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How long does Phenibut last?

How long does it take to feel Phenibut?

According to experiences posted on Erowid.org, Phenibut usually takes around 60 to 90 minutes to feel the first effects. The full dose will usually only be felt around 2 hours after taking Phenibut. This is backed up by user reviews on the internet. People are aware that Phenibut has a fairly long onset time. The effects of Phenibut also last quite long.[1]



How long do the main effects of Phenibut last?

At low to medium doses, Phenibut’s main effects are a feeling of well-being, stress reduction, relaxation, and a slight increase in sociability. At higher doses, these effects are more noticeable with the extra alcohol-like effects such as pain-relief and easy, healthy sleep. Other effects include increased memory and learning abilities, and protection of the brain and heart from stress. Duration of the main effects of an average dose is around 4 – 5 hours, depending on the user’s metabolism and other factors. Higher doses will typically last longer than lower dosages.[2]


What is the ‘half-life’ of Phenibut?

A chemical or substance’s half-life is the average amount of time taken for the substance to lose half of its effects in the body. So, if you take 500mg of Phenibut, then the half-life is the amount of time until you can only feel half the effects – or roughly the same effects as a 250mg dose. Clinical studies in Russia have found the average half-life of Phenibut to 5.3 hours, at doses of 200mg and 500mg. This helps us to understand why the main effects of Phenibut are usually felt for around 4-5 hours.[3]

Does Phenibut have side-effects?

Early clinical studies of Phenibut did not find any side effects reported in low to medium doses. Now that Phenibut is more widely available, there are some reports of side effects which include: more vivid dreams, numbness and aching joints. At higher doses side effects may include dizziness and drowsiness. The main side-effect to watch out for is a tolerance build-up. Phenibut has a half-life of 5.3 hours, but it can remain in the body for days. This is why it’s recommended to only use Phenibut two days per week, to prevent tolerance build-up.[4]

Is there withdrawal from Phenibut use?

According to the Encyclopedia of Mind Enhancing Foods, Drugs and Nutritional Substances, as of 2015, there has only been one medical case of withdrawal symptoms from Phenibut. There are some personal reviews of withdrawal symptoms from prolonged use of high doses of Phenibut. These symptoms included anxiety and nervousness, dizziness, irritation and loss of appetite, among others. Taking Phenibut in the lowest possible dose and correctly cycling its use should prevent a tolerance build-up and prevent withdrawal effects.[5] Check out our Ultimate Phenibut Guide!


This is NOT a dietary supplement. Handle with care. Not intended to treat, diagnose, or cure any disease or ailment. Use with CAUTION. When taken inappropriately, Phenibut can cause serious adverse effects. Keep out of reach of children. Please read and fully understand associated risks before using. This product has not been approved by the FDA.


[1] Phenibut basics by Erowid, https://www.erowid.org/smarts/phenibut/phenibut_basics.shtml, retrieved 20-05-2016

[2] How long does phenibut last? by James Smoot https://smartdrugsforcollege.com/how-long-does-phenibut-last/, retrieved 20-05-2016

[3] HISTORY OF DRUG DEVELOPMENT – Phenibut, Lapin, 2001, CNS Drug Reviews Vol. 7, No. 4, pp. 471–481

[4] Phenibut Side Effects, Tolerance and Withdrawal Risk by Nootriment editorial staff, retrieved 20-05-2016

[5] Encyclopedia of Mind Enhancing Foods, Drugs and Nutritional Substances, 2nd edition, McFarland, 25 Feb 2015, David W. Group, p 186.