• Improvement of scores on Hamilton Depression Rating Scale and Clinical Global Improvement Scale given once a week for eight weeks [ Time Frame: 8 weeks ] [ Designated as safety issue: No ]
• Improvement of scores on Selective Reminding Test, Digit Span Test, Stroop Test, and Trail Making Test [ Time Frame: given every other week for 8 weeks ] [ Designated as safety issue: No ]

• Improvement of scores on Hamilton Depression Rating Scale and Clinical Global Improvement Scale given once a week for eight weeks
• Improvement of scores on Selective Reminding Test and Trail Making Test
• Scales given every other week, for eight weeks

The purpose of this study is to investigate whether addition of memantine to bipolar depression patients who have had an incomplete response to lamotrigine (Lamictal) which is frequently used to treat bipolar depression in the clinical setting. At present, memantine is approved for use in the treatment of Alzheimer's disease or dementia, but not for use for the treatment of bipolar depression. Subjects will be asked to participate because they are suffering from bipolar depression associated and have had an inadequate response to lamotrigine. Subjects will have to be on at least 100 mg per day, for at least 4 weeks.

Hypothesis/Objectives:

H1: Lamotrigine inadequate-response patients augmented with memantine for 8 weeks will have significantly greater improvement on the Hamilton Depression Rating Scale (HDRS) and Clinical Global Improvement (CGI) scale compared to patients augmented with placebo.

H2: Lamotrigine inadequate-response patients augmented with memantine for 8 weeks will have significantly greater improvement of scores on the Selective Reminding Test (SRT), the Digit Span Test, the Stroop Test, and Trail Making Test (TMT) than patients augmented with placebo.

Study Population:

We will study 40 bipolar disorder depressed (BDD) outpatients (20 in each arm) recruited from the outpatient Mood Disorders Clinic and by advertisement.

• Drug: Memantine
• Drug: Placebo

• Placebo Comparator: Placebo daily
• Active Comparator: Daily dose Memantine

Inclusion Criteria:: 1) age 18 - 65; 2) satisfy DSM-IV-TR criteria for Bipolar Disorder and Major Depressive Episode; 3) Lamotrigine Inadequate-Response: Defined as already treated with at least 100 mg of lamotrigine for at least 4 weeks but 17 item HDRS rating > 15; 4) give informed consent as approved by local IRB; 5) if on other antidepressants or mood stabilizers on stable dose for the past 4 weeks.

Exclusion Criteria:1) comorbid psychotic disorder such as schizophrenia or schizoaffective disorder; 2) significant suicidal or homicidal risk; 3) clinically significant medical illness; 4) allergy or intolerance to lamotrigine or memantine; 5) pregnancy, planning to be pregnant or not using adequate contraception; 6) satisfy criteria for substance dependence within 6 months prior to start of the study; and 7) on any medication with significant adverse interaction with either lamotrigine or memantine.