Issac Thorne

Last Updated January 9, 2022

Curious about phenibut half-life? You’re in the right spot.

Phenibut is one of the most promising nootropics under study right now. Research is mounting regarding its role in enhancing cognition, improving mood, reducing anxiety, enhancing sleep, and improving sociability.

Nootropic researchers like you are the key to learning more about this exciting, yet understudied compound.

But maybe you’re wondering about how it works—and how long it takes for the human body to clear it.

When does phenibut peak? How long does phenibut stay in the human system? What should research subjects expect? How long does phenibut last?

We’ll address all those questions here.

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What Is Phenibut?

Before discussing how long it takes for phenibut to break down in the body, let’s go over what it is.

Phenibut is a central nervous system tranquilizer developed in the 1960s in the former Soviet Union [1]. It was originally produced as a treatment for insomnia and anxiety, and it is still used as a prescription medication in some countries for those conditions [1]. It is a psychotropic drug, which means that it can temporarily alter a person’s perception, mood, behavior, and consciousness.

Phenibut is a synthetic form of GABA (gamma-aminobutyric acid), which is an amino acid and one of the most important neurotransmitters that we produce naturally in our bodies. GABA is responsible for reducing nerve excitability—it creates calm and relaxation. GABA regulates and reduces brain agitation by inhibiting excessive neuron firing.

Phenibut effects

Characterized as a GABA analog, phenibut activates GABA receptors, primarily the slower-acting GABAB receptors and and secondarily the faster-acting GABAA receptors, at high levels. Phenibut thus has a calming effect on the brain and also seems to upregulate dopamine [1].

Due to its effectiveness, phenibut is used as a prescription tranquilizer in several countries, including Russia, Ukraine, and Belarus. Where it’s approved as a prescription drug, phenibut is used to treat conditions like anxiety, depression, alcoholism, nausea, and even stuttering [1]. In studies on neurotic and psychotic patients, it has been found to “activate intellectual functions, improve physical strength, motivate activity and to reduce asthenia and tiredness” [1].


Phenibut Side Effects and Safety

Phenibut appears to have some unquestionably positive effects, but what about its safety profile? What are the potential side effects?

First, phenibut is generally well-tolerated by healthy adults [1]. It has been used as a medication for almost 40 years in several countries. But like any drug, it is also capable of causing side effects.

Namely, some users report gastrointestinal side effects. These include [4]:

  • Vomiting
  • Nausea
  • Diarrhea

Although rare, other users report psychological symptoms and symptoms linked to the central nervous system. These include [4]:

  • Insomnia
  • Depression
  • Confusion

To avoid potential side effects, limit how much your test subjects take. Start their phenibut dosing small, and build up after you know how their bodies react to it.

Also, to avoid interactions, ensure your test subjects don’t mix it with:

  • Alcohol
  • Benzodiazepines
  • Anticonvulsant medications
  • Opioids
  • Anti-psychotics
  • Sedatives

Note that, in the United States, there has been at least one death reported from the use of phenibut alone, though the circumstances surrounding that death have not been reported to the public [5].

Prolonged use of high doses of phenibut may trigger dependence and addiction—a compulsion to take a drug with loss of control over drug intake [2, 3]. Phenibut also has some interaction effects, which means your test subjects need to be careful that they do not take it with certain substances.


Phenibut Half-Life

Let’s get to the meat and potatoes of this guide.

You want to know what the half-life of phenibut is and how long will its effects last. Let's dig in…

What is the phenibut half-life?

A substance's half-life is the average time it takes for the concentration of a substance to be reduced by half in the body.

The phenibut plasma half-life is about 5.3 hours, according to clinical studies conducted in Russia [6]. That means that it takes about 5.3 hours for a dose of 500 mg to be reduced to 250 mg. After another 5.3 hours, it’ll be reduced to 125 mg. Then another 5.3 hours to get to about 62 mg. And so on.

Keep in mind that there are a number of factors that affect the half-life of phenibut, so it could be a bit less or a bit more for any given human subject. These factors include things like:

  • Age
  • Metabolism
  • Weight

What is the phenibut high and when does it kick in?

A phenibut study participant can expect to feel the effects of phenibut one to two hours after ingestion.

This is important to clarify with your test subjects: they may not realize that it may take awhile to feel the effects of phenibut, so they might think they need a higher dose. Let your test subjects know that they should stick it out and wait for up to two hours before drawing any conclusions.

Once the effects kick in, test subjects may feel a heightened cognition, a sense of well-being, and an increase in sociability.

These effects have been found in some research studies. One small study in patients with anxiety-phobic disorders found phenibut improved scores on attention tasks, memory tasks, and an emotional intelligence test [7]. In a small study on rabbits, phenibut was found to improve learning in a particular context [8]. In studies on rats, phenibut was found to have nootropic and neuroprotective effects [9].

When is the phenibut peak and how long does it last?

One of the most common questions is, “How long does the phenibut peak last?”

It appears that the “phenibut high” usually lasts for about 4 to 6 hours once drug kicks in [6].

So, if your test subjects consume phenibut at 7:00 pm, it’s reasonable to expect that they will start feeling it between 8:00 and 9:00 pm, and that peak effects will last until about 2:00 am.

While the “high” feeling decreases at about the 6 hour mark, test subjects may experience “afterglow” effects from phenibut for many hours after [6]. Some have even reported feeling these effects up to 24 hours after taking a dose [6].

How long does phenibut stay in the system?

The main factor influencing the length of time that phenibut remains in the body is your test subjects’ dosage, as well as the tolerance level of each individual [7].

Factors like age, metabolism, and weight can all influence the time it will take for phenibut to completely leave the body. For example, older test subjects who consume higher doses of phenibut tend to excrete it more slowly than people who are younger.

Are the effects of phenibut intense over a long time-frame?

Although the effects of phenibut are long-lasting, with phenibut your test subjects should remain perfectly conscious and able to think clearly. The phenibut high is comparable to that of other drugs.

Of course, as with any other medication or drug, the greater the dosage, the more intense the effects and the longer they last.

Again, depending on factors like your test subjects’ age, size, and metabolism, the effects can be more or less intense. That’s why you may consider establishing a research protocol that starts off at a relatively low phenibut dosage. This will allow you to see how phenibut affects your test subjects and help you judge how to dose phenibut for research purposes going forward.

Where To Buy Phenibut Online | 2022 Guide

If you’re a qualified researcher, you can legally buy phenibut online, unless you are in Hungary, Australia, Italy, France, or Lithuania, where it has been banned.

In the United States, phenibut is classified as a “New Drug” under the Federal Food, Drug, and Cosmetic Act (FD&C Act) in the US. That means it has not been investigated (or approved) for use as a medicine or otherwise.

Although phenibut is not approved for medical use in North America or Europe, it is widely used for nootropic research and it’s available online.

Tip: to avoid falling for scams, only buy phenibut from a legitimate vendor.

Our go-to vendor is They’ve provided us with excellent service and their research-grade phenibut is subject to a strict quality control process to ensure that it’s free adulterants, excipients, and flow agents. With consumer-friendly shipping and return policies, order from this vendor with confidence!

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Half-Life of Phenibut | Verdict

In summary, the half-life of phenibut is 5.3 hours. Your test subjects can expect to feel the effects of phenibut about one to two hours after taking it. The peak effects often last about four to size, with residual effects lasting as much as 24 hours after the first dose.

Of course, the timing and intensity of effects will vary for each individual, according to individual factors like metabolism, hydration, age, and weight.



  1. Lapin I. (2001). Phenibut (beta-phenyl-GABA): a tranquilizer and nootropic drug. CNS drug reviews, 7(4), 471–481. doi:10.1111/j.1527-3458.2001.tb00211.x
  2. Cheung, J. & Penn, J. (2018). Weekly dose: Phenibut. The Conversation.
  3. Koob, G. F. (1996). Drug addiction: the yin and yang of hedonic homeostasis. Neuron, 16(5), 893-896.
  4. Ozon Pharm (n.d.), Fenibut (PDF). [In Russian].
  5. CDC (2020). Notes from the Field: Phenibut Exposures Reported to Poison Centers — United States, 2009–2019
  6. Owen, D. R., Wood, D. M., Archer, J. R., & Dargan, P. I. (2016). Phenibut (4‐amino‐3‐phenyl‐butyric acid): Availability, prevalence of use, desired effects and acute toxicity. Drug and alcohol review, 35(5), 591-596.
  7. Chutko, L. S., Surushkina, S. I., Iakovenko, E. A., Nikishena, I. S., Anisimova, T. I., & Bondarchuk, I. L. (2014). Cognitive and emotional impairments in patients with protracted anxiety-phobic disorders. Therapeutic archive, 86(12), 61-65.
  8. Zyablitseva, E. A., Kositsyn, N. S., & Shul'gina, G. I. (2009). The Effects of Agonists of Ionotropic GABA A and Metabotropic GABA B Receptors on Learning. The Spanish Journal of Psychology, 12(1), 12-20.
  9. Tyurenkov, I. N., Borodkina, L. E., Bagmetova, V. V., Berestovitskaya, V. M., & Vasil’eva, O. S. (2016). Comparison of Nootropic and Neuroprotective Features of Aryl-Substituted Analogs of Gamma-Aminobutyric Acid. Bulletin of experimental biology and medicine, 160(4), 465-469.
  10. Ahuja, T., Mgbako, O., Katzman, C., & Grossman, A. (2018). Phenibut (β-phenyl-γ-aminobutyric acid) dependence and management of withdrawal: Emerging nootropics of abuse. Case reports in psychiatry, 2018.

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