current suicidal ideation moderate or strong or would avoid taking steps to save life). Currently taking a mood stabilizer or antipsychotic (except lithium clearly used as an augmenting agent). Patients who, in the opinion of the investigator, might not be suitable for the study.