Research chemicalDepressantGABA-B agonistGHB prodrugIndustrial solvent

GBL

Also known as Gamma-butyrolactone · GBL · Blue nitro

Written by enwyReviewed 15 Jul 20262 sources0 comments

GBL (gamma-butyrolactone) is an industrial solvent and a prodrug of GHB: once ingested it is rapidly converted to GHB by the body. It shares GHB's effects and its dangerously narrow dose-response, but is absorbed faster and is more potent by volume, making misdosing even easier. As with GHB, the combination with alcohol markedly raises the risk of coma and death.

01 Overview

GBL is widely available as a cleaner and solvent, which is part of why it is misused as a GHB substitute. After ingestion it is converted to GHB within minutes, so its effects, risks and dependence potential are essentially those of GHB but with faster onset and higher potency per millilitre.

That higher potency compresses an already narrow safety margin: very small differences in volume produce large differences in effect, and dosing by drops or fractions of a millilitre is required. Undiluted GBL is also caustic and can irritate the mouth and gut. Heavy, frequent use causes the same severe physical dependence and potentially life-threatening withdrawal as GHB.

02 Mechanism

A GHB prodrug: rapidly hydrolysed by peripheral lactonases to gamma-hydroxybutyrate, which acts at GHB and GABA-B receptors to depress the CNS.

03 Dosing

Tier	Dose	Route	Notes
Light	0.5–1 ml	Oral	Must be diluted; more potent per ml than GHB. Measure by fractions of a millilitre.
Common	1–1.5 ml	Oral	Effects come on within minutes; the margin above this is very small.
Strong	1.5–2.5 ml	Oral	High risk of sudden unconsciousness; do not redose before onset is complete.

04 Effects

Effect	Magnitude	Evidence
Euphoria and disinhibitionRelaxation and sociability, as with GHB, with faster onset.	dose-dependent	Observational
SedationDrowsiness progressing to deep sleep at higher doses.	dose-dependent	Observational
Rapid onsetFaster absorption than GHB, which shortens the window to recognise overdose.	within minutes	Observational

05 Side effects

Effect	Severity	Frequency	Evidence
Overdose, coma and respiratory arrestHigher potency and faster onset make overshoot and sudden coma easy; risk is greatly increased by alcohol.	Life-threatening	Common at recreational doses	Observational
Dependence and withdrawal syndromeFrequent dosing causes severe physical dependence; withdrawal can be life-threatening.	Life-threatening	With heavy, frequent use	Observational
Caustic mucosal irritationUndiluted GBL is caustic and irritates the mouth, throat and stomach.	Moderate	Common if undiluted	Observational

06 Legal status

United States

Schedule I when intended for human consumption

Treated as GHB (Schedule I) under the analogue provisions when meant for ingestion; otherwise a regulated industrial chemical. · as of Jan 2026

United Kingdom

Class B

Controlled under the Misuse of Drugs Act. · as of Jan 2026

07 References

GBL as a GHB prodrug: pharmacology and toxicityPubMed

GHB/GBL drug profileEuropean Monitoring Centre for Drugs and Drug Addiction (EUDA)

08 Discussion0 comments

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This page is reference information, not medical advice. Doses and protocols are documented as they appear in the clinical literature and in practice — describing them is not a recommendation to use them. Countermeasures listed here are not a substitute for a physician. Legal status varies by jurisdiction and changes.