• - Adverse events at every visit - Abnormality of clinical laboratory test values at Week0, Week6, Week16, Week28, Week 40 and Week 52 - Vital signs at every visit - Electrocardiogram at Week0, Week6, Week28 and Week 52
  

• - CGI-S at every visit - HAM-D at Week0, Week6, Week16, Week28, Week 40 and Week 52 - YMRS at Week0, Week6, Week16, Week28, Week 40 and Week 52 - Serum lamotrigine concentrations at Week6, Week16, Week28, Week 40 and Week 52 [ Time Frame: Week 52 ]
  
• Change from baseline of Clinical Global Impressions of Severity (CGI-S); Change from baseline of Hamilton Depression Rating Scale (HAM-D); Change from baseline of Young Mania Rating Scale (YMRS);
  

Inclusion Criteria:

• Of subjects participating in the preceding double-blind study, those who are judged by the investigator/sub-investigator to have well tolerated the double-blind treatment and to be eligible for the 52-week extension treatment
• Sex: either sex. Female of child-bearing potential will be eligible for inclusion in this study. However they have to have a negative pregnancy test at the start of this study, agree to further pregnancy testing at the time points determined in study assessments and procedures and practice one of the following methods of contraception from the start of this study until the end of the follow-up examination:

Abstinence

Oral contraceptive, either combined or progestogen alone (except during the Dosage Adjustment Phase)

Injectable progestogen

Implants of levonorgestrel

Estrogenic vaginal ring (except during the Dosage Adjustment Phase)

Percutaneous contraceptive patches (except during the Dosage Adjustment Phase)

Intrauterine device (IUD) or intrauterine system (IUS) that meets the SOP effectiveness criteria as stated in the product label

Male partner sterilization (vasectomy with documentation of azoospermia) prior to the female subject's entry into the study, and this male is the sole partner for that subject

Double barrier method: condom or occlusive cap (diaphragm or cervical / vault caps) plus spermicidal agent (foam / gel / film / cream / suppository)

• In/Out patient: Either
• Informed consent: the subject capable of giving written informed consent

Exclusion Criteria:

• Has a score of 3 or more on item of the HAM-D related to suicide or is at a high suicidal risk in the judgment of the investigator/sub-investigator
• Has a history of severe rash or rash due to anti-epileptic drugs
• Patients with severe hepatic/renal/cardiac/pulmonary disorder or hematopoietic disorder. The severity refers to Grade 3 according to "the Classification of the Severity of Adverse Experiences" (PAB/SD Notification No. 80, dated 29 June 1992)
• Patients have less than 5 years of remission history from clinically significant malignancy (other than e.g. basal cell or squamous cell skin cancer, in-situ carcinoma of cervix or prostate CA in situ)
• Patients with chronic hepatitis typeB and /or typeC which is positive of hepatitis B surface antigen （HBsAg）and/or hepatitis C antibody
• Has an acute or chronic illness likely to impair drug absorption, distribution, metabolism or excretion or has any unstable physical symptoms likely to require hospitalisation during participation in the study
• Female patients who are pregnant or lactating, who may be pregnant, or who plan for pregnancy during the study
• Has a history or current diagnosis of epilepsy
• Has received an investigational drug within 30 days of screening
• Patients with a history of drug allergy to any ingredient of the test-drug
• Patients whom the investigator or sub-investigator considers ineligible for the study