Divalproex Sodium Versus Valproic Acid in Hospital Treatment of Psychotic Disorders

Background: Approximately 50% of pharmacy prescriptions in the United States are filled with generic drugs, which have improved substantially in quality owing to increased governmental regulations. The remaining medicoeconomic question regards whether or not brand-name medications are worth the price. This study evaluates these questions for the brand-name mood stabilizer divalproex sodium and its generic counterpart, valproic acid.

Method: We conducted a retrospective chart review of all patients who had been taking divalproex and had been switched to valproic acid at 2 local mental health facilities in 1997. Data collected from the inpatient- and day-treatment charts for these 28 patients included dose, duration, side effects, and efficacy (determined using retrospective chart review and the Clinical Global Impressions scale [CGI]) of divalproex sodium compared with valproic acid treatment.

Results: t Tests for dependent samples revealed that valproic acid was administered at higher doses than divalproex sodium, but these treatments did not differ in efficacy on the basis of CGI scores. Fisher exact test analyses revealed a trend toward more nausea with valproic acid; also, the combination of nausea, abdominal discomfort, and diarrhea occurred more often in valproic acid treated patients. There were no differences in the discontinuation of either medicine because of side effects, or in the use of medications to treat gastrointestinal side effects. Efficacy was similar for valproic acid and divalproex sodium. There was no single, significant side effect increase for valproic acid; however, when grouped together, gastrointestinal side effects were statistically significantly increased in valproic acid treated patients. This appears clinically insignificant because of the lack of difference in drug discontinuation rate or gastrointestinal medication use.

Conclusion: Given these results and that valproic acid is much less expensive than divalproex sodium, valproic acid appears to be a satisfactory substitution for divalproex sodium in the treatment of frequently hospitalized psychotic patients.