Drug & supplement interaction

Phenibut + Carbamazepine

Carbamazepine brand names: Tegretol, Tegretol XR, Equetro, Carbatrol, Carnexiv.

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

Phenibut has a moderate interaction with Carbamazepine. Theoretically, phenibut might increase the risk of sedation and respiratory depression when taken with CNS depressants.

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

Phenibut and Carbamazepine

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

Moderate

CNS DEPRESSANTS

Why this applies to Carbamazepine

Carbamazepine falls under CNS DEPRESSANTS — the group Phenibut interacts with.

Theoretically, phenibut might increase the risk of sedation and respiratory depression when taken with CNS depressants.
Phenibut has been associated with sedation and respiratory depression in several case reports, especially when taken at high doses.
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 simple version: both phenibut and carbamazepine (Tegretol) calm down the brain and nervous system. When you stack two sedating substances together, those calming effects can add up. With carbamazepine, that could mean extra drowsiness, dizziness, unsteadiness on your feet, or trouble concentrating. At higher phenibut doses, the bigger worry is slowed or shallow breathing, since phenibut has been linked to that in case reports.

I want to be honest with you, this concern is theoretical, based on how these substances work rather than solid studies of the two together. Still, phenibut isn't an approved supplement and carries real risks of dependence and withdrawal. Please talk with your doctor or pharmacist before combining them, and ask about safer, proven options for anxiety or sleep.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Downes MA, Berling IL, Mostafa A, Grice J, Roberts MS, Isbister GK. Acute behavioural disturbance associated with phenibut purchased via an internet supplier. Clin Toxicol (Phila). 2015;53(7):636-8. PubMed
  2. O'Connell CW, Schneir AB, Hwang JQ, Cantrell FL. Phenibut, the appearance of another potentially dangerous product in the United States. Am J Med. 2014 Aug;127(8):e3-4. PubMed
  3. Sankary S, Canino P, Jackson J. Phenibut overdose. AM J Emerg Med. 2017 Mar;35(3):516.e1-516.e2.
  4. Graves JM, Dilley J, Kubsad S, Liebelt E. Notes from the field: phenibut exposures reported to poison centers - United States, 2009-2019. MMWR Morb Mortal Wkly Rep 2020;69(35):1227-8. 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

Phenibut Also Interacts With Other Medications

Phenibut has 247 moderate known drug interactions in our database — the Carbamazepine one above is one of them. If you take anything else, check it against the full list below.

Moderate 247 No known interaction 2,583 (incl. Carbamazepine)
Taking anything else?

Check Another of Your Medications Against Phenibut

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

From our Q&A

Questions About Phenibut or Carbamazepine

These are real questions from readers, answered by the pharmacists at HelloPharmacist — written by a person, not generated from a database. Each one covers Phenibut or Carbamazepine, 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 Carbamazepine

This page covers Phenibut only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Carbamazepine page lists 284 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), Asarabacca (major), Beer (major) and Gamma-hydroxybutyrate (ghb) (major).

By severity: 12 major · 235 moderate · 37 minor.

From our pharmacist’s overview on the Carbamazepine page

“Carbamazepine (Tegretol, Carbatrol, Equetro) only controls seizures and mood episodes when its blood level stays inside a tight window, and 284 supplement and herbal ingredients on file can disturb that balance, 12 of them rated major. Grapefruit can push carbamazepine levels up, St.”

Reviewed by 2 · Jul 18, 2026

Open the Carbamazepine interaction page

One more smart check

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

We hold 41 real supplement products containing Phenibut, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Phenibut. Your product may carry other ingredients that interact with Carbamazepine too, on top of Phenibut — 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 Phenibut and Carbamazepine 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 Phenibut
Top half

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

29 days ago today
Medication Carbamazepine
Top 25%

#389 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 Phenibut

What is Phenibut?

Phenibut
  • Anxiety and stress
  • Insomnia and sleep problems
  • Stress relief
  • Mood and focus
  • Reducing alcohol withdrawal symptoms (unproven)

Phenibut is a synthetic, lab-made central nervous system depressant—not a natural herb—that some people use for anxiety and sleep, but it carries a serious risk of tolerance, dependence, and dangerous withdrawal. It is not an approved medication or dietary supplement in the United States, and we do not recommend its use. Talk to a doctor or pharmacist about safer, proven options for anxiety or sleep.

Read the full Phenibut monograph & all interactions
Medication

About Carbamazepine

What Is Carbamazepine Used For?

Brand names: Tegretol, Tegretol XR, Equetro, Carbatrol, Carnexiv

Carbamazepine is used to treat certain types of seizures — including partial seizures, generalized tonic-clonic (grand mal) seizures, and mixed seizure patterns. It works best for those specific seizure types; it does not appear to control absence (petit mal) seizures.

It is also prescribed to relieve the intense facial pain of trigeminal neuralgia — a nerve condition that causes sudden, severe pain along the face. It is not a general painkiller and shouldn't be used for ordinary aches and pains.

See full Carbamazepine drug information
Keep checking

Other Drugs & Phenibut

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

0Major
247Moderate
0Minor
2,582No known interaction
247 Moderate 2,582 No interaction
Moderate

247 interactions

Showing 60 of 247 moderate interactions — see all 247 on the Phenibut page.

No interaction 2,582 drugs checked — show the list

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

Showing the 60 most looked-up of 2,582 medications checked with no known interaction — see the full Phenibut list.

See the full Phenibut interactions page
See every supplement checked against Carbamazepine, 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
Phenibut monograph › Uses, safety, and every drug interaction in one place Carbamazepine supplement interactions › Every supplement checked against Carbamazepine, ranked by severity Carbamazepine drug information › The full plain-English guide to this medication 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 Phenibut and Carbamazepine Together: Common Questions

Can you take Phenibut with Carbamazepine?
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 Phenibut and Carbamazepine 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 Carbamazepine and Phenibut?

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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.