In my view, while Phenibut is a Gabapentinoid, it is notably different then both Pregabalin and Gabapentin (both of which are very similar).
Phenibut in my opinion is closer in some ways to a muscle relaxant, having some of the properties of Baclofen (Gaba B receptor agonist activity). It also builds tolerance more quickly then other Gabapentinoids in my view. It’s duration of action is longer, but it takes about twice as long for the effects to kick in, so that delay can cause you to redose too soon and overdo it. ALL three drugs bind to the a-subunit, causing anti-anxiety and anti-seizure effects.
Do I think it’s overly harmful? Not in standard doses, but I *do* think it’s safety profile is inferior to Pregabalin. I also feel it’s effects are inferior by comparison, possibly due to its poor blood brain barrier crossover (Gabapentin is notably better here, which is why a much smaller dose is effective).
I see it in the same way that I do cough syrup compared to gold standard ketamine. One *does the job* while the other is notably safer, with more medical effects, uses, and euphoric effects.
I think Phenibut (obviously using responsible doses), is ok for occasional use, for example on the weekends over a solid period of time. However, I would *STRONGLY* caution against frequent daily use. Sudden withdraw after using for multiple weeks can cause not only similar effects to Pregabalin withdraw, it can also cause a baclofen-like withdraw. Because of its activity at the Gaba B receptor, this could be very unpleasant and at high doses over time, a sudden withdraw could be dangerous too.