Valproate is one of the largest-selling drugs for bipolar disorder worldwide.

Like other, older, mood stabilizers, the efficacy of valproate is primarily, if not entirely, in the manic pole of the illness.  Studies leading to its regulatory license demonstrated acute efficacy in mania, but to date, there has been no clear demonstration of an effect in the depressive pole of bipolar disorder. 

The current commercial positioning of valproate appears to be reactive, especially to Lilly's positioning efforts with olanzapine. Thus the most recent detail aid for valproate refers to the drug as "foundation therapy you can build on" (suggesting valproate as the base mood stabilizer to which all other drugs can be added) and emphasizes superiority to olanzapine with respect to effects on cholesterol levels.

Strengths:

• Established efficacy in acute mania.
• Long history of use in epilepsy and psychiatry.

Weaknesses:

• Evidence supporting valproate as bipolar maintenance therapy is limited and inconsistent.
• Side effects include somnolence, weight gain, and endocrine changes (including PCOS).
• High propensity for drug-drug interactions.