Issac Thorne

Last Updated February 12, 2022

You have heard about the potential benefits of phenibut, but you might be confused about:

Phenibut HCL vs. Phenibut FAA

What’s the difference between these two forms of the same compound?

Phenibut has burst onto the nootropic research scene due to its potential to reduce social anxiety and act as a cognition enhancer.

But some researchers get confused by the two different types of phenibut: HCL and FAA. In fact, the two are sometimes taken differently, have different dosing recommendations, and are not typically priced the same.

This guide on the differences between phenibut FAA vs. HCL intends to help you determine which might be the better option for your research.

Let’s get to it.

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What Is Phenibut?

To understand the difference between phenibut HCL vs. phenibut FAA, we first have to know a bit about phenibut itself.

Phenibut is a neuropsychotropic drug with anxiolytic and nootropic properties [1].
Chemically, phenibut is similar to GABA, a neurotransmitter that is common throughout the nervous system. Due to this similarity, phenibut binds to the GABA receptors—primarily to the slower-acting GABAB receptors [2, 3].

Since phenibut binds to the same receptors as GABA itself, it can produce GABA-like effects. GABA is known as the body’s inhibitory neurotransmitter—the transmitter that reduces excitability in neurons. Other neurotransmitters turn “on” the neuron when they are needed to send a signal, and then GABA turns them “off” when that signal is no longer needed.

Some of the signals that GABA turns “off” are the signals for stress. If a person did not have GABA, their brain might be constantly wired and experiencing stress. GABA helps turn off those signals so that they do not become a burden.

Phenibut effects

Great, so phenibut inhibits neurons and lowers some types of brain activity. But what do test subjects experience when they consume phenibut? Well, in certain adult populations, phenibut has been shown to produce a variety of effects, including [1, 2, 4, 5]:

  • Reduced feelings of stress and anxiety
  • Less social anxiety and increased sociability
  • Better sleep
  • Cognitive enhancement and better focus
  • Boosted mood
  • Feelings of euphoria

We reiterate that the research available has largely been conducted on small samples, often including patients with medical conditions and psychological disorders [1]. Most of the research has been published in the Russian language [1].

But there has been enough research on the effects of phenibut to warrant its approval as a prescription medication in several countries, including Russia, Belarus, and Latvia. In these countries, phenibut is prescribed for a number of conditions, including anxiety, insomnia, PTSD, and alcohol use disorder.

In the United States, however, phenibut is classified as a “New Drug” under the Federal Food, Drug, and Cosmetic Act (FD&C Act). In other words, phenibut has not been fully reviewed or approved for any use by the FDA.


Phenibut Side Effects and Safety

We know that phenibut has a number of intriguing potential effects and is worth further study. But can we regard it as safe for research participants?

If used properly, phenibut is well-tolerated by most individuals [1].

Nonetheless, there are some risks of which nootropic researchers should be aware. If test subjects take too much phenibut or take it too frequently, they’re at higher risk of experiencing these adverse effects.

Side effects of phenibut

Since it’s prescribed as a drug in several countries, we know a good deal about phenibut’s side effects and uses.

The possible side effects of phenibut include [2, 6]:

  • Drowsiness
  • Nausea
  • Irritability
  • Headache
  • Sedation

Less common phenibut side effects include [6]:

  • Motor incoordination
  • Hangover-like symptoms
  • Loss of balance

Additionally, some individuals can experience allergic reactions to phenibut [6], which is a response from a person’s immune system to the substance. Allergic reaction effects of phenibut may include a rash or itching. These are relatively rare but can still occur.

To avoid or mitigate the risk of side effects in their human subjects, phenibut researchers are advised to design study protocols that ensure all test subjects receive an appropriate dose. Further, researchers are advised to educate their subjects on how to use phenibut properly.

For example, researchers can start test subjects off with a small dose to gauge the effects and reaction, and then build up from there. They can further exclude allergy-prone test subjects from their phenibut research.

Overdose effects

Another phenibut-related concern is ensuring that the subject does not take too large of a dose.

In the United States, there has been at least one death reported in a poisoning where phenibut was the only drug or agent involved [7]. However, neither the circumstances surrounding the death, nor the amount of phenibut that the deceased individual had actually ingested, were reported to the public.

In the medical literature, even extreme doses sustained over multiple did not prove lethal. In one particular case, a man had been ingesting 20 grams/day of phenibut and began suffering from hallucinations and confusion as of the third day following withdrawal. The man’s symptoms resolved after he was treated with benzodiazepines [4].

These reports demonstrate that phenibut overdose is a major concern; symptoms associated with ingesting too much phenibut include [6]:

  • Severe drowsiness
  • Nausea
  • Vomiting
  • Lowered blood pressure

Given the severity of a potential phenibut overdose, it is critical that researchers stick to appropriate phenibut dosage guidelines. As a rule of thumb, the maximum single dose for most test subjects should be 750 mg with a maximum daily amount of 2.5 g. These are in line with the dosing guidelines set forth by a Russian manufacturer of the prescription medication [6].

Interaction effects

Researchers and subjects must also understand how phenibut could interact with other conditions or medications.

Since phenibut is a nervous system depressant, it should not be taken in combination with other depressants. Accordingly, your test subjects should not take phenibut with alcohol, benzodiazepines, and anticonvulsants.

Researchers should consider excluding test subjects who are pregnant or breastfeeding, since the effects of phenibut on infants or fetuses are unknown at this time [6].

Phenibut dependence

Certain individuals can develop phenibut tolerance and dependence [3, 4]. There are cases—mostly isolated—of extreme dependence and the associated withdrawal systems following phenibut abuse [8, 9].

Phenibut withdrawal effects can be very unpleasant and can include:

  • Rebound anxiety
  • Anger
  • Agitation
  • Irritability
  • Insomnia
  • Auditory and visual hallucinations
  • Psychosis

Again, there are many precautions that a researcher may take to ensure that their test subjects do not become dependent on phenibut.

For example, they can limit the frequency of use, setting a maximum like one or two times per week. Discontinuing use for some time following regular use (e.g. cycling) is also advised. Finally, the lower the dose, the lower the likelihood that a test subject will develop phenibut dependence.

Phenibut safety guidelines

To sum up, researchers can look to these general guidelines when designing their study protocols:

  • Start with a low dose to gauge the effect on test subjects. You can increase the dose later, if appropriate;
  • Test subjects at risk of allergic reaction should refrain from taking phenibut;
  • They should not take more than 750 mg of phenibut in a single dose;
  • They should not take more than 2.5 g of phenibut in a single day;
  • They should not take phenibut more than one to two times per week;
  • They should not take phenibut with other depressants like alcohol, benzodiazepines, or anticonvulsants;
  • They should not take phenibut if they are pregnant or breastfeeding;
  • Subjects should cycle off phenibut following protracted use.

By referring to these general guidelines, researchers can better ensure their human subjects a safe phenibut experience.

Phenibut HCL | Beginner’s Guide

Now that we have a basic understanding of phenibut research safety, let’s now go over the two common forms of the research compound: phenibut HCL and phenibut FAA.

Phenibut HCL is the more popular of the two, so let’s cover it first.

-> What is it: Phenibut HCL is made up of phenibut (an amino acid chain) and hydrogen chloride (HCl). Together these molecules form an ionic salt.

Phenibut HCL’s “ionic salt” form means that it can be easily dissolved in liquids, like water. In fact, dissolving phenibut HCL in water is a popular way to administer it in nootropic research. Phenibut HCL usually comes in the form of white powder, but may also come in the form of fine or large crystals—all of these options are equally soluble.

-> Price: You might notice that phenibut HCL is usually cheaper than phenibut FAA. The reason for the cost discrepancy is likely due to a comparatively lower concentration of phenibut in its HCL form. Still, some researchers report that, even with the slightly higher dose needed from HCL for the same results (see below), the HCL does end up being a bit cheaper overall.

-> Dose: Because it may have a lower concentration of phenibut compared to FAA, HCL doses may need to be adjusted upward for the same effect. The prevalent opinion is to first set an HCL dose, and use about ⅔ of that for FAA testing. A typical starting dose for phenibut HCL in nootropic research may look like:

  • 350 mg to 500 mg
  • split into 1 to 3 doses day
  • 1-2 days a week, maximum
  • taken on an empty stomach

Depending on the purpose of your research, you may also consider “microdosing,” with doses starting from 100 mg.


How To Take Phenibut HCL

There are two common ways to take phenibut HCL:

  1. Dissolve it in a drink. Water is common. Juice is also common because it takes away the bitter taste. Some test subjects might even prefer to mix it with coffee. Provided you’re working with a powder, you’ll simply need to measure out the correct dose and put it in the drink (the warmer, the better it dissolves).
  2. Phenibut capsules. These are very common in nootropic research. The capsules are usually pre-filled, so test subjects need to worry about measuring out the correct amount.

Phenibut HCL should not be dissolved under the tongue. It is highly acidic, so it has a bad taste and may damage the teeth.

Phenibut FAA | Beginner’s Guide

Phenibut FAA is not as popular as the HCL form, but it may be appropriate for your research.

-> What is it: Phenibut FAA stands for “phenibut free amino acid.” This type usually comes as a phenibut powder, and it’s not acidic like HCL. Since it is not ionic, it does not tend to be as soluble as phenibut HCL.

-> Price: You’ll notice that phenibut FAA tends to be slightly more expensive than the HCL version.

-> Dose: Subjects will usually need less FAA than HCL because the former is more concentrated. A starting dose for phenibut FAA in nootropic research might be:

  • 250 mg to 350 mg
  • split into 1 to 3 doses day
  • 1-2 days a week, maximum
  • taken on an empty stomach

Again, you might also consider “microdosing,” with doses starting from 100 mg.

How To Take Phenibut FAA

Nothing too complex here…

  1. Phenibut FAA is commonly taken sublingually. That means placing it under the tongue where it can be absorbed directly into the bloodstream. This method may be faster-acting, but the strong bitter taste may turn your test subjects off.
  2. Ingested. Some test subjects do try to dissolve it in a drink, but it may be slow to dissolve. You may also try putting it in dissolvable paper or inserting it into capsules.
    As with phenibut HCL, test subjects should take phenibut FAA at least one hour before eating. It works best on an empty stomach.

Phenibut HCL vs. FAA

What are the similarities and differences between them? We’ve made a list for easy reference.


Here are the similarities between phenibut HCL and phenibut FAA:

  • Have the same effect on the body;
  • Both have phenibut as the main active ingredient;
  • The “phenibut” is the same; it’s chemically identical;
  • They should both be taken on an empty stomach.


Here are some of the differences between phenibut HCL vs. FAA:

  • Phenibut HCL tends to be cheaper than phenibut FAA;
  • Phenibut HCL may require a larger dose compared to phenibut FAA;
  • Phenibut HCL tends to be highly soluble, whereas phenibut FAA tends to be clunkier when placed in liquid;
  • Phenibut HCL is best taken in a drink; phenibut FAA may be taken in capsule, a drink, or sublingually.

Which One Is Better?

To be honest, neither HCL nor FAA is clearly “better” for nootropic research. The choice may come down to preference and product availability.

That said, phenibut HCL appears to be the more popular option for research purposes.

Phenibut HCL

HCL may be more popular due to its relative cost effectiveness and solubility. After measuring out their correct dose, test subjects may easily mix phenibut HCL into their drink of choice.

That’s not to say that phenibut FAA is inappropriate for research—you can absolutely use it. We just find that HCL’s relative cost advantage and ease of administration do play a role over the long term.


Buy Phenibut Online | 2022 Guide

By now, you might want to get started on your research by buying either phenibut HCL or phenibut FAA.

If you’re a researcher based in the United States or another country where phenibut is an unregulated compound, you can legally buy phenibut online.

But not all phenibut vendors are created the same. We’ve had our own issues with impure products and unresponsive customer service. Luckily, we’ve tried out several pharmaceutical-grade phenibut sellers, and can ultimately recommend:

Here’s why we love this vendor:

  • They offer high-quality phenibut HCL and FAA in powder form;
  • All of their phenibut is batch and lot coded, and they provide lab reports to ensure quality and transparency;
  • Their phenibut is lab-tested for purity to ensure the absence of any adulterants, excipients, and flow agents;
  • They offer fast and convenient shipping within the USA and internationally;
  • Last and certainly not least, their pricing is extremely competitive: a 50g jar of phenibut HCL powder currently costs $24.99, while their 50g FAA powder is now $29.99.

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Phenibut FAA vs. HCL | Verdict

You can go with either one for your phenibut research

We prefer phenibut HCL for research primarily thanks to its lower cost and better solubility. If you’re a phenibut researcher, you may well try both and see which works better for your purposes.

Whether you ultimately choose FAA or HCL, you cannot go wrong either way.


  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. 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. doi:10.1155/2018/9864285
  4. Högberg, L., Szabó, I., & Ruusa, J. (2013). Psychotic symptoms during phenibut (beta-phenyl-gamma-aminobutyric acid) withdrawal. Journal of Substance Use, 18(4), 335-338.
  5. 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.
  6. Ozon Pharm (n.d.), Fenibut (PDF). [In Russian].
  7. CDC (2020). Notes from the Field: Phenibut Exposures Reported to Poison Centers — United States, 2009–2019.
  8. Samokhvalov, A. V., Paton-Gay, C. L., Balchand, K., & Rehm, J. (2013). Phenibut dependence. Case Reports, 2013, bcr2012008381.
  9. Hardman, M. I., Sprung, J., & Weingarten, T. N. (2019). Acute phenibut withdrawal: A comprehensive literature review and illustrative case report. Bosnian Journal of Basic Medical Sciences, 19(2), 125.

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