Drug & supplement interaction

Phenibut + Valbenazine Tosylate

Valbenazine Tosylate brand name: Ingrezza.

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

Phenibut has a moderate interaction with Valbenazine Tosylate. 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 Valbenazine Tosylate

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

Moderate

CNS DEPRESSANTS

Why this applies to Valbenazine Tosylate

Valbenazine Tosylate 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 Ingrezza (valbenazine) can slow down your brain and nervous system. Valbenazine often causes drowsiness on its own, and phenibut is a powerful sedative. Put them together and those calming effects can stack up, leaving you extra sleepy, foggy, or unsteady. In higher amounts, phenibut has been linked to slowed breathing, so the worry is that combining the two could make sedation deeper than either one alone.

I'll be honest, this concern is based on how these substances work rather than firm studies in people, so think of it as a reasonable caution. I also want to flag that we don't recommend phenibut at all, since it can cause dependence and rough withdrawal. Please loop in your doctor or pharmacist before mixing anything with your valbenazine.

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 Valbenazine Tosylate 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. Valbenazine Tosylate)
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.

Everything else you take

See Every Supplement That Interacts With Valbenazine Tosylate

This page covers Phenibut only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Valbenazine Tosylate page lists 216 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), American Hellebore (major), Arsenic (major) and Beer (major).

By severity: 14 major · 164 moderate · 38 minor.

From our pharmacist’s overview on the Valbenazine Tosylate page

“The list for valbenazine (Ingrezza), the medicine for tardive dyskinesia, warrants genuine care, since 14 of its 216 supplement and herbal interactions are rated major. Most of those majors either pile extra sedation onto a drug that can already make people drowsy, alcohol being the everyday example, or shift how much valbenazine reach…”

Reviewed by 2 · Jul 18, 2026

Open the Valbenazine Tosylate 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 Valbenazine Tosylate 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 Valbenazine Tosylate 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

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

29 days ago today
Medication Valbenazine Tosylate
Steady interest

#1,558 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 Valbenazine

What Is Valbenazine Used For?

Brand name: Ingrezza

Valbenazine — sold as Ingrezza and INGREZZA Sprinkle — is approved for two conditions in adults. The first is tardive dyskinesia, a movement disorder that causes uncontrolled, repetitive facial or body movements, often brought on by long-term use of certain psychiatric medications. The second is chorea associated with Huntington's disease, which refers to the involuntary, dance-like jerking movements that are a hallmark of that condition.

Both Ingrezza and INGREZZA Sprinkle are approved for both of these uses.

See full Valbenazine 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 Valbenazine Tosylate, 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 Valbenazine Tosylate supplement interactions › Every supplement checked against Valbenazine Tosylate, ranked by severity Valbenazine 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 Valbenazine Tosylate Together: Common Questions

Can you take Phenibut with Valbenazine Tosylate?
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 Valbenazine Tosylate 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 Valbenazine Tosylate 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.