Lamotrigine/Phenytoin; Anticonvulsant 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:

Moderate. These medicines may cause some risk when taken together. 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 lamotrigine may change.

What might happen:

Your blood levels of lamotrigine could decrease, reducing the beneficial effects of this medicine.

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), contact your doctor. Your doctor may check the amount of lamotrigine in your blood and may need to adjust the dose of your medicine.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.Lamictal (lamotrigine) US prscribing information. GlaxoSmithKline May, 2018.
  • 2.May TW, Rambeck B, Jurgens U. Serum concentrations of lamotrigine in epileptic patients: the influence of dose and comedication. Ther Drug Monit 1996 Oct;18(5):523-31.
  • 3.Grasela TH, Fiedler-Kelly J, Cox E, Womble GP, Risner ME, Chen C. Population pharmacokinetics of lamotrigine adjunctive therapy in adults with epilepsy. J Clin Pharmacol 1999 Apr;39(4):373-84.
  • 4.Anderson Gail D. Chapter 42: Pharmacokinetics and Drug Interactions. In: Wyllie's Treatment of Epilepsy: Principles and Practice, 5th Ed. 2011.

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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.