Improved CNS tolerability following conversion from immediate- to extended-release carbamazepine

Acta Neurol Scand. 2004 Jun;109(6):374-7. doi: 10.1111/j.1600-0404.2004.00291.x.


Objectives: Tolerability of 'narrow therapeutic ratio' (NTR) antiepileptic drugs may improve with uniform drug delivery. We determined whether conversion from immediate-release carbamazepine (IR-CBZ) to extended-release carbamazepine (ER-CBZ) decreased the incidence of CNS side-effects associated with drug concentration oscillations.

Methods: We compared CNS side effects and seizure frequency for patients with partial-onset seizures (n = 61) treated with IR-CBZ for > or =1 year with conversion to ER-CBZ for > or =1 year. We compared tolerability findings with absorption variability of the formulations.

Results: Incidence of CNS side-effects decreased from 49% during IR-CBZ treatment to 20% following conversion to ER-CBZ. Patients also had improved tolerability of high doses (> or =1200 mg/day) during ER-CBZ treatment. Pharmacokinetic analysis showed absorption and drug concentration were much more variable for the immediate-release formulation.

Conclusions: This study suggests that ER-CBZ formulations, with smoother drug delivery and less variable absorption, provide improved CNS tolerability compared with immediate-release formulations.

Publication types

  • Clinical Trial
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adolescent
  • Adult
  • Aged
  • Anticonvulsants / administration & dosage*
  • Anticonvulsants / adverse effects*
  • Anticonvulsants / pharmacokinetics
  • Carbamazepine / administration & dosage*
  • Carbamazepine / adverse effects*
  • Carbamazepine / pharmacokinetics
  • Delayed-Action Preparations
  • Epilepsy / drug therapy*
  • Female
  • Humans
  • Male
  • Middle Aged
  • Treatment Outcome


  • Anticonvulsants
  • Delayed-Action Preparations
  • Carbamazepine