Phenibut—also “β-phenyl-γ-aminobutyric acid” or “4-amino-3-phenylbutyric acid HCl”—is found as an ingredient in some dietary supplements. These supplements are sold for a variety of uses, including sleep, stress reduction, and nootropic (“smart pill”) effects. Phenibut is a drug developed in Russia and Latvia, where it’s used as to treat anxiety, alcohol withdrawal, insomnia, and other conditions.

FDA recently announced that phenibut “is is a substance that does not meet the statutory definition of a dietary ingredient.” As a result, phenibut is now on the OPSS list of DoD-prohibited substances. Phenibut is a synthetic substance—it’s made in a laboratory and doesn’t occur in nature—which means it doesn’t fit FDA’s definition of an acceptable dietary supplement ingredient. It’s similar to the FDA-approved drug baclofen.

There are reports of adverse events associated with phenibut use, and some evidence suggests that continued use can lead to dependence and increased tolerance, which means an increasingly higher dose is needed for the same effect. Withdrawal symptoms include visual and auditory hallucinations, muscle pain and twitching, heart arrhythmia (tachycardia), nausea, vomiting, insomnia, sensitivity to sound and light, and separation from reality.

Updated 19 April 2019


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