The purpose of this study is to determine the safety and effectiveness of Depakote ER compared to placebo in the treatment of bipolar disorder, manic or mixed type in adults.

INCLUSION CRITERIA

• Current primary diagnosis of bipolar I disorder, mania or mixed type
• Acute exacerbation of mania associated with bipolar disorder as defined by Mania Rating Scale score >= 18
• Hospitalized no more than 7 days at time of Screening or in process of being admitted
• History of at least one prior manic or mixed episode within past 3 years, exclusive of the current episode. Prior manic or mixed episode must be separated from current episode by at least 2 months of sustained improvement

EXCLUSION CRITERIA

• History of schizophrenia or schizoaffective disorder
• Axis I (e.g., anxiety disorder), or Axis II (e.g., personality disorder) that would interfere with compliance or confound interpretation of study results
• Current manic or mixed episode is drug-induced or secondary to a medical disorder (e.g., AIDS, corticosteroids)
• Current manic or mixed episode is believed to be caused by antidepressant use (i.e., antidepressant-induced mania)
• Had first manic episode after age 60
• Has ever taken clozapine
• Has received depot neuroleptic medication within one inter-injection interval of first dose of study drug
• Urine toxicology screen is positive for phencyclidine (PCP), opiates, cocaine or amphetamines
• History of active alcohol or substance dependence within past 3 months.
• History of failed treatment on adequate valproate therapy for bipolar disorder
• Has taken Depakote (DR or ER) regularly over the last 30 days
• Has serious violent, homicidal, or suicidal ideation