Conversion from delayed-release sodium valproate to extended-release sodium valproate: initial results and long-term follow-up

Epilepsy Behav. 2006 May;8(3):601-5. doi: 10.1016/j.yebeh.2006.02.006.


Objective: The goal of our study was to evaluate clinical and serum valproic acid concentration changes in patients following overnight conversion from delayed-release sodium valproate (VPA-DR) to the same daily dosage of extended-release sodium valproate (VPA-ER).

Methods: Epilepsy patients on VPA-DR were offered the chance to convert to VPA-ER. Thirty patients were converted to twice-daily dosing and 11 were converted to once-daily dosing. Trough levels of valproic acid were measured prior to the change and 2 weeks after conversion. Short-term and long-term clinical data were evaluated.

Results: Patients successfully converted from VPA DR to VPA-ER. No significant difference in percentage change in serum trough valproic acid level was observed when comparing dosing frequency of VPA-DR, total daily dosage of VPA, conversion to once-daily versus twice-daily VPA-ER, or presence of enzyme-inducing agents. Mean seizure count per month prior to conversion was 3.35 versus 3.29 following conversion. Improvements in tremor, weight gain, and nausea/vomiting were noted.

Conclusions: Overnight conversion to VPA-ER was well tolerated by all patients. Long-term results were favorable, with 77.5% of patients remaining on drug. Seizure counts and adverse events remained the same or were improved in both short-term and long-term evaluations. Dosing of VPA-ER either once-daily or twice-daily is acceptable.

Publication types

  • Clinical Trial

MeSH terms

  • Anticonvulsants / administration & dosage*
  • Anticonvulsants / adverse effects
  • Anticonvulsants / pharmacokinetics
  • Delayed-Action Preparations / adverse effects
  • Delayed-Action Preparations / pharmacokinetics
  • Epilepsy / drug therapy*
  • Follow-Up Studies
  • Humans
  • Patient Compliance
  • Valproic Acid / administration & dosage*
  • Valproic Acid / adverse effects
  • Valproic Acid / pharmacokinetics
  • Weight Gain / drug effects*


  • Anticonvulsants
  • Delayed-Action Preparations
  • Valproic Acid