I saw the OP's other post, but since this is receiving the most replies, I will post here. Phenibut has recently been demonstrated (contrary to the initial Soviet pharmacological analyses) to function through not just one mechanism-of-action (at GABA -B Receptors), but three primary distinct actions which lead to it's overall pharmacological profile. (The being GABA -B Receptor agonism, TAAR1 ("Trace Amine-Associated Receptor 1" antagonism - inhibiting the action of endogenous phenethylamine), and it's gabapentinoid action as an inhibitory modulator at Voltage-Gated Ca+ channels throughout various neuronal systems.
First of all, does your friend have any history of mental illness, or is his taking any drugs for conditions such as Bipolar Disorder, Schizophrenia, Borderline Personality Disorder, or even depressive or anxiety conditions? I know that everybody is not comfortable taking about these subjects, but it is very important.
Since some gabapentinoid drugs such as Gabapentin do act in a similar way as Phenibut (in regard to it's inhibitory action at a2o-subunit containing Voltage-Gated calcium channels), I would absolutely recommend at least short-term dosing with either Gabapentin or Pregabalin (Lyrica) to address that aspect of Phenibut's pharmacology. As far as the GABA -B Receptor agonism, Baclofen is really the only commercially available GABA derivative that is selective for the GABA -B Receptor, and will not cause intense sedation, noteworthy habit-formation, and impaired cognition like benzodiazepine drugs often do. Now, I am obviously not his psychiatrist, and cannot advise him to discontinue a benzodiazepine if his psychiatrist believes that it is going to help some of the borderline paranoid delusions, I am simply stating that there are alternatives that he may want to discuss with his doctor. Tell his to be as honest as possible about everything that he is experiencing and taking to cope with it.
Are you saying that he is taking St, John's Wort on top of SSRI? This I do not advise at all, and is dangerous, and can exacerbate his symptoms. The closest pharmacological mechanism(s) of action that St. John's Wort is responsible for is most comparable to the Tricylcic Antidepressants, like amitriptyline, and their co-administration can lead to serious conditions such as Serotonin Syndrome, since they too affect the reuptake of serotonin.
The drug that I would seriously press his doctor for is Pregabalin (Lyrica). In addition to acting as a much stronger a2o-subunit Ca+ channel inhibitor, it also has much greater affect on the biosynthesis of GABA compared to Gabapentin.
Also, although I generally feel that this class of drugs is way over-prescribed by psychiatrists (mostly for anxiety, for which it has no direct correlation to), he may want to consider a dopamine antagonist anti-psychotic drug, just for the time being, until his neurochemistry has normalized itself. It is one thing if he is having delusions that he acknowledges as delusions and can ignore them. Unfortunately, these conditions can become severe quickly, and may lead to him harming himself or others in a psychotic episode. I hate to make recommendations regarding this particular class of drugs, since I do agree with the wide use of many of them, for many of the conditions for which they are prescribed for, except for in legitimate cases of schizophrenia or acute mania. However, if he is experiencing vocal hallucinations and paranoia, then he qualifies as somebody at least in short-term need if these symptoms persists. There are "old-school", first-generation, "typical" anti-psychotic drugs, and there are newer "atypical" agents that carry less central side-effects, although conflicting data exists on how they compare. I have my primary "go-to's" when the situation truly warrants it, but I will refrain from making any recommendations in the absence of the psychiatrist treating him.
I really wish that I could apply for a Compassionate Approval Exception (exceptions granted for experimental drugs not yet approved by the FDA) for one of our experimental compounds such as Phenigabine, which operates under very similar pharmacological mechanism(s)-of-action to Phenibut, yet not as "abusable". However, until our clinical trials are reviewed and vetted by the US FDA, that is simply not possible at the moment.
In most cases, these incidents are caused by the abrupt chemical imbalance, and do remedy themselves in time. Although supportive medication under the supervision of a psychiatrist is a must at this stage. In rare, severe incidents, these events serve as catalysts that exacerbate or hasten the onset on mental illness that may be passed genetically, and that likely would have occurred in some form anyway, eventually. (Although, I have my doubts that this is the case). How old is your friend? Has he had a physical, bloodwork, etc? Does he take anything recreationally, and does he have any history of any mental illness? Please provide a full list of the medications that he is now taking, including doses, and frequency of dosing. I would hate to see somebody permanently affected by a chemical imbalance, or the psychological toll that such an imbalance may exacerbate.
Without running diagnostics, meeting him, and spending time analyzing everything that led up to this, I am hesitant to make any recommendations. However, the combination of Pregabalin (Lyrica) and Baclofen addresses a good 92%+ of Phenibut's pharmacological mechanism(s)-of-action, and should stave off withdrawal syndrome - especially when coupled with a benzodiazepine such as clonazepam (which although is a GABA -A agonist and not a GABA -B agonist like Phenibut, effectively suppresses withdrawals and can tackle the additional, rebound anxiety). If the delusional thoughts and paranoia continue, I would consult his psychiatrist from a small, titrating dose of some sort of dopamine antagonist anti-psychotic drug (temporarily) - (I would, however, avoid drugs like Risperidone which also acts as a 5-HT (serotonin) Receptor antagonist at various sites, which may exacerbate depression, which under the current situation, is not a good idea).
It's been a massive pain in the a$$ that our main website is down at the moment, but many people frequently contact me via email (or, you or your friend could PM me here), and, I generally don't do this, but if things become more severe, you may call our main facility phone, and I will speak with you directly. You said that this started while he was still taking Phenibut? At what dosage? My educated opinion is telling me that there is more to this story, and that there may be more going on here, but it's difficult to say until I hear more.
-J. Gona
Psychopharmacologist
Psychotropic Treatment Specialist
Oracle Laboratories
NeuroPsych Institute