Inclusion Criteria:

1. Subjects must be between ages 18 and 70.
2. Subjects must meet DSM-IV criteria for bipolar disorder confirmed by the Mini International Neuropsychiatric Interview (MINI).
3. Subjects must be taking at least one medication for mania at a therapeutic dose for at least 2 weeks.
4. Subjects must have been diagnosed with bipolar disorder, type 1, for at least 2 years prior to baseline.
5. Subjects must have adequate response to medications as evidenced by Young Mania Rating Scale (YMRS) score less than or equal to 10 at screening and at baseline.
6. Subjects must have adequate response to medications as evidenced by Hamilton Depression Rating Scale (HAM-D) score less than or equal to 10 at screening and at baseline.
7. Subjects must have had at least 1 manic episode in the 2 year period prior to entering the study.
8. Female subjects must be either postmenopausal for at least 1 year, surgically sterile, abstinent or practicing an effective method of birth control if sexually active. Acceptable methods of birth control during this study are regular use of contraceptive pills, intra-uterine devices, barrier methods or abstinence. Female subjects must also have a negative urine pregnancy test at screening, baseline and other time points throughout the study.
9. Subjects must be able and willing to comply with self-administration of medication or have consistent help/support available.
10. Subjects must have signed an informed consent document indicating that they understand the purpose of and procedures required for the study and are willing to participate in the study.
11. Subjects must be able and willing to meet or perform study requirements (e.g. answer self-administered questionnaires).
12. Subjects must be willing to allow study staff to contact subject's regular psychiatrist while the subject is in the study.

Exclusion Criteria:

1. Subjects who are unable to provide informed consent.
2. Subjects with a serious, unstable medical illness (such as cardiovascular, respiratory, neurologic, hematologic, renal, hepatic, endocrine, immunologic, or other systemic illness), a history of cerebrovascular disease, uncontrolled diabetes mellitus or AIDS. Subjects with chronic illness must be stable and otherwise physically healthy on the basis of a physical examination, medical history, electrocardiogram and the results of blood biochemistry, hematology tests and a urinalysis.
3. Subjects who develop a medical condition during participation which can affect mood stability (i.e. seizure disorder, brain tumors, brain trauma, stroke, multiple sclerosis, etc.)
4. Subjects who develop substance abuse or dependence during participation in the study.
5. Subjects taking azathioprine, mercaptopurine, apalcillin, and/or amoxicillin.
6. Subjects who have been intoxicated with alcohol or drugs within the last 72hrs.
7. Subjects with a history of severe pre-existing gastrointestinal narrowing or inability to swallow oral study medication whole with the aid of water.
8. Female subjects who are pregnant or nursing.
9. Subjects who have previously participated in this study.
10. Subjects with an anticipated life expectancy of 6 months or less.
11. Subjects who have received an experimental drug or used an experimental medical device within 1 month of screening.