A total of 250\~300 male and female subjects from the Department of Psychiatry at National Cheng Kung University Hospital. Eligible subjects who are aged between 18\~65 years old and clinically suspected of having bipolar II disorder are invited. The add-on double-blind study treatment with dextromethorphan/place will commence at randomization for while patients continue open-label valproate. Subjects will be enrolled for 12 weeks double-blind add-on treatment and randomly assigned to (1) 30mg dextromethorphan+valproate, (2) 5mg memantine+valproate, (3) dextromethorphan+memantine+valproate or (4) placebo+valproate. Concomitant benzodiazepine medication (preferably up to 8mg lorazepam) may be used for daytime sedation, agitation or insomnia during the study. For the consideration of the less influence to immune-system, resperidone 1-3mg/daily and fluoxetine maximum 20mg/daily will be chose. We will measure the treatment response and side effect to clarify the curative effect of DM and memantine add-on therapy to valproate in the treatment of bipolar disorders. This study is being performed to investigate the possibly significant beneficial effects on the subtypes of bipolar disorders psychopathology.
