Drug & supplement interaction

Glutamine + Phenobarbital, Phenytoin

Phenobarbital, Phenytoin brand name: Dilantin with PB.

Moderate Interaction
Medically reviewed by · Updated September 2026
The bottom line Moderate

Glutamine has a moderate interaction with Phenobarbital, Phenytoin. Theoretically, glutamine might antagonize the effects of anticonvulsant medications.

Read the full interaction report
SeverityModerate
LikelihoodPossible
EvidenceD
What do Severity, Likelihood & Evidence mean?
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Interaction report

Glutamine and Phenobarbital, Phenytoin

Here is the interaction we found between these two, with the evidence behind it.

Moderate

ANTICONVULSANTS

Why this applies to Phenobarbital, Phenytoin

Phenobarbital, Phenytoin falls under ANTICONVULSANTS — the group Glutamine interacts with.

Theoretically, glutamine might antagonize the effects of anticonvulsant medications.
Glutamine is metabolized to the excitatory neurotransmitter glutamate. Glutamate might have antagonistic effects with anticonvulsant drugs. However, this interaction has not yet been reported in humans.
Severity Moderate Likelihood Possible Evidence D

Interaction has been documented in animal or in lab research, or the interaction has been documented in humans but is limited to case reports or conflicting clinical research exists.

Dr. Brian Staiger, PharmD, BCPS
Dr. Brian Staiger explains PharmD, Clinical Pharmacist

Here's the thinking behind pairing glutamine with a combo like phenytoin and phenobarbital. In your body, glutamine can be converted into glutamate, which is one of the brain's main excitatory signals. Seizure medicines like these work partly by calming down that kind of activity, so on paper a lot of extra glutamate could push in the opposite direction and slightly blunt seizure control.

The honest part: this is a theoretical concern only. It comes from how these chemicals behave in the lab, and it has not actually been reported in people taking glutamine. Everyday food protein already contains glutamine without causing trouble. Still, since uncontrolled seizures are serious, I'd run any concentrated glutamine supplement past your doctor or pharmacist first, especially if your seizures are well controlled now.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Meldrum BS. Glutamate as a neurotransmitter in the brain: review of physiology and pathology. J Nutr 2000;130:1007S-15S.. PubMed
  2. Garlick PJ. Assessment of the safety of glutamine and other amino acids. J Nutr 2001;131:2556S-61S.. PubMed
  3. Chapman AG. Glutamate and epilepsy. J Nutr 2000;130:1043S-5S.. PubMed

What These Ratings Mean

Every interaction above is graded three ways — here’s the key to each label.

Severity how clinically significant the interaction is
Major

Clinically significant. Avoid the combination, or use only under close professional supervision.

Moderate

Usually worth avoiding or managing — may need monitoring, a dose change, or timing apart.

Minor

Generally not serious. Be aware of it and mention it to your pharmacist.

Likelihood how strong the evidence is that the interaction actually happens in people
  • LikelyWell-controlled human studies have demonstrated the likely existence of this interaction.
  • ProbableInteraction has not been documented in well-controlled studies, however, the interaction has been demonstrated in some small human studies or in controlled animal studies in conjunction with multiple case reports.
  • PossibleInteraction has been documented in animal or in lab research, or the interaction has been documented in humans but is limited to case reports or conflicting clinical research exists.
  • UnlikelyInteraction has been demonstrated in animal or in lab research but has been shown not to occur in humans.
Evidence the quality of the studies behind the rating (graded A–D)
  • AHigh-quality meta-analysis (quantitative systematic review).
  • BCase-control study.
  • CConsensus.
  • DAnecdotal evidence.

These ratings are for information only. Never start, stop, or otherwise change your therapy before speaking with your provider.

Keep it in perspective

Glutamine Also Interacts With Other Medications

Glutamine has 49 moderate known drug interactions in our database — the Phenobarbital, Phenytoin one above is one of them. If you take anything else, check it against the full list below.

Moderate 49 No known interaction 2,781 (incl. Phenobarbital, Phenytoin)
Taking anything else?

Check Another of Your Medications Against Glutamine

Covers the 2,830 medications we’ve checked against Glutamine. Pick one to open its full report.

From our Q&A

Questions About Glutamine or Phenobarbital, Phenytoin

These are real questions from readers, answered by the pharmacists at HelloPharmacist — written by a person, not generated from a database. Each one covers Glutamine or Phenobarbital, Phenytoin, not necessarily both, but if one is close to what you were about to ask it will usually go further than a database entry can:

Not quite your question? Ask our pharmacists directly — it is free, there is no account required, and answers usually come back within 24 hours.

Everything else you take

See Every Supplement That Interacts With Phenobarbital, Phenytoin

This page covers Glutamine only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Phenobarbital, Phenytoin page lists 229 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: 1,4-butanediol (major), Activated Charcoal (major), Beer (major), Gamma-hydroxybutyrate (ghb) (major) and Kava (major).

By severity: 9 major · 192 moderate · 28 minor.

From our pharmacist’s overview on the Phenobarbital, Phenytoin page

“If your seizure medicine is the phenobarbital and phenytoin combination (Dilantin with PB), read this list carefully before you add any supplement. Nine of the 229 entries rate major, and most of the risk runs through two channels.”

Reviewed by 2 · Jul 18, 2026

Open the Phenobarbital, Phenytoin interaction page

One more smart check

Taking Glutamine as Part of a Dietary Supplement Product? Check It for Interactions

We hold 5,253 real supplement products containing Glutamine, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Glutamine. Your product may carry other ingredients that interact with Phenobarbital, Phenytoin too, on top of Glutamine — and those would not show on this page. Find your product and we’ll check every ingredient on its label:

How much people look this up

Where Glutamine and Phenobarbital, Phenytoin Sit Against Everything Else

Out of every supplement and medication people look up on HelloPharmacist, here is where these two land this week — and which way each has been moving.

Supplement Glutamine
Top 5%

#43 of 1,452 supplements looked up here in the last 7 days

29 days ago today
Medication Phenobarbital, Phenytoin
Steady interest

#2,211 of 2,830 medications looked up here in the last 7 days

29 days ago today

Position among everything looked up on this site, not a measure of how commonly either one is used or how important it is. A supplement can climb this list because of a news story. It counts every request to the page, automated ones included, and nothing here identifies anyone.

Supplement

About Glutamine

What is Glutamine?

  • Muscle recovery and sports performance
  • Gut health and 'leaky gut'
  • Recovery from severe illness or injury
  • Immune support
  • Side effects of cancer treatment (mucositis)
  • Sickle cell disease (prescription form)

Glutamine is the most abundant amino acid in the body and is usually made in your muscles. A prescription form is FDA-approved to help reduce sickle cell disease complications, but for most popular uses such as muscle building, gut health, and immunity the evidence is limited or mixed. It is generally well tolerated in healthy people, but anyone with serious liver or kidney problems should check with a doctor first.

Read the full Glutamine monograph & all interactions
Keep checking

Other Drugs & Glutamine

Browse every other medication we’ve checked against Glutamine — both the ones with a known interaction and the ones without. Select any drug for the full detail.

0Major
49Moderate
0Minor
2,780No known interaction
49 Moderate 2,780 No interaction
Moderate

49 interactions

No interaction 2,780 drugs checked — show the list

We also checked Glutamine against these medications and found no known interaction in our sources. Open any page to confirm.

Showing the 60 most looked-up of 2,780 medications checked with no known interaction — see the full Glutamine list.

See the full Glutamine interactions page
See every supplement checked against Phenobarbital, Phenytoin, ranked by severity
Sources

Sources & How We Checked

Interaction details are evidence-graded and sourced from the Natural Medicines database. The medication overview comes from MedlinePlus.

Content is written and reviewed by licensed HelloPharmacist pharmacists. See our data sources and editorial standards for how this information is built and checked.

Parts of this content are provided by the Therapeutic Research Center, LLC.

DISCLAIMER: Currently this does not check for drug-drug interactions. This is not an all-inclusive comprehensive list of potential interactions and is for informational purposes only. Not all interactions are known or well-reported in the scientific literature, and new interactions are continually being reported. Input is needed from a qualified healthcare provider including a pharmacist before starting any therapy. Application of clinical judgment is necessary.

© 2021 Therapeutic Research Center, LLC

Keep exploring
Glutamine monograph › Uses, safety, and every drug interaction in one place Phenobarbital, Phenytoin supplement interactions › Every supplement checked against Phenobarbital, Phenytoin, ranked by severity Supplement interaction checker › Check any supplement or product against your medications Browse medications A–Z › Every drug we've checked against herbs & supplements Ask a pharmacist › Free, personal answer from our licensed team
Pharmacist Counseling Corner

Taking Glutamine and Phenobarbital, Phenytoin Together: Common Questions

Can you take Glutamine with Phenobarbital, Phenytoin?
There is a moderate interaction, so it may be acceptable with monitoring or timing changes — but check with your pharmacist first. Read the full details on this page and confirm with your pharmacist before combining them.
How serious is the Glutamine and Phenobarbital, Phenytoin interaction?
We rate it Moderate. This combination may require monitoring, a dose adjustment, or separating the times you take each one. Consult your pharmacist before using them together.

Written and reviewed by the HelloPharmacist editorial staff. Our editorial policy

Still Have a Question About Phenobarbital, Phenytoin and Glutamine?

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This information is for education only and is not a substitute for professional medical advice. Always check with your pharmacist or doctor before starting, stopping, or combining supplements and medications.