F-Phenibut (also known as 4-Fluorophenibut, Fluorophenibut, Fluorobut, Baflofen and CGP-11130) is a central nervous system depressant and closely related structural analog of phenibut. F-Phenibut possesses an effect profile similar to phenibut but with a faster onset, significantly increased potency, and shorter total duration.[citation needed] It has recently become available through online research chemical vendors, although little is known about this substance, particularly its potential toxicity and addiction potential.
F-Phenibut likely has a low toxicity relative to dose. However, it is potentially lethal when mixed with depressants like alcohol, benzodiazepines or opioids.
The toxicity and long-term health effects of recreational F-Phenibut use do not seem to have been studied in any scientific context and the exact toxic dosage is unknown. This is because F-Phenibut has very little history of human usage. Anecdotal evidence from people who have tried this substance within the community suggests that there do not seem to be any negative health effects attributed to simply trying this substance at low to moderate doses by itself and using it sparingly (but nothing can be completely guaranteed).