The final word Guideline to GBL: Gains, Works by using, and Safety Recommendations ???? ???? Precisely what is GBL? GBL (Gamma-Butyrolactone) is really a chemical compound commonly used in industrial and pharmaceutical programs. It's a precursor to GHB (Gamma-Hydroxybutyrate), a compound known for its sedative and euphoric results. GBL is often lo