Clinical and economic impact of replacing divalproex sodium with valproic acid.

The impact of replacing divalproex sodium with valproic acid on patient outcomes and direct drug costs was studied. Before-and-after medical chart review was performed in a state-supported facility for mentally retarded adults in which a pharmacy and therapeutics (P&T) committee recommended replacement of divalproex with valproic acid. Patients were studied if they had received divalproex for at least three months and if their antiepileptic drug was changed from divalproex to valproic acid between October 1993 and June 1994. Clinical, economic, and prescribing-pattern data were recorded for the periods extending 12 months before and 18 months after the change in therapy. Data for 46 patients were analyzed. Replacing divalproex with valproic acid was effective in 41 (89%) of the patients. There was no significant difference between the divalproex and valproic acid periods in seizure rate or frequency of new drug therapy for GI disorders. Between fiscal year 1992-93 and fiscal year 1995-96 there was a 56% decrease in total direct divalproex plus valproic acid costs, including drug products and packaging materials and labor. The rate of valproic acid prescriptions increased steadily after the replacement was recommended, and then plateaued. Replacing divalproex sodium with valproic acid in a group of institutionalized mentally retarded adults with epilepsy was clinically effective and economically advantageous.