Lower Effectiveness of Divalproex Versus Valproic Acid in a Prospective, Quasi-Experimental Clinical Trial Involving 9,260 Psychiatric Admissions

Lower peak valproate concentrations with divalproex sodium may have enhanced tolerability but may also explain the lower effectiveness. Extended-release divalproex could lower effectiveness further and require higher doses. Thus, inpatients are better served by beginning with generic valproic acid and by changing to delayed-release divalproex only if intolerance occurs. This would save up to one-third of inpatient costs and two-thirds of a billion dollars yearly in medication costs.