Valproate is widely used as a mood stabiliser for people with bipolar disorder, despite the fact that there is very little evidence that shows the effectiveness of this treatment.

This observational cohort study looked at over 4,000 bipolar patients in Denmark who were treated with lithium or valproate from 1995 to 2006.

The results favoured lithium:

• The rate of switch/add on to the opposite drug (lithium or valproate), antidepressants, antipsychotics or anticonvulsants (other than valproate) was increased for valproate compared with lithium (hazard ratio (HR) = 1.86, 95% CI 1.59-2.16).
• The rate of psychiatric hospital admissions was increased for valproate v. lithium (HR = 1.33, 95% CI 1.18-1.48) and regardless of the type of episode leading to a hospital admission (depressive or manic/mixed).
• For participants with a depressive index episode (HR = 1.87, 95% CI 1.40-2.48), a manic index episode (HR = 1.24, 95% CI 1.01-1.51) and a mixed index episode (HR = 1.44, 95% CI 1.04-2.01), the overall rate of hospital admissions was significantly increased for valproate compared with lithium.

The authors concluded that:

In daily clinical practice, treatment with lithium seems in general to be superior to treatment with valproate.

Kessing LV, Hellmund G, Geddes JR, Goodwin GM, Andersen PK. Valproate v. lithium in the treatment of bipolar disorder in clinical practice: observational nationwide register-based cohort study. Br J Psychiatry. 2011 May 18. [Epub ahead of print] [PubMed abstract]