Selected Anticonvulsants/Selected Barbiturates Interactions

This information is generalized and not intended as specific medical advice. Consult your healthcare professional before taking or discontinuing any drug or commencing any course of treatment.

Medical warning:

Serious. These medicines may interact and cause very harmful effects. Contact your healthcare professional (e.g. doctor or pharmacist) for more information.

How the interaction occurs:

When these two medicines are taken together, the way your body processes each medicine may change.

What might happen:

Your blood levels of medicine could decrease, reducing the beneficial effects of this medicine, or increase and cause toxic effects.

What you should do about this interaction:

Let your healthcare professional (e.g. doctor or pharmacist) know that you are taking these medicines together. If you notice decreased effectiveness of your medicine (e.g. increase in seizures, migraine headaches, or unstable mood) or if you experience symptoms of high blood levels such as drowsiness, headache, dizziness, slowed/difficult breathing, confusion, or difficulty with coordination, contact your doctor. Your doctor may check medicine blood levels and may need to adjust the dose of one or both medicines.Your healthcare professionals (e.g. doctor or pharmacist) may already be aware of this interaction and may be monitoring you for it. Do not start, stop, or change the dosage of any medicine before checking with them first.

  • 1.Depakote (divalproex sodium) US prescribing information. AbbVie Inc. February, 2023.
  • 2.Patel IH, Levy RH, Cutler RE. Phenobarbital--valproic acid interaction. Clin Pharmacol Ther 1980 Apr;27(4):515-21.
  • 3.Bruni J, Wilder BJ, Perchalski RJ, Hammond EJ, Villarreal HJ. Valproic acid and plasma levels of phenobarbital. Neurology 1980 Jan;30(1):94-7.
  • 4.Windorfer A Jr, Sauer W, Gadeke R. Elevation of diphenylhydantoin and primidone serum concentration by addition of dipropylacetate, a new anticonvulsant drug. Acta Paediatr Scand 1975 Sep;64(5):771-2.
  • 5.Wilder BJ, Willmore LJ, Bruni J, Villarreal HJ. Valproic acid: interaction with other anticonvulsant drugs. Neurology 1978 Sep;28(9 Pt 1):892-6.
  • 6.Reunanen MI, Luoma P, Myllyla VV, Hokkanen E. Low serum valproic acid concentrations in epileptic patients on combination therapy. Curr Ther Res 1980 Sep;28(3):456-62.
  • 7.Henriksen O, Johannessen SI. Clinical and pharmacokinetic observations on sodium valproate - a 5- year follow-up study in 100 children with epilepsy. Acta Neurol Scand 1982 May;65(5):504-23.
  • 8.Johnson GJ, Kilpatrick CJ, Bury RW, Fullinfaw RO, Moulds RF. Unbound phenytoin plasma concentrations in patients comedicated with sodium valproate--the predictive value of plasma albumin concentration. Br J Clin Pharmacol 1989 Jun;27(6):843-9.
  • 9.Trileptal (oxcarbazepine) US prescribing information. Novartis Pharmaceuticals Corporation November, 2017.
  • 10.Oxtellar XR (oxcarbazepine) extended-release US prescribing information. Supernus, Inc. December, 2018.
  • 11.Felbatrol (felbamate) US prescribing information. MedPoint Pharmaceuticals Inc. August 27, 2012.
  • 12.Reidenberg P, Glue P, Banfield CR, Colucci RD, Meehan JW, Radwanski E, Mojavarian P, Lin CC, Nezamis J, Guillaume M, et al. Effects of felbamate on the pharmacokinetics of phenobarbital. Clin Pharmacol Ther 1995 Sep; 58(3):279-87.
  • 13.Kelley MT, Walson PD, Cox S, Dusci LJ. Population pharmacokinetics of felbamate in children. Ther Drug Monit 1997 Feb;19(1):29-36.
  • 14.Gidal BE, Zupanc ML. Potential pharmacokinetic interaction between felbamate and phenobarbital. Ann Pharmacother 1994 Apr;28(4):455-8.

Selected from data included with permission and copyrighted by First Databank, Inc. This copyrighted material has been downloaded from a licensed data provider and is not for distribution, except as may be authorized by the applicable terms of use.

CONDITIONS OF USE: The information in this database is intended to supplement, not substitute for, the expertise and judgment of healthcare professionals. The information is not intended to cover all possible uses, directions, precautions, drug interactions or adverse effects, nor should it be construed to indicate that use of a particular drug is safe, appropriate or effective for you or anyone else. A healthcare professional should be consulted before taking any drug, changing any diet or commencing or discontinuing any course of treatment.