Herb & supplement monograph

Phenibut Drug Interactions, Uses, Effectiveness, Safety & More

Medically reviewed by Dr. Brian Staiger, PharmD, BCPS ·Updated July 2026

What is this page for?

First and foremost: how Phenibut interacts with medications. The heart of this page is the interaction list — every drug Phenibut is known to interact with, and how serious each one is.

But these pages have grown well beyond that into a full monograph — what Phenibut is, what people use it for and how strong the evidence is, its safety and side effects, and answers to the questions we’re asked most — written and reviewed by the clinical staff at HelloPharmacist. It’s educational information from our licensed clinical databases, not medical advice, and we don’t sell or endorse products. Our editorial policy

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Phenibut Drug Interactions: The Bottom Line

From the HelloPharmacist Editorial Team · Updated July 2026

Based on the available evidence, Phenibut drug interactions carry a moderate risk of causing real problems for most people, mainly with medications that slow the brain and cause drowsiness. Every listed interaction is rated moderate, none major or minor, though the documentation comes mostly from case reports and theory rather than controlled human studies.

Interactions deserving the most attention

The combinations that deserve the most care involve CNS depressants, meaning medicines that cause sedation, because Phenibut has been linked in case reports to deep sedation and slowed breathing, especially at high doses, and adding another sedating drug could make that worse. Pregabalin (Lyrica) also stands out, since Phenibut is chemically similar to it and both act on the same calming receptors in the brain, so taking them together may pile on side effects like drowsiness.

What the rest of the list means

The long list of interacting medications largely reflects how many drugs have sedating effects, not hundreds of separate proven problems. Most of these concerns are theoretical or drawn from a handful of case reports, and none have been confirmed in well-controlled human studies. Still, the pattern points consistently in one direction: added sleepiness and slowed breathing are the effects to watch for.

Check your medications against Phenibut

Based on HelloPharmacist’s Phenibut interaction data and reviewed under our editorial standards.

Interaction report

Drugs that interact with Phenibut

248 medications have a known interaction with Phenibut, graded by severity. Select any drug for the full evidence-based detail.

Don’t want to scroll the list? Just ask.

Tell us the medications you take and we’ll check each one against Phenibut using our pharmacist-reviewed interaction data.

AI summaries are generated from our Phenibut interaction data for education only — always confirm with your pharmacist. How we use AI

2,830 drugs

Read The List Like a Pharmacist

What Severity, Likelihood & Evidence Mean

Severity — How Serious It Can Be

Major. Clinically significant; generally best avoided, or used only under direct professional supervision.
Moderate. May need monitoring, a dose adjustment, or separating the times you take each one.
Minor. Generally not clinically significant, but still worth noting and mentioning to your pharmacist.
No known interaction. Checked against our sources with nothing documented — not the same as proven safety.

Likelihood — How Well It’s Documented

Likely. Well-controlled human studies have demonstrated the likely existence of this interaction
Probable. Interaction 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.
Possible. 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
Unlikely. Interaction has been demonstrated in animal or in lab research but has been shown not to occur in humans.

Where This Data Comes From

Interaction records are evidence-graded and sourced from the Natural Medicines database (TRC Healthcare), the same reference used by pharmacists and hospitals.
Each drug listed above links to the full report for that exact Phenibut combination — clinical detail, likelihood, evidence level, and citations.
Content is reviewed by licensed HelloPharmacist pharmacists — see our data sources and editorial standards.

The big picture

The kinds of drugs Phenibut affects

Every type of medication (drug category) Phenibut is known to interact with. Open any category for the detail — or search your exact drug in the checker above.

All 2 drug categories Phenibut interacts with

Cns DepressantsPregabalin (lyrica)

Cns Depressants

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.

Likelihood Possible Evidence D

Pregabalin (Lyrica)

Theoretically, phenibut might increase the risk for additive adverse effects, including sedation, when taken with pregabalin.
Phenibut is structurally related to pregabalin, and both chemicals act at GABA receptors in the brain. In a case report, a patient who had experienced tolerance to the effects of pregabalin for treatment of chronic neuropathic pain experienced a reduction in tolerance when phenibut was taken concurrently.

Likelihood Possible Evidence D

Monograph

Phenibut: Uses, Safety & Side Effects

Medically reviewed by Dr. Brian Staiger, PharmD, BCPS · Reviewed July 2026 ·

The bottom line

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.

Part used: Synthetic compound (not a plant part)
Common forms: Powder, capsules, tablets

People commonly use it for

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

Popular and traditional uses — not proof it works. See “Uses & effectiveness” below for the evidence.

Safety at a glance

OverallBest avoided

Phenibut carries a high risk of dependence, dangerous withdrawal, and overdose, and is not approved as a supplement or drug in the U.S.

PregnancyInsufficient reliable information

Insufficient reliable information available; avoid using. A case of phenibut withdrawal in the neonate is reported after use of high doses (i.e. 5-12...

Read the full pregnancy detail

BreastfeedingInsufficient reliable information

Insufficient reliable information available; avoid using.

Read the full breastfeeding detail

Pregnancy & breastfeeding ratings are from Natural Medicines (Therapeutic Research Center). Safety guidance is general; always confirm with your pharmacist or doctor for your situation.

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Overview

Phenibut is a man-made (synthetic) chemical, not an herb or plant. It was first developed in the Soviet Union and has been used there as a prescription medicine for anxiety, tension, and sleep problems. In some countries it is still sold as a pharmaceutical drug.

Phenibut is a close chemical relative of a brain chemical called GABA (gamma-aminobutyric acid), which helps calm the nervous system. It is structurally similar to certain prescription medicines such as gabapentin, pregabalin, and baclofen.

In the United States and several other countries, phenibut is not approved as a medicine or as a dietary supplement. Despite this, it is sometimes sold online as a powder or capsule and marketed for anxiety, stress, sleep, and even "focus" or workouts. Because it is unregulated when sold this way, product quality and dosing can be unreliable.

How it works

Phenibut is built from the calming brain chemical GABA, with an extra part added to its structure that lets it cross from the bloodstream into the brain more easily. Once in the brain, it is thought to act on GABA receptors, which slow down nerve activity and produce a calming, sedating effect.

At higher amounts, phenibut may also affect other brain systems, including certain calcium channels (similar to how gabapentin and pregabalin work). These ideas are based largely on laboratory and animal research, so the exact way it works in people is not fully understood.

Because it slows down the central nervous system, phenibut can make you feel relaxed or sleepy—but it can also build tolerance quickly, meaning the body needs more to get the same effect over time.

Effectiveness

Does Phenibut work?

Here’s what the research actually shows for each use — graded by Natural Medicines and reviewed by Dr. Brian Staiger, PharmD.

Evidence overview · 9 uses evaluated

9 Insufficient evidence

How to read these evidence grades

Natural Medicines’ 7-point scale. We show each rating’s label word-for-word.

1EffectiveStrong, consistent evidence it works.

2Likely EffectiveGood evidence, though not yet conclusive.

3Possibly EffectiveSome evidence suggests a benefit.

4Possibly IneffectiveSome evidence it may not help.

5Likely IneffectiveFairly strong evidence it doesn’t help.

6IneffectiveStrong evidence it doesn’t work.

7Insufficient Reliable Evidence to RateToo little research to say either way.

For Phenibut, current evidence isn’t strong enough to rate any specific use. The conditions it has been studied for are listed below.

Also studied for 9 conditions — evidence insufficient to rate

Insufficient Reliable Evidence To Rate Alcohol use disorder