Clinical Pharmacokinetics

, Volume 43, Issue 12, pp 763–780 | Cite as

Pharmacokinetic Interactions of Topiramate

  • Meir Bialer
  • Dennis R. Doose
  • Bindu Murthy
  • Christopher Curtin
  • Shean-Sheng Wang
  • Roy E. Twyman
  • Stefan Schwabe
Review Article


Topiramate is a new antiepileptic drug (AED) that has been approved worldwide (in more than 80 countries) for the treatment of various kinds of epilepsy. It is currently being evaluated for its effect in various neurological and psychiatric disorders.

The pharmacokinetics of topiramate are characterised by linear pharmacokinetics over the dose range 100–800mg, low oral clearance (22–36 mL/min), which, in monotherapy, is predominantly through renal excretion (renal clearance 10–20 mL/min), and a long half-life (19–25 hours), which is reduced when coadministered with inducing AEDs such as phenytoin, phenobarbital and carbamazepine. The absolute bioavailability, or oral availability, of topiramate is 81–95% and is not affected by food. Although topiramate is not extensively metabolised when administered in monotherapy (fraction metabolised approximately 20%), its metabolism is induced during polytherapy with carbamazepine and phenytoin, and, consequently, its fraction metabolised increases. During concomitant treatment with topiramate and carbamazepine or phenytoin, the (oral) clearance of topiramate increases 2-fold and its half-life becomes shorter by approximately 50%, which may require topiramate dosage adjustment when phenytoin or carbamazepine therapy is added or discontinued. From a pharmacokinetic standpoint, topiramate is a unique example of a drug that, because of its major renal elimination component, is not subject to drug interaction due to enzyme inhibition, but nevertheless is susceptible to clinically relevant drug interactions due to induction of its metabolism.

Unlike old AEDs such as phenytoin and carbamazepine, topiramate is a mild inducer and, currently, the only interaction observed as a result of induction by topiramate is that with ethinylestradiol. Topiramate only increases the oral clearance of ethinylestradiol in an oral contraceptive at high dosages (>200 mg/day). Because of this dose-dependency, possible interactions between topiramate and oral contraceptives should be assessed according to the topiramate dosage utilised.

This paper provides a critical review of the pharmacokinetic interactions of topiramate with old and new AEDs, an oral contraceptive, and the CNS-active drugs lithium, haloperidol, amitriptyline, risperidone, sumatriptan, propranolol and dihydroergotamine. At a daily dosage of 200mg, topiramate exhibited no or little (with lithium, propranolol and the amitriptyline metabolite nortriptyline) pharmacokinetic interactions with these drugs. The results of many of these drug interaction studies with topiramate have not been published before, and are presented and discussed for the first time in this article.


Carbamazepine Risperidone Valproic Acid Lamotrigine Topiramate 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.



This research work was conducted and funded by Johnson & Johnson Pharmaceutical Research and Development. The work of Professor Meir Bialer was carried out in his capacity as a consultant to Johnson & Johnson Pharmaceutical Research and Development.


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Copyright information

© Adis Data Information BV 2004

Authors and Affiliations

  • Meir Bialer
    • 1
  • Dennis R. Doose
    • 2
  • Bindu Murthy
    • 2
  • Christopher Curtin
    • 2
  • Shean-Sheng Wang
    • 2
  • Roy E. Twyman
    • 2
  • Stefan Schwabe
    • 2
  1. 1.Department of Pharmaceutics, School of Pharmacy and David R. Bloom Center for Pharmacy, Faculty of MedicineThe Hebrew University of JerusalemJerusalemIsrael
  2. 2.Johnson and Johnson Pharmaceutical Research and DevelopmentRaritanUSA

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