Lamotrigine with Phenobarbital Interaction Details
Brand Names Associated with Lamotrigine
- Lamictal®
- Lamictal® CD
- Lamictal® ODT
- Lamictal® XR
- Lamotrigine
Brand Names Associated with Phenobarbital
- Phenobarbital
Medical Content Editor Dr. Brian Staiger, PharmD
Last updated
Nov 08, 2023
Interaction Effect
Reduced lamotrigine efficacy
Interaction Summary
Concomitant use of lamotrigine (metabolized predominantly by glucuronic acid conjugation) with phenobarbital, which is known to induce glucuronidation, has resulted in a 40% decrease in plasma concentrations of lamotrigine. Dose increases of lamotrigine may be necessary to maintain efficacy, especially in patients receiving adjunctive antiepileptics, in patients with bipolar disorder, and in pediatric patients. Dosage of lamotrigine may need to be subsequently decreased when the inducer is discontinued. Lamotrigine dose should be adjusted as clinically indicated.
Severity
Major
Onset
Unspecified
Evidence
Probable
How To Manage Interaction
Concomitant use of lamotrigine (metabolized predominantly by glucuronic acid conjugation) with phenobarbital, which is known to induce glucuronidation, has resulted in a 40% decrease in plasma concentrations of lamotrigine. Dose increases of lamotrigine may be necessary to maintain efficacy, especially in patients receiving adjunctive antiepileptics, in patients with bipolar disorder, and in pediatric patients. Dosage of lamotrigine may need to be subsequently decreased when the inducer is discontinued. Lamotrigine dose should be adjusted as clinically indicated.
Mechanism Of Interaction
Hepatic induction of lamotrigine metabolism by phenobarbital
Literature Reports
A) In drug interactions studies, the addition of phenobarbital or primidone decreased lamotrigine steady-state concentrations by approximately 40% .
B) In 13 patients treated with either carbamazepine or phenobarbital with lamotrigine, the half-life of lamotrigine was 14.1 hours. This group of patients included children over the age of 2 years and young adults with epilepsy that was not controlled with a single agent . The half-life reported in healthy subjects taking lamotrigine alone has been 25.4 hours with repeated dosing .
Lamotrigine Overview
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Lamotrigine extended-release (long-acting) tablets are used with other medications to treat certain types of seizures in patients who have epilepsy. All types of lamotrigine tablets (tablets, orally disintegrating tablets, and chewable tablets) other than the extended-release tablets are used alone or with other medications to treat seizures in people who have epilepsy or Lennox-Gastaut syndrome (a disorder that causes seizures and often causes developmental delays). All types of lamotrigine tablets other than the extended-release tablets are also used to increase the time between episodes of depression, mania (frenzied or abnormally excited mood), and other abnormal moods in patients with bipolar I disorder (manic-depressive disorder; a disease that causes episodes of depression, episodes of mania, and other abnormal moods). Lamotrigine has not been shown to be effective when people experience the actual episodes of depression or mania, so other medications must be used to help people recover from these episodes. Lamotrigine is in a class of medications called anticonvulsants. It works by decreasing abnormal electrical activity in the brain.
Phenobarbital Overview
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Phenobarbital is used to control seizures. Phenobarbital is also used to relieve anxiety. It is also used to prevent withdrawal symptoms in people who are dependent ('addicted'; feel a need to continue taking the medication) on another barbiturate medication and are going to stop taking the medication. Phenobarbital is in a class of medications called barbiturates. It works by slowing activity in the brain.
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Definitions
Severity Categories
Contraindicated
These drugs, generally, should not be used together simultaneously due to the high risk of severe adverse effects. Combining these medications can lead to dangerous health outcomes and should be strictly avoided unless otherwise instructed by your provider.
Major
This interaction could result in very serious and potentially life-threatening consequences. If you are taking this drug combination, it is very important to be under close medical supervision to minimize severe side effects and ensure your safety. It may be necessary to change a medication or dosage to prevent harm.
Moderate
This interaction has the potential to worsen your medical condition or alter the effectiveness of your treatment. It's important that you are monitored closely and you potentially may need to make adjustments in your treatment plan or drug dosage to maintain optimal health.
Minor
While this interaction is unlikely to cause significant problems, it could intensify side effects or reduce the effectiveness of one or both medications. Monitoring for changes in symptoms and your condition is recommended, and adjustments may be made if needed to manage any increased or more pronounced side effects.
Onset
Rapid: Onset of drug interaction typically occurs within 24 hours of co-administration.
Delayed: Onset of drug interaction typically occurs more than 24 hours after co-administration.
Evidence
Level of documentation of the interaction.
Established: The interaction is documented and substantiated in peer-reviewed medical literature.
Theoretical: This interaction is not fully supported by current medical evidence or well-documented sources, but it is based on known drug mechanisms, drug effects, and other relevant information.
How To Manage The Interaction
Provides a detailed discussion on how patients and clinicians can approach the identified drug interaction as well as offers guidance on what to expect and strategies to potentially mitigate the effects of the interaction. This may include recommendations on adjusting medication dosages, altering the timing of drug administration, or closely monitoring for specific symptoms.
It's important to note that all medical situations are unique, and management approaches should be tailored to individual circumstances. Patients should always consult their healthcare provider for personalized advice and guidance on managing drug interactions effectively.
Mechanism Of Interaction
The theorized or clinically determined reason (i.e., mechanism) why the drug-drug interaction occurs.
Disclaimer: The information provided on this page is for informational purposes only and should not be considered medical advice. Always consult with a qualified healthcare professional regarding your specific circumstances and medical conditions.
Where Does Our Information Come From?
Information for our drug interactions is compiled from several drug compendia, including:
The prescribing information for each drug, as published on DailyMED, is also used.
Individual drug-drug interaction detail pages contain references specific to that interaction. You can click on the reference number within brackets '[]' to see what reference was utilized.
The information posted is fact-checked by HelloPharmacist clinicians and reviewed quarterly.