Phenibut supplement side effects, tolerance and withdrawal symptoms, dose and dosage, caution, danger, adverse reactions, addiction, capsules, powder by Ray Sahelian, M.D.
Role in anxiety, sleep, sedation, benefit as a relaxant
September 11 2014

Phenibut is a new supplement to the health industry in the United States. Research has been conducted in Russia but little knowledge exists in Western medicine regarding its properties and effects of long term use. Phenibut is widely used in Russia to relieve tension, anxiety, and fear, to improve sleep in psychosomatic or neurotic patients or regular individuals with insomnia, as well as a pre- or post-operative medication. It is also used in the therapy of disorders characterized by asthenia and depression, as well as in post-traumatic stress, stuttering and vestibular disorders. Phenibut, chemically known as β-Phenyl-γ-aminobutyric acid, is a derivative of GABA brain chemical. It acts primarily at GABA (B) and, to some extent, at GABA (A) receptors.

Medical uses, which conditions does it help?
Anxiety and tension relief - phenibut is taken during the day
Sleep or insomnia - phenibut is taken an hour or two before bed.

What you are likely to feel
Most users feel a sense of calmness a few minutes or an or two after taking some of the powder or a capsule. If taken in the evening there is a gradual onset of sleepiness.

Tolerance, how to avoid
Regular users of phenibut, especially in high dosages, can build a tolerance to this anti-anxiety and sleep aid, and may require more over time to be effective. Therefore, as with most medications, it is a good idea to use it less frequently and to substitute other natural products.

Alternative natural sleep aids that can be used on the evenings when not using phenibut powder or capsule:
Good Night Rx all natural sleep aid.
Melatonin pineal hormone
Theanine amino acid which has sedative properties.
5-HTP serotonin precursor
Passion Flower herb
Hops herb in a capsule or tea.
GABA supplements have an influence on some people.
Valerian herb is liked by some people but it has not worked well for me.
Lean more about natural ways to help relieve insomnia. Most importantly take a brief morning walk with light exposure to set your circadian clock and be physically active during the day. Also, if you have sleep problems, avoid caffeine and tea, even herbal teas can build up in the body and over time begin to cause alertness and shallow sleep.

Dose and dosage
Each person is different on the dose they respond to and I am still in the process of reviewing data to determine a safe dose for long term use. The higher the dosage used, the more likely tolerance and adverse reactions will develop. I am still trying to figure out whether it works better with or without food, I suspect it works better on an empty stomach or with a small snack.

Phenibut side effects, concerns, danger
Thus far I am aware of the following side effects but I am still learning about these, I plan to update this information over time:

Sedation, which is desirable if that is the intent of supplementation.
Grogginess along with low motivation if high dosages are used.
Constipation with regular use.
Loss of sex drive and difficulty with erection and reduction of sensation. Impotence or erectile dysfunction can occur which should be reversible upon stopping use. The loss of libido should be reversed after stopping the medication. I am still not fully sure about this but my initial impression is that it has a negative effect on sexuality.
   Email July 2014: Q. I noticed you listed erectile dysfunction and loss of libido as potential side effects. I've been taking phenibut once weekly for a year and I few months with no side effects, but recently I have been experiencing those sexual side effects. I have anxiety and depression on and off, and I know that those conditions can affect libido as well. The sexual side effects aren't listed on the manual for the pharmaceutical version of phenibut Noofen. Is it possible for it to take over a year for these side effects to manifest? I keep it in moderation and only use it once a week at around 2 grams.
   A. I am still learning about the influence of phenibut on erectile function and libido.
Blurred vision or difficulty with focusing.

I am also uncomfortable with its use during the day, especially if driving a car or operating machinery. It is a good idea to avoid drinking alcohol together with phenibut.

Email September 2014, positive and negative effects
I wanted to post an email to your informational page about the OTC GABA supplement phenibut. I just wanted to report my experience with using the supplement on your page as I saw some other emails from people. I had many positive effects from using it but also many negative side effects from using it which grew severe enough to stop taking it so I thought it be important to report my experience. I am familiar with the dosages and I wasn't taking all that much (maybe 2-3 grams a day) but I was using the powered form and dissolving it in water so perhaps it was highly purified and strong. It definitely has cumulative effects and a long half-life because as the days went on, it's effects grew stronger and lasted all day.
The positive effects I experienced were: -marked elevation in mood to the point of euphoria -improved quality of sleep -enhanced appreciation for music -improved focus and cognition initially but that became memory difficulty -marked relief of anxiety -increased motivation -renewed interest in things -being more talkative.
The negative effects I experienced were: -the memory problems I mentioned -ataxia -periods of severe dizziness that would come on suddenly and last for an hour or more -akathisia -nausea and I did vomit once after eating -sudden deep and sharp pains in my limbs that would last for several minutes -a hangover like feeling upon waking -sensitivity to temperature changes -and the most disturbing side effect I experienced that I thought need to be reported was that I developed psychosis and became delusional. I had to temporarily take anti-psychotics until the drug cleared out of my system.

There have been reports of phenibut withdrawal with symptoms of insomnia, lack of appetite and mood changes. If you have been taking it for prolonged periods, reduce your dosage each night as part of the tapering process.

Dependence and habituation, addiction
Some people can get easily dependent on this supplement and will have an urge, or need, to use it nightly. Avoid the urge to use it regularly, at thus avoid the potential of addiction and dependence.

BMJ Case Rep. 2013. Phenibut dependence. Phenibut is a γ-aminobutyric acid (GABA) agonist designed and used as an anxiolytic in Russia. In Western countries, it is not a registered medication but is available through online stores as a supplement. We present a case of a patient who used phenibut to self-medicate anxiety, insomnia and cravings for alcohol. While phenibut was helpful initially, the patient developed dependence including tolerance, significant withdrawal symptoms within 3-4 h of last use and failure to fulfil his roles at work and at home. He finally sought medical assistance in our addictions clinic. We have gradually, over the course of 9 weeks, substituted phenibut with baclofen, which has similar pharmacological properties, and then successfully tapered the patient off baclofen. This required approximately 10 mg of baclofen for each gram of phenibut.

When to take, how many hours before sleep?
If you are very alert you may need to take it a couple of hours before you go to bed. If you are not in a normal tired state but you think you will have trouble sleeping that night, you can take it about an hour before bed.

How long do the effects of phenibut last?
Most people notice the effects for a few hours, and this depends on a person's sensitivity and the dosage taken. The higher the dose, the longer the effects.

Phenibut Research
Effect of phenibut on the behavior of experimental animals under conditions of voluntary chronic alcoholism
Eksp Klin Farmakol. 2005.
The effect of phenibut on the locomotor and orientation-research activity, as well as on the alcohol and food motivation, was studied on experimental animals under conditions of voluntary chronic alcoholism. Phenibut decreased the manifestations of alcohol-induced behavioral disorders and reduced alcohol motivation.
   Apparently, the limited research with phenibut indicates it has a role to play in alcohol misuse.

Effect of the GABA derivative phenibut on learning
Vestn Ross Akad Med Nauk. 2005.
The learning effect of phenibut, a beta-phenyl derivative of the inhibitory neuromediator GABA, used in a subcutaneous dose of 40 mg/kg 2 hours before each experiment, was studied in rabbits. The injection of phenibut was shown to enhance not only the inhibitory, but also excitatory components of cerebral cortical neuronal responses to all applied stimuli. The findings support the concept that the GABAergic neuromediator system is involved in the elaboration of internal inhibition and explain the sense of intracerebral processes that ensure both the sedative properties of phenibut and its ability to improve patients' systemic tone and health status when brain dysfunctions are treated.

Cardiac effects of fenibut in development of experimental chronic renal insufficiency
Eksp Klin Farmakol. 2003.
St. Petersburg State Medical University, St. Petersburg, Russia.
The effect of fenibut on the mechanical activity of myocardium was studied in vitro and in vivo in rats with experimental chronic renal insufficiency (CRI) in a regime of physiologically alternating load simulating the intact heart function. The administration of fenibut (10 mg/kg) in rats after nephrectomy prevents the development of myocardial hyperfunction (characteristic of the animals with CRI in stage 1). In in vitro experiments on isolated myocardium fenibut also decreased the myocardial hyperfunction and reduced contractility to a control level, which was accompanied by accelerated relaxation in all finite systolic lengths.

Anti-arrhythmic properties of GABA and GABA-ergic system activators
Eksp Klin Farmakol. 2002.
Clinical and experimental data available in the literature are summarized, which are indicative of the antiarrhythmogenic properties of GABA and substances possessing GABA-positive activity (phenibut, piracetam, sodium hydroxybutyrate, lithium hydroxybutyrate, etc.). The antiarrhythmic effects are manifested in various cases of the heart rhythm violation. The mechanism of this action is related to activation of the central and peripheral retarding GABAergic system, as well as to antihypoxant, antioxidant, and antistressor effects.

Phenibut (beta-phenyl-GABA): a tranquilizer and nootropic drug.
CNS Drug Rev. 2001.
Phenibut (beta-phenyl-gamma-aminobutyric acid HCl) is a neuropsychotropic drug that was discovered and introduced into clinical practice in Russia in the 1960s. It has anxiolytic and nootropic (cognition enhancing) effects. It acts as a GABA-mimetic, primarily at GABA(B) and, to some extent, at GABA(A) receptors. It also stimulates dopamine receptors and antagonizes beta-phenethylamine (PEA), a putative endogenous anxiogenic. The psychopharmacological activity of phenibut is similar to that of baclofen, a p-Cl-derivative of phenibut. This article reviews the structure-activity relationship of phenibut and its derivatives. Emphasis is placed on the importance of the position of the phenyl ring, the role of the carboxyl group, and the activity of optical isomers. Comparison of phenibut with piracetam and diazepam reveals similarities and differences in their pharmacological and clinical effects.

Q. Great Site! Kudos to the doctor. I encourage you to keep writing more info on phenibut, a modified version of GABA that crosses the blood brain barrier. I find it VERY effective to reduce generalized anxiety disorder for short term use. The most effective anxiety reducer of any non-benzo I've tried.

Q. Glad to see you've now added a profile for phenibut. I wanted to give my experiences with this medicine in the hope that it might help anyone out there wondering how well it works. I suffer from generalized anxiety disorder and I must say phenibut at a high dose of 2 grams absolutely kills the anxiety. Lower doses have smaller effects. The effects make themselves apparent at 1-2 hours after oral dosing and last for perhaps 4-5 hours. It does a good job at reducing anxiety, it is however a SHORT TERM solution only. Tolerance seems to develop within days with continuous dosing (which takes about 2 weeks of complete abstinence from phenibut to disappear) and it is therefore best to use sparingly, perhaps once a week during particularly bad episodes of anxiety. This kind of frequency of use does not seem to develop tolerance. At the relatively high dose of 2 grams it does make me drowsy and nauseous after approximately 4-5 hours. A hangover and some rebound anxiety is expected the next day, leaving me to question the point of this drug. It's a shame because its anxiolytic effects are absolutely fantastic, but the hangover, rebound anxiety and nauseous feeling seem to leave you feeling pretty bad the day after. I've been reading up on phenibut since it appeared on the market and the above experience seems to echo what a lot of people are describing (in terms of hangover, rebound anxiety, tolerance) so they aren't side-effects isolated to me only. People are using anywhere from 250mg - 2,000mg to induce an anxiety reducing effect.
   A. Thank you so much for sharing this experience with us.

I have been using this Russian nootropic and anxiolytic on and off for along time now, with varied effects, and to the extent at one point that withdrawal was a very miserable experience. Everyone is different and while it's great for me for anxiety, if I'm not able to taper off of it the withdrawal is pretty bad for me, so it might be nice to caution everyone about it. I'm not alone, there are people who took far more and for far longer than me and many have ended up in addiction treatment scenarios similar to those who are addicted to many other forms of benzodiazepines. The real word of caution, though, should be about supplement quality. When I was using it frequently enough to feel withdrawal when I didn't use it, I noticed that between brands there was a huge variability in the true strength of the phenibut. Some gave me tics, mostly in my face and back, but some was not this way at all. Some also was definitely cut with something inert, because I could take twice my normal dose and not feel any effect; in fact it was just enough to keep withdrawal symptoms at bay in some cases. Another time, a new bottle of capsules arrived and not realizing it I took on 750mg dose (I use it pretty sparingly due to my sensitivity), and that combined with the fact that this stuff must've been really pure or uncut meant that I was really sedated and although it was enjoyable, it was unintentional and I'm glad I wasn't headed out for a drive or anything that required all of my reaction times and faculties. Anyway, I hope that helps.

FDA - Is this product legal or has the FDA removed it from the market?
   The FDA has not removed phenibut from over the counter sale as of March 2014.