Psychedex is in open beta. We are still fine-tuning the generation and review process. Please double-check sources.
GBL
gamma-butyrolactone
GBL (gamma-butyrolactone) — G, liquid ecstasy — is a synthetic depressant of the lactone class. It is a prodrug of GHB: the body converts it to GHB within minutes, and GHB produces every effect. GHB activates inhibitory receptors in the brain, broadly suppressing neural activity and producing sedation.
GBL (gamma-butyrolactone) — G, liquid ecstasy — is a synthetic depressant of the lactone class. It is a prodrug of GHB, distinguished by faster onset and a narrower margin of safety. GBL acts entirely through GABA-B receptors,[1][2] producing its effects by broadly suppressing neuronal excitability after enzymatic conversion to GHB in the blood.[3][4]
Psychedex is in open beta. We are still fine-tuning the generation and review process. Please double-check sources.
GHB was first synthesized in 1960 by Henri Laborit as a sedative designed to reach the brain.[1] After GHB was scheduled in 2000, users switched to GBL — still widely available as an industrial solvent, with US production estimated at 185,000 metric tons per year.[2] Today GBL is used primarily as a chemsex drug in gay and bisexual communities across Europe and Australia.[3]
Subjective effects include euphoria, disinhibition, empathogenic warmth, sexual arousal, and sedation. The experience rises to full effect in minutes — a steep rush that compresses what alcohol spreads over hours — then tips abruptly into deep unconsciousness with only a small dose increase. Nausea, dizziness, motor impairment, and memory blackouts are common unwanted effects.
GBL produces physical dependence faster than alcohol or benzodiazepines,[4] and a fraction of a milliliter separates a recreational dose from one that stops breathing. Compulsive redosing accelerates dependence within days, and withdrawal carries real risk of seizures and death. The evidence base rests largely on GHB research and clinical toxicology case reports, with significant gaps in long-term effects.[5]
History[edit]
History
Discovery
GBL has been manufactured for decades as an industrial solvent. GHB, its active form, was first synthesized in 1960 by Henri Laborit — designed as a sedative capable of crossing into the brain[1] — and entered European clinical use as an anesthetic by 1964.
Recreational emergence and scheduling
During the 1980s, GHB was marketed as a bodybuilding supplement based on its ability to stimulate growth hormone release.[6] Through the 1990s, both GHB and GBL spread as club drugs and became linked to drug-facilitated sexual assault and fatalities.[7] The US Congress responded in 2000 by scheduling GHB and designating GBL a List I chemical.[7][8]
Contemporary landscape
GBL use increased after GHB's scheduling — its industrial availability made it a ready substitute, with US production estimated at 185,000 metric tons per year.[2] The UK classified GBL as Class B in 2009 following its first confirmed fatality;[9] France banned public sale in 2011.[4] Today GBL remains a primary chemsex drug in MSM communities across Europe and Australia,[3][10] with ongoing reports of fatalities, severe withdrawal, and complications including kidney failure.[11]
"G" refers interchangeably to GBL, GHB, and 1,4-butanediol in chemsex contexts — a conflation that carries real risk, as their dosing profiles and onset times differ significantly. The name "liquid ecstasy" is misleading: GBL's pharmacology has no relationship to MDMA. GBL's industrial ubiquity — sold as wheel cleaner, paint stripper, and nail polish remover — has made it one of the most accessible controlled-substance precursors globally, with vendors historically using "not for human consumption" labels to skirt regulations.
Chemistry[edit]
Chemistry
Structure
GBL (oxolan-2-one) belongs to the lactone family — cyclic esters that form when a molecule closes into a ring. It is a five-membered ring with one oxygen atom and a carbonyl group, chemically stable under neutral conditions and without stereocenters.[12]
| Molecular formula | C₄H₆O₂ |
| Molecular weight | 86.09 g/mol |
Prodrug relationship
GBL has no receptor activity of its own. Blood enzymes convert it to GHB within approximately one minute of ingestion[13][14] — every pharmacological effect is GHB's. 1,4-butanediol reaches GHB by a slower, liver-mediated pathway. GBL's greater lipophilicity compared to GHB's sodium salt accounts for its faster absorption and brain penetration.[15]
Pharmacology[edit]
Pharmacology
Mechanism of action
GBL has no receptor activity of its own. Blood enzymes convert it to GHB within about one minute,[13][14] and every effect is produced by GHB — confirmed by the complete absence of response in mice lacking GABA-B receptors.[16][17] GHB activates the brain's major inhibitory pathway, but only at concentrations far above the brain's own natural GHB levels.[18][19]
GHB also activates a specific inhibitory receptor subtype that benzodiazepines cannot reach but barbiturates can.[20][21] This explains why benzodiazepines alone provide incomplete relief during GBL withdrawal.
Pharmacokinetics
GBL absorbs rapidly and bypasses the liver's first-pass processing, delivering higher peak GHB levels than an equivalent oral GHB dose. Plasma GHB peaks 20–60 minutes after ingestion,[13][14] then clears quickly — half-life is 20–60 minutes, with only 1–5% of the dose appearing unchanged in urine.[13] Detection windows are short: approximately 6 hours in blood and 10 hours in urine[14] — which complicates forensic investigation of drug-facilitated assault.
Neuroscience[edit]
Neuroscience
Where it acts
GBL's effects are GHB's effects. GHB activates inhibitory receptors across the brain, reducing neurons' ability to fire and suppressing neurotransmitter release.[16] At recreational doses, this produces a distinctive high-amplitude slow-wave brain pattern distinct from natural sleep.[17]
GHB's reinforcing properties come from the brain's reward circuit. It releases the brake on dopamine neurons by activating inhibitory cells that normally hold them in check, flooding the reward center with dopamine[22] — the same pathway alcohol engages.
Neuroadaptation and withdrawal
Chronic use drives adaptations across multiple neurotransmitter systems.[21] When use stops, inhibitory activity collapses and excitatory activity surges — producing tremor, tachycardia, hallucinations, and seizures,[20] pharmacologically similar to alcohol withdrawal but harder to treat.
Animal models consistently fail to replicate the physical dependence seen in human chronic users, and whether this reflects metabolic differences or a deeper neurobiological divergence is unknown.[23] The role of naturally occurring GHB in the brain — present at concentrations sufficient to engage the newly identified CaMKII-alpha target[19] but far below the threshold for activating inhibitory receptors — has not been determined. No longitudinal studies have characterized the long-term cognitive or structural brain effects of chronic GBL dependence and recovery.[5]
Subjective Effects[edit]
Subjective Effects
GBL hits fast. From baseline to full effect takes minutes — a steep rush of warmth, sociability, and physical pleasure that compresses what alcohol spreads over hours. At lower doses the edges of anxiety and inhibition soften; a fraction more and consciousness can drop without warning.
Within the depressant class, GBL sits closest to GHB, which produces the same effects with a slower onset and slightly more dosing room. Alcohol shares the disinhibition and sedation but operates on different receptors, lacks GBL's empathogenic warmth, and unfolds over a much longer arc.
GHB was first synthesized circa 1960 by Henri Laborit as a GABA structural analog designed to cross the blood-brain barrier.[5] GBL entered recreational use as a GHB substitute after GHB's scheduling in 2000, exploiting industrial availability estimated at 185,000 metric tons per year in the United States alone.[6] It remains a primary chemsex substance in MSM communities across Europe and Australia.[7]
Subjective effects include euphoria, disinhibition, empathogenic warmth, sexual arousal enhancement, and sedation. The experience is steep and compressed — a rapid surge of warm sociability and physical pleasure that tips, with minimal dose increase, into deep unconsciousness. Nausea, dizziness, anterograde amnesia, and motor impairment are common unsought effects.
GBL produces rapid physical dependence — faster than alcohol or benzodiazepines[8] — and possesses one of the narrowest therapeutic windows of any recreational substance. Fractions of a milliliter separate euphoric from dangerous doses, with death occurring primarily via respiratory depression during unconsciousness;[9] compulsive redosing accelerates dependence, and withdrawal is medically serious.[10] No clinical trials study GBL directly; the evidence base rests on GHB research, clinical toxicology case series, and significant gaps in the characterization of long-term neurological effects.[11]
History[edit]
History
Discovery
GBL has been manufactured for decades as an industrial solvent, produced by catalytic dehydrogenation of 1,4-butanediol.[12] Its pharmacological significance is entirely derivative: after ingestion, blood lactonases hydrolyze the compound to GHB within approximately one minute.[3][4] GHB itself was first synthesized circa 1960 by Henri Laborit, who designed it as a GABA structural analog capable of crossing the blood-brain barrier, and it entered European clinical use as an anesthetic adjuvant by 1964.[5]
Recreational emergence and scheduling
During the 1980s, GHB was marketed as an over-the-counter bodybuilding supplement based on its capacity to stimulate growth hormone release.[13] Through the 1990s, both GHB and GBL gained widespread popularity as club drugs and became increasingly implicated in drug-facilitated sexual assault and fatalities, particularly when combined with alcohol.[14] The US Congress responded in 2000 with the Hillory J. Farias Act, placing GHB on Schedule I and designating GBL as a List I chemical.[14][15]
Contemporary landscape
GBL use paradoxically increased after GHB's scheduling, as users substituted the still-industrially-available precursor — US production alone is estimated at 185,000 metric tons per year.[6] The UK classified GBL as Class B in 2009 following its first confirmed GBL fatality,[9] while France banned public sale in 2011.[8] GBL remains a primary chemsex substance in MSM communities across Europe and Australia,[7][16] with case reports documenting ongoing fatalities, severe withdrawal, and complications including kidney failure requiring dialysis.[17]
The name "GBL" circulates alongside "G" and "liquid ecstasy" — though the latter is misleading, as the pharmacology bears no relationship to MDMA. In chemsex contexts, "G" refers interchangeably to GBL, GHB, and 1,4-butanediol, a conflation that carries real risk given their different dosing profiles and onset times. The substance's industrial ubiquity — sold as wheel cleaner, paint stripper, and nail polish remover — has made it one of the most accessible controlled-substance precursors globally, with vendors historically exploiting labeling as "not for human consumption" to circumvent regulations.
Chemistry[edit]
Chemistry
Structure
GBL (oxolan-2-one) belongs to the lactone family — cyclic esters formed by internal ring closure of a hydroxy acid. It is a gamma-lactone: a five-membered ring containing four carbon atoms and one oxygen atom, with a carbonyl group at position 2 forming the ester bond. The ring is planar with minimal strain, conferring chemical stability under neutral conditions. GBL has no stereocenters and is therefore achiral.[12]
As a prodrug, GBL possesses no intrinsic receptor activity. Upon contact with blood lactonases, it is hydrolyzed nearly quantitatively to GHB. This prodrug relationship also extends to 1,4-butanediol, which reaches GHB through a slower, liver-mediated oxidation pathway.
| Molecular formula | C₄H₆O₂ |
| Molecular weight | 86.09 g/mol |
Physical properties
GBL is a colorless, hygroscopic liquid with a faint characteristic odor.[18] It boils at 204°C, freezes at −43.3°C, and has a density of 1.12 g/mL — slightly heavier than water. It is fully miscible with water, ethanol, and most common organic solvents.
GBL is stable at neutral pH but hydrolyzes rapidly under basic conditions, the ring opening to yield gamma-hydroxybutyric acid.[18] This base sensitivity is pharmacologically critical: blood pH (~7.4) combined with lactonase activity drives the rapid conversion that underpins GBL's prodrug mechanism. Its complete water miscibility and high lipophilicity relative to GHB's sodium salt account for its faster absorption and brain penetration.
Pharmacology[edit]
Pharmacology
Mechanism of action
GBL has no receptor activity of its own. After ingestion, blood lactonases convert it to GHB with a half-life of approximately one minute.[3][4] Every subsequent effect is produced by GHB — confirmed by the complete absence of any pharmacological response in mice lacking functional GABA-B receptors.[1][2]
GHB acts primarily as a weak partial agonist at GABA-B receptors, the brain's major inhibitory G-protein-coupled receptor. Recreational effects require GHB concentrations far above natural brain levels — roughly a hundredfold elevation.[19][20] This GABA-B activation produces the defining pharmacological profile: sedation, muscle relaxation, and the characteristic EEG delta-wave pattern that accompanies higher-dose loss of consciousness.[2]
GHB also activates extrasynaptic GABA-A receptors of a specific subtype (alpha-4/delta) that does not respond to benzodiazepines but is activated by barbiturates.[21][22] This distinction is clinically important: it explains why benzodiazepines provide incomplete relief during GBL/GHB withdrawal.
A recently identified high-affinity target — CaMKII-alpha, a kinase central to learning and memory — suggests GHB may also integrate excitatory signaling pathways, adding complexity to a mechanism long assumed to be purely inhibitory.[20]
Pharmacokinetics
GBL is rapidly absorbed from the gut due to its lipophilicity. Unlike oral GHB (a sodium salt), GBL is hydrolyzed in the blood rather than the digestive tract, bypassing the liver's first-pass processing. This produces faster onset and higher peak GHB levels than an equivalent oral GHB dose.
Plasma GHB peaks at 20–60 minutes after GBL ingestion.[3][4] The elimination half-life is short — 20–60 minutes[3][4] — and GHB is broken down in the liver to succinic acid, which enters normal energy metabolism and is ultimately exhaled as CO₂. Only 1–5% of the dose appears unchanged in urine.[3]
Detection windows are extremely short: approximately 6 hours in blood and 10 hours in urine.[4] This narrow window complicates forensic investigation of drug-facilitated sexual assault. A urinary GHB threshold of 10 mg/L is used to distinguish exogenous exposure from the body's natural background levels.[23]
Neuroscience[edit]
Neuroscience
Where it acts
GBL's neuroscience is the neuroscience of GHB at elevated concentrations. GABA-B activation across the brain opens potassium channels and closes calcium channels on neurons, reducing their ability to fire and suppressing neurotransmitter release. At pharmacological doses, this widespread inhibition produces high-amplitude delta waves on EEG — a pattern distinct from natural sleep and from other GABA-B agonists like baclofen.[2][1]
The mesolimbic dopamine system underlies GBL's reinforcing properties. GABA-B activation on inhibitory interneurons in the ventral tegmental area disinhibits dopamine neurons, increasing dopamine release in the nucleus accumbens — the same reward circuit engaged by alcohol and benzodiazepines.[24]
Neuroadaptation and withdrawal
Chronic GBL/GHB use drives adaptations across at least six neurotransmitter systems — GABA, glutamate, dopamine, serotonin, norepinephrine, and acetylcholine — along with changes in neurosteroid and oxytocin signaling.[22] Upon cessation, the combined suppression of GABA function and upregulation of glutamate creates a hyperexcitable brain state manifesting as tremor, rapid heart rate, hallucinations, and seizures — pharmacologically analogous to alcohol withdrawal but complicated by receptor components that benzodiazepines cannot address.[21]
Several puzzles remain unresolved. Animal models consistently fail to replicate the physical dependence observed in human chronic users, and whether this reflects species differences in metabolism or fundamental neurobiological divergence is unknown.[25] The physiological role of naturally occurring GHB in the brain — present at concentrations sufficient to engage the newly identified CaMKII-alpha target[20] but far below the threshold for GABA-B activation — has not been determined. No longitudinal studies have characterized the long-term cognitive or structural brain effects of chronic GBL dependence and recovery.[11]
Subjective Effects[edit]
Subjective Effects
GBL's experiential character is defined by a steep dose-response curve compressed into an unusually short timeframe. The transition from baseline to full effect occurs within minutes — not the gradual build of alcohol — producing a distinctive sense of urgency that colors the experience regardless of dose. At lower doses, disinhibition and empathogenic warmth dominate; at common doses, euphoria, tactile sensitivity, and sexual arousal enhancement emerge; fractionally higher, the experience collapses abruptly into deep sedation or loss of consciousness. Set and setting exert moderate influence — social environments amplify sociability, while solitary use accelerates sedation.
Within the depressant class, GBL occupies a unique position. GHB produces identical effects but with slower onset and marginally wider dosing latitude. Alcohol shares the disinhibition and sedation but operates through different receptor subtypes, produces a longer and less euphoric arc, and lacks GBL's pronounced empathogenic and prosexual character.
Effect Grid
Full cognitive euphoria dominates the experience, with pronounced disinhibition and sociability enhancement. Sexual arousal enhancement and empathogenic warmth — tactile sensitivity, prosocial openness, emotional closeness — reach their peak expression. Music enhancement is frequently reported.
Motor control impairment becomes noticeable as ataxia. Nausea may occur. Memory suppression (anterograde amnesia) is possible even at this range. The compulsive redosing urge typically emerges here, driven by the short duration and desire to sustain euphoria.
Cognitive impairment is moderate. Judgment is meaningfully affected by the combination of disinhibition and analysis suppression. The steep dose-response curve means the upper end of this range borders on strong effects — a difference of 0.5 mL can shift the experience substantially.
Modeled from the effect's dose-dependence curve — not per-substance measurements.
Auditory enhancement · Dreaming enhancement · Proprioceptive distortion · Sleep-transition hallucinations · Visual acuity suppression · Visual processing suppression · Auditory hallucinations · External hallucinations · Internal hallucinations
Visual acuity suppression · Visual processing suppression · Auditory hallucinations · External hallucinations · Internal hallucinations
Dizziness · Bodily heaviness · Breathing alteration · Physical fatigue · Sexual arousal enhancement · Tactile euphoria · Laughter fits · Nausea · Nystagmus (eye wobbles) · Headache · Pain suppression · Spontaneous body sensations · Vomiting · Involuntary body movements · Temperature dysregulation · Sexual arousal suppression · Stimulation · Bodily dissociation
Physical fatigue · Sexual arousal enhancement · Tactile euphoria · Laughter fits · Nausea · Nystagmus (eye wobbles) · Headache · Pain suppression · Spontaneous body sensations · Vomiting · Involuntary body movements · Sexual arousal suppression · Stimulation · Bodily dissociation
Confusion · Focus suppression · Information processing suppression · Memory suppression · Suggestibility enhancement · Thought deceleration · Delusions of sobriety · Cognitive fatigue · Language suppression · Memory fragmentation · Thought disorganization · Humor enhancement · Cognitive dysphoria · Amnesia · Delirium
Memory suppression · Thought deceleration · Delusions of sobriety · Cognitive fatigue · Language suppression · Memory fragmentation · Thought disorganization · Humor enhancement · Cognitive dysphoria · Amnesia · Delirium
Emotional suppression · Anxiety · Dysphoria
Trust enhancement · Communication enhancement · Communication suppression · Emotional susceptibility · Derealization · Cognitive disconnection
Derealization · Cognitive disconnection
Timeline
First awareness of effects: a spreading warmth and mild relaxation. Subtle mood shift detectable within minutes of ingestion.
Rapid escalation to full effects. Euphoria builds quickly, disinhibition and sociability emerge. The speed of this transition is characteristic of GBL.
Maximum intensity — euphoria, disinhibition, empathogenic warmth, and sexual arousal enhancement at common doses; sedation dominates at strong doses. Compulsive redosing urge is strongest here.
Rapid decline in effects. Euphoria and disinhibition fade, replaced by drowsiness. Cognitive function begins returning but residual impairment persists.
Residual sedation and mild fatigue. Possible headache. Cognitive function largely restored but subtle impairment may linger.
Safety[edit]
- Acute toxicity
- High
- Chronic toxicity
- Moderate
- Withdrawal
- Life-threateningfatal risk
- Tolerance buildup
- rapid
- Tolerance reset
- 10.5 days
- Physical
- High
- Psychological
- High
- Compulsive redosing
- High
- Dose escalation
- Moderate
- Cross-tol.
- GHB · 1,4-butanediol
Toxicity
Acute toxicity
GBL produces dose-dependent sedation and can suppress breathing fatally.[4] The estimated lethal dose for a 70 kg person is roughly 3.75 mL of pure liquid[14] — close to the upper recreational range. safety citation needed No antidote exists; treatment is airway protection and mechanical ventilation.[4]
GBL is considered more acutely dangerous than oral GHB. It absorbs faster, leaving less time to intervene, and differences as small as 0.5 mL can shift the outcome from recreational to dangerous.[24]
Cancer and genetic toxicity
IARC classifies GBL as Group 3 — inadequate evidence for cancer risk in humans, with animal data suggesting it is not carcinogenic.[15] Genetic toxicity testing is predominantly negative across multiple test systems.[15]
Psychological Risks
GBL impairs judgment, lowers inhibition, and erases recent memory — a combination that creates vulnerability to exploitation and risky behavior.[4] It is colorless, nearly odorless, and causes rapid sedation with memory loss, making it a documented drug-facilitated sexual assault agent.[7]
The compulsive redosing urge is a distinct risk. Short duration and rapid onset create a powerful reinforcing cycle — one documented user was redosing every 30 minutes.[11] Withdrawal itself causes significant psychiatric disturbance: hallucinations in 63% of documented episodes, along with confusion, delusions, and paranoia.[25] Long-term psychological effects remain poorly characterized.[5]
Tolerance and Dependence
Tolerance develops within days of regular use.[4][26] Physical dependence develops faster than with alcohol or benzodiazepines,[4] and cross-tolerance exists between GBL, GHB, and 1,4-butanediol.[27] The tolerance reset period is approximately 1–2 weeks. citation needed
GBL withdrawal can be fatal. Medical supervision is essential for cessation after regular use. Do not attempt unsupervised withdrawal.
In a review of 57 withdrawal episodes, the most common features were tremor (67%), hallucinations (63%), rapid heart rate (63%), insomnia (58%), anxiety, agitation, high blood pressure, sweating, confusion, and disorientation; seizures and muscle breakdown each occurred in 7%.[25] Onset is typically 6–24 hours after the last dose,[28][4] and duration ranges from days to three weeks in severe cases.
Benzodiazepines are first-line treatment but provide incomplete relief.[4][20] Barbiturates and pharmaceutical GHB tapering address GBL's specific receptor targets more directly,[20][21] baclofen shows promise as an add-on,[29] and severe presentations warrant intensive care.[11]
Drug Interactions
GBL's interactions share one mechanism: combining it with any other CNS depressant compounds the risk of breathing stopping.[4] Alcohol worsens clinical outcomes even at moderate amounts.[30][31] Opioids — every member of the class — produce lethal synergistic respiratory depression.[4][14] Ketamine and other dissociatives carry the same lethal classification.[4]
Stimulants — MDMA, amphetamine, cocaine, methamphetamine — mask GBL's sedating effects, hiding how intoxicated a person actually is. When the stimulant wears off, sudden collapse can follow.[3] Benzodiazepines, antipsychotics, and sedating antihistamines all compound sedation and respiratory depression. Baclofen at recreational doses poses lethal risk; it is used medically for withdrawal management only under supervision.[29]
Contraindications
9 knownAbsolute contraindications:
- Concurrent alcohol use — synergistic respiratory depression; lethal combination[30][4]
- Concurrent opioid use (any) — synergistic respiratory depression; lethal combination[4]
- Concurrent ketamine or other dissociative use — synergistic depression[4]
- Concurrent use of any sedating medication — including benzodiazepines, barbiturates, sedating antihistamines, antipsychotics, muscle relaxants, and prescription sleep aids
Relative contraindications:
- Respiratory conditions (asthma, COPD, sleep apnea) — GBL produces dose-dependent respiratory depression; impaired baseline breathing increases vulnerability
- Heart rhythm disorders — GBL/GHB can cause slow heart rate at active doses; underlying conduction problems may worsen this
- History of seizures — withdrawal produces seizures in ~7% of cases[25]
- History of substance dependence — GBL's rapid onset, short duration, and compulsive redosing create high reinforcement; prior dependence elevates risk
- Pregnancy and breastfeeding — no human safety data exist safety citation needed
Harm Reduction[edit]
Forms & Identification
GBL circulates as a colorless liquid with a faint solvent-like odor — easily mistaken for water. It is sold industrially as wheel cleaner, paint stripper, and solvent; purity varies, and industrial products may contain manufacturing impurities not intended for human exposure. Standard reagent tests do not reliably identify or quantify it.
The critical practical concern is measurement. GBL is dosed in fractions of a milliliter, and less than 0.5 mL can separate a recreational dose from a dangerous one. Oral syringes marked in 0.1 mL increments are the only appropriate measuring tool — not teaspoons, eyeballed capfuls, or unmarked pipettes.
Guidelines
- Always measure with an oral syringe marked in 0.1 mL increments. Never estimate, pour from the bottle, or use bottle caps.
- Start with a threshold dose and wait at least 90 minutes before considering redosing. Onset varies and full effects may arrive later than expected — "I don't feel it yet" is a dangerous impulse.
- Set a strict redosing limit beforehand. The short duration creates a powerful compulsive redosing urge; each successive dose compounds risk. A timer or trusted companion can enforce the limit.
- Never use alone. GBL can produce sudden unconsciousness. A sober companion who knows what has been taken, when, and how much is the most effective safety measure.
- Eat a light meal 1–2 hours beforehand. Food slows absorption and moderates peak intensity. Never use on a completely empty stomach.
- Avoid all other depressants — alcohol, opioids, benzodiazepines, ketamine, antihistamines, sleep medications. Even small amounts of alcohol dramatically increase risk.
- Keep the container clearly labeled and stored away from drinks. GBL is colorless and water-miscible; accidental ingestion by others is a documented cause of harm.
Aftercare & Integration
Hydration and light nutrition support recovery after GBL use. Most acute effects resolve within two hours, but fatigue, mild confusion, and mood dip can persist for several hours.
Honest self-monitoring for escalating use is the most important aftercare step. The reinforcement cycle can shift from occasional use to around-the-clock dosing within days. Increasing dosing frequency, or anxiety about running out of supply, are early warning signs of developing dependence.
Recovery & Support
GBL dependence requires medical management — unsupervised withdrawal carries serious risk of seizures, psychiatric disturbance, and death. Anyone using GBL daily or near-daily should seek medical advice before stopping.
Treatment options include medically supervised tapering, inpatient detoxification with benzodiazepines or barbiturates, and ongoing support for psychological dependence. Peer support communities familiar with GHB/GBL-specific challenges exist in many countries, particularly within chemsex harm reduction organizations in Europe and Australia.
Recovery resources, crisis lines, and support pathways → View all
Emergency Response
Recognizing an emergency:
- Unconsciousness with inability to be roused by voice or firm shoulder pressure
- Slow, shallow, or irregular breathing (fewer than 10 breaths per minute)
- Blue or grey lips and fingertips
- Vomiting while unconscious or semi-conscious
- Seizure activity
Immediate steps:
- 1. Call emergency services immediately if the person cannot be woken or is breathing abnormally.
- 2. Place the person in the recovery position (on their side, mouth pointing downward) to prevent choking on vomit.
- 3. Stay with them. Monitor breathing continuously.
- 4. Do NOT induce vomiting — GBL is absorbed too rapidly for this to help, and vomiting while unconscious risks fatal aspiration.
- 5. Do NOT give them food or water.
- 6. Do NOT leave an unconscious person "to sleep it off." GBL-induced unconsciousness is not sleep — respiratory arrest can occur.
What to tell the dispatcher: Substance taken (GBL or "G"), amount if known, time of ingestion, current symptoms, and whether any other substances were involved. Good Samaritan laws in many jurisdictions protect people who call for help during a drug emergency.
Reversal agents: None exist. Treatment is entirely supportive — airway protection and ventilation.
Legal Status[edit]
Legal Status
GBL occupies an unusual legal position: it is a high-volume industrial chemical with no international treaty controls, yet it converts directly to a scheduled substance in the body, and most countries that regulate it do so through domestic law alone.
| Jurisdiction | Classification | Key provisions |
|---|---|---|
| United States | List I Chemical (Controlled Substances Act) | Designated List I since 2000.[8] If intended for human consumption, prosecutable as a Schedule I analog under the Federal Analogue Act. Mixtures containing 70% or less GBL may be exempt. Specific penalties under the Hillory J. Farias Act for drug-facilitated sexual assault.[7] |
| United Kingdom | Class B (Misuse of Drugs Act 1971) | Controlled since December 2009 following the first UK GBL fatality.[9] Since June 2022, industrial users no longer require a controlled drugs licence; Class B status for human consumption is maintained.[32] GHB remains Class C. |
| Australia | Schedule 10 (prohibited substance) | Non-polymerized GBL in preparations for domestic and cosmetic use is prohibited. Criminal penalties in all states and territories. |
| Canada | Schedule VI (CDSA) | Import and export prohibited. Indictable offence carries up to 10 years; summary conviction up to 18 months. |
| France | Banned for public sale/transfer | Sale and transfer to the public banned since 2011.[4] |
| Germany | Not listed in narcotics law | Distribution controlled under the Medicines Act if intended for human consumption. Possession not inherently illegal but may be prosecuted on evidence of intent. |
| International | Not scheduled under any UN treaty | Subject to voluntary EU monitoring as a drug precursor. Regulatory approaches vary widely among member states. |
Prodrug considerations
In the United States, the Federal Analogue Act allows prosecution as a Schedule I analog when intent for human consumption can be demonstrated. A 70% concentration exemption has been exploited by vendors marketing GBL as industrial solvent at sub-threshold concentrations. In much of the EU and parts of Asia and South America, GBL remains legally purchasable as an industrial chemical — its complete conversion to a scheduled substance makes it one of the most significant regulatory gaps in global drug policy.
Legal status varies by jurisdiction and changes over time. This information is not legal advice.
Safety[edit]
- Acute toxicity
- High
- Chronic toxicity
- Moderate
- Withdrawal
- Life-threateningfatal risk
- Tolerance buildup
- rapid
- Tolerance reset
- 10.5 days
- Physical
- High
- Psychological
- High
- Compulsive redosing
- High
- Dose escalation
- Moderate
- Cross-tol.
- GHB · 1,4-butanediol
Toxicity
Acute toxicity
GBL produces dose-dependent sedation and respiratory depression that can be fatal.[8] The estimated lethal dose in humans is approximately 60 mg/kg[4] — for a 70 kg person, roughly 3.75 mL of pure liquid, a volume disturbingly close to the upper recreational range. safety citation needed
Plasma GHB around 100 mg/L produces euphoria; around 500 mg/L produces potentially fatal cardiorespiratory collapse.[3] The first confirmed UK fatality involved a 25-year-old male who died from vomit inhalation during GBL-induced unconsciousness.[9] Two additional GBL deaths — one suicide, one accidental — have been documented with full tissue analysis.[26]
No antidote exists. Emergency treatment is purely supportive: airway protection, mechanical ventilation for respiratory failure, and heart monitoring. Stomach pumping is unlikely to help given GBL's near-instant absorption.[8]
GBL is widely considered more acutely dangerous than oral GHB: absorption is faster (less time to intervene), dosing errors are more likely in a pure liquid dosed in fractions of a milliliter, and differences as small as 0.5 mL can shift the outcome from recreational to dangerous.[27]
Cancer and genetic toxicity
IARC classifies GBL as Group 3 — inadequate evidence for cancer risk in humans, with animal data suggesting it is not carcinogenic.[18] Genetic toxicity testing is predominantly negative across multiple test systems.[18]
Psychological Risks
Acute psychological risks include impaired judgment, disinhibition, and anterograde amnesia — a combination that creates vulnerability to exploitation and risky behavior.[8] GBL's role in drug-facilitated sexual assault is well-documented: it is colorless, nearly odorless, and produces rapid sedation with memory loss.[14]
The compulsive redosing urge is a distinct risk. The short duration combined with rapid onset creates a reinforcement cycle — in one documented case, a user was redosing every 30 minutes.[17] This pattern rapidly escalates to physical dependence.
Withdrawal produces significant psychiatric disturbance: hallucinations (auditory and visual) in 63% of documented episodes, along with confusion, disorientation, delusions, and paranoia.[10] One case report described bizarre psychiatric symptoms with recovery not occurring until day 11.[25] Long-term psychological effects of chronic GBL dependence remain poorly characterized.[11]
Tolerance and Dependence
Tolerance develops rapidly — within days of regular use.[8][28] Cross-tolerance exists between GBL, GHB, and 1,4-butanediol.[29] The tolerance reset period is approximately 1–2 weeks. citation needed
Physical dependence develops faster than with alcohol or benzodiazepines.[8] The neurobiological basis involves adaptations across GABA, glutamate, dopamine, serotonin, norepinephrine, and cholinergic systems.[22]
GBL withdrawal can be fatal. Medical supervision is essential for cessation after regular use. Do not attempt unsupervised withdrawal.
In a systematic review of 57 withdrawal episodes, the most common features were: tremor (67%), hallucinations (63%), rapid heart rate (63%), insomnia (58%), anxiety, agitation, high blood pressure, sweating, confusion, and disorientation. Seizures occurred in 7% and muscle breakdown in 7%.[10] Onset is typically 6–24 hours after the last dose.[30][8] Duration ranges from days to three weeks in severe cases. Death has been reported.
Treatment is challenging. Benzodiazepines are first-line[8] but provide incomplete relief, likely because GBL's primary receptor targets are not addressed by benzodiazepines.[21] Barbiturates are alternatives, as they activate the same receptor subtypes engaged by GHB.[21] Baclofen is a promising add-on treatment.[31] Pharmaceutical GHB tapering directly replaces the substance.[22] Intensive care admission is warranted for severe presentations.[17]
Drug Interactions
GBL's interactions are overwhelmingly pharmacodynamic — synergistic depression of the central nervous system — rather than metabolic.[8]
The most dangerous combination is GBL with alcohol. Alcohol co-ingestion significantly worsens clinical outcomes,[32] and synergistic respiratory depression has been confirmed in human studies.[33] Even moderate alcohol intake markedly elevates risk.
All opioids produce lethal synergistic respiratory depression when combined with GBL.[8][4] This applies across the entire opioid class — heroin, morphine, oxycodone, fentanyl, methadone, codeine, tramadol, and all analogs.
Ketamine and other dissociatives produce additive to synergistic depression; the combination is classified as lethal.[8]
Baclofen co-use at recreational doses produces excessive GABA-B activation with lethal risk. However, baclofen is also used therapeutically for withdrawal under medical supervision[31] — the lethal classification applies to uncontrolled use, not medically supervised tapering.
Stimulants (MDMA, amphetamine, cocaine, methamphetamine) carry a distinct risk: they mask GBL's sedating effects, preventing the user from perceiving intoxication depth. When the stimulant wears off, sudden collapse can occur — a pattern frequently observed in chemsex settings.[7]
Benzodiazepines markedly enhance sedation and respiratory depression, with loss of protective airway reflexes. Antipsychotics and sedating antihistamines similarly augment depression.
Contraindications
9 knownAbsolute contraindications:
- Concurrent alcohol use — synergistic respiratory depression; lethal combination[32][8]
- Concurrent opioid use (any) — synergistic respiratory depression; lethal combination[8]
- Concurrent ketamine or other dissociative use — synergistic depression[8]
- Concurrent use of any sedating medication — including benzodiazepines, barbiturates, sedating antihistamines, antipsychotics, muscle relaxants, and prescription sleep aids
Relative contraindications:
- Respiratory conditions (asthma, COPD, sleep apnea) — GBL produces dose-dependent respiratory depression; impaired baseline breathing increases vulnerability
- Heart rhythm disorders — GBL/GHB can cause slow heart rate at active doses; underlying conduction problems may worsen this
- History of seizures — the relationship is complex: GHB has both seizure-suppressing and seizure-promoting properties depending on context; withdrawal produces seizures in ~7% of cases[10]
- History of substance dependence — GBL's rapid onset, short duration, and compulsive redosing create high reinforcement; prior dependence elevates risk
- Pregnancy and breastfeeding — no human safety data exist safety citation needed
Harm Reduction[edit]
Forms & Identification
GBL circulates as a pure, colorless liquid with a faint solvent-like odor — easily confused with water at a glance. Because it is sold industrially as wheel cleaner, paint stripper, and solvent, purity varies between sources, and industrial-grade products may contain manufacturing impurities not intended for human exposure. Standard reagent tests designed for other substances do not reliably identify or quantify GBL; confirming identity typically requires specialized analysis.
The critical practical concern is volumetric precision. GBL is dosed in fractions of a milliliter, and the difference between a recreational and dangerous dose can be less than 0.5 mL. Oral syringes marked in 0.1 mL increments — not teaspoons, eyeballed capfuls, or unmarked pipettes — are the only appropriate measuring tool.
Guidelines
- Always measure with an oral syringe marked in 0.1 mL increments. Never estimate, pour from the bottle, or use bottle caps.
- Start with a threshold dose and wait at least 90 minutes before considering whether to redose. GBL's compressed timeline makes "I don't feel it yet" a dangerous impulse — onset varies but full effects may take longer than expected.
- Set a strict redosing limit beforehand. The short duration creates a powerful compulsive redosing urge; each successive dose compounds risk. A timer or trusted companion can enforce the limit.
- Never use alone. GBL can produce sudden loss of consciousness. A sober companion who knows what has been taken, when, and how much is the single most effective safety measure.
- Eat a light meal 1–2 hours beforehand. Food slows absorption and moderates peak intensity. Never use on a completely empty stomach.
- Avoid all other depressants — alcohol, opioids, benzodiazepines, ketamine, antihistamines, sleep medications. Even small amounts of alcohol dramatically increase risk.
- Keep the container clearly labeled and stored away from drinks. GBL is colorless and water-miscible; accidental ingestion by others is a documented cause of harm.
Aftercare & Integration
After GBL use, hydration and light nutrition support recovery. The short duration means most acute effects resolve within two hours, but fatigue, mild confusion, and mood dip can persist for several hours afterward.
The most important aftercare consideration is honest self-monitoring for escalating use patterns. GBL's rapid onset and short duration produce a reinforcement cycle that can shift from occasional use to around-the-clock dosing within days. If dosing frequency is increasing, or if the thought of not having a supply produces anxiety, these are early warning signs of developing dependence.
Recovery & Support
GBL dependence requires medical management — unsupervised withdrawal carries serious risk including seizures, psychiatric disturbance, and death. Anyone using GBL daily or near-daily should seek medical advice before stopping.
Treatment options include medically supervised tapering (using pharmaceutical GHB or baclofen under clinical oversight), inpatient detoxification with benzodiazepines or barbiturates, and ongoing support for psychological dependence. Peer support communities familiar with GHB/GBL-specific challenges exist in many countries, particularly within chemsex harm reduction organizations in Europe and Australia.
Recovery resources, crisis lines, and support pathways → View all
Emergency Response
Recognizing an emergency:
- Unconsciousness with inability to be roused by voice or firm shoulder pressure
- Slow, shallow, or irregular breathing (fewer than 10 breaths per minute)
- Blue or grey lips and fingertips
- Vomiting while unconscious or semi-conscious
- Seizure activity
Immediate steps:
- 1. Call emergency services immediately if the person cannot be woken or is breathing abnormally.
- 2. Place the person in the recovery position (on their side, mouth pointing downward) to prevent choking on vomit.
- 3. Stay with them. Monitor breathing continuously.
- 4. Do NOT induce vomiting — GBL is absorbed too rapidly for this to help, and vomiting while unconscious risks fatal aspiration.
- 5. Do NOT give them food or water.
- 6. Do NOT leave an unconscious person "to sleep it off." GBL-induced unconsciousness is not sleep — respiratory arrest can occur.
What to tell the dispatcher: Substance taken (GBL or "G"), amount if known, time of ingestion, current symptoms, and whether any other substances were involved. Good Samaritan laws in many jurisdictions protect people who call for help during a drug emergency.
Reversal agents: None exist. Treatment is entirely supportive — airway protection and ventilation.
Legal Status[edit]
Legal Status
GBL occupies an unusual regulatory position. Unlike GHB, which has been scheduled under the UN Convention on Psychotropic Substances (Schedule IV) since 2001, GBL is not controlled under any international treaty. Its dual identity — high-volume industrial chemical and potent psychoactive prodrug — creates persistent regulatory tension. Most jurisdictions that control GBL do so through domestic legislation, and many countries have no specific GBL controls at all.
| Jurisdiction | Classification | Key provisions |
|---|---|---|
| United States | List I Chemical (Controlled Substances Act) | Designated List I since 2000.[15] If intended for human consumption, prosecutable as a Schedule I analog under the Federal Analogue Act. Mixtures containing 70% or less GBL may be exempt. Specific penalties under the Hillory J. Farias Act for drug-facilitated sexual assault.[14] |
| United Kingdom | Class B (Misuse of Drugs Act 1971) | Controlled since December 2009 following the first UK GBL fatality.[9] Since June 2022, industrial users no longer require a controlled drugs licence; Class B status for human consumption is maintained.[34] GHB remains Class C. |
| Australia | Schedule 10 (prohibited substance) | Non-polymerized GBL in preparations for domestic and cosmetic use is prohibited. Criminal penalties in all states and territories. |
| Canada | Schedule VI (CDSA) | Import and export prohibited. Indictable offence carries up to 10 years; summary conviction up to 18 months. |
| France | Banned for public sale/transfer | Sale and transfer to the public banned since 2011.[8] |
| Germany | Not listed in narcotics law | Distribution controlled under the Medicines Act if intended for human consumption. Possession not inherently illegal but may be prosecuted on evidence of intent. |
| International | Not scheduled under any UN treaty | Subject to voluntary EU monitoring as a drug precursor. Regulatory approaches vary widely among member states. |
Prodrug considerations
GBL's legal status is complicated by its prodrug relationship with GHB. In the United States, the Federal Analogue Act permits prosecution as a Schedule I analog when evidence demonstrates intent for human consumption — a lower threshold than full scheduling but one requiring proof of intent. The 70% concentration exemption for GBL-containing mixtures has been exploited by vendors marketing GBL as "industrial solvent" at concentrations below the threshold.
In jurisdictions without specific GBL controls — much of the EU, parts of Asia and South America — GBL remains legally purchasable as an industrial chemical. This accessibility, combined with its rapid and complete conversion to a scheduled substance, makes GBL one of the most significant regulatory gaps in global drug policy.
Frequently asked questions
What is GBL?
GBL is a cyclic lactone prodrug rapidly hydrolyzed to gamma-hydroxybutyric acid (GHB) in the bloodstream, classified as a depressant. It acts primarily through GABA-B receptor agonism, producing rapid-onset, short-duration effects with a notably narrow therapeutic window.
How long does GBL last?
Total duration by route of administration — Oral: 1 – 2 hours. Ranges vary with dose and individual factors; see the duration table for onset, peak, and after-effect phases.
Where can I find dosage information for GBL?
Psychedex publishes a dosage table for GBL on this page covering these routes of administration: oral. Dose values are presented only in that table, always alongside their route of administration.
What are dangerous combinations with GBL?
The highest-severity documented interactions for GBL: GHB, GBL (Lethal), Ketamine, DXM, PCP (Lethal), Opioids (Lethal), Alpha-2 adrenergic receptor antagonist (Dangerous), Amphetamines (Dangerous). See the interactions section for the full list with mechanisms and severity levels.
Is GBL addictive?
Psychedex records tolerance and dependence data rather than a yes/no rating. Recorded tolerance indicators for GBL: tolerance builds rapid; full reset takes 10.5 days; cross-tolerance develops with GHB, 1,4-butanediol. See the article's dependence and safety sections for recorded dependence data.
experience reports
No experience reports yet. Be the first to contribute.
First-person accounts of subjective effects, timing, and outcomes — submitted for harm reduction.
references
- [1]
- [2]
- [3] ^abcGiorgetti R, Tagliabracci A, Schifano F, Zaami S, Marinelli E (2017) When Chems Meet Sex: A Rising Phenomenon Called ChemSex — Current Neuropharmacology doi:10.2174/1570159x15666161117151148
- [4]
- [5] ^abcHenderson DL, Ginsberg JP (2008) Withdrawal, recovery, and long-term sequelae of gamma-butyrolactone dependence: a case report — The American Journal on Addictions doi:10.1080/10550490802266193
- [6] ^Van Cauter E, Plat L, Scharf MB, et al. (1997) Simultaneous stimulation of slow-wave sleep and growth hormone secretion by gamma-hydroxybutyrate in normal young men — Journal of Clinical Investigation doi:10.1172/jci119587
references
- [1] ^abcKaupmann K, Cryan JF, Wellendorph P, et al. (2003) Specific gamma-hydroxybutyrate-binding sites but loss of pharmacological effects of gamma-hydroxybutyrate in GABA(B)(1)-deficient mice — European Journal of Neuroscience PMID:14656321
- [2] ^abcdVienne J, Bettler B, Franken P, Tafti M (2010) Differential Effects of GABA-B Receptor Subtypes, γ-Hydroxybutyric Acid, and Baclofen on EEG Activity and Sleep Regulation — Journal of Neuroscience doi:10.1523/jneurosci.3145-10.2010
- [3]
- [4]
- [5]
- [6]