1,3-Butanediol
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1,3-Butanediol (butane-1,3-diol) is a synthetic depressant of the aliphatic diol class. It is a positional isomer of 1,4-butanediol, distinguished by producing ketone bodies rather than GHB. 1,3-Butanediol is a prodrug for β-hydroxybutyrate, producing its effects through hepatic metabolic conversion rather than direct receptor engagement.[1]
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Pharmacological interest emerged in 1976 when Majchrowicz et al. demonstrated the compound's capacity to suppress ethanol withdrawal in rats.[2] DARPA-funded ketone ester research later incorporated it as a diol backbone for military performance and therapeutic applications.[3] Since approximately 2019, (R)-1,3-butanediol has been commercially marketed as a recreational alcohol alternative in the emerging "sober curious" marketplace.
Subjective effects include disinhibition, anxiolysis, euphoria, dizziness, and sedation. The experience resembles ethanol intoxication — relaxation and social ease without the stimulatory onset characteristic of alcohol — compressed into roughly half ethanol's duration.[4][5] Gastrointestinal distress is the most common unsought effect and is dose-limiting.
Animal studies demonstrate physical dependence with withdrawal seizure susceptibility and bidirectional cross-tolerance with ethanol;[4] human dependence has not been assessed. Acute toxicity is low — approximately 2.5-fold less lethal than ethanol in animals[6] — but blood sugar reduction is a documented risk at higher doses.[7] No controlled human intoxication studies, overdose case reports, or drug interaction data exist — substantial gaps given expanding commercial availability.
History[edit]
Discovery
1,3-Butanediol (CAS 107-88-0) has been commercially available as an industrial solvent, humectant, and plasticizer since at least the mid-20th century.[8] The first controlled human metabolic study, published by Tobin et al. in 1975, established 1,3-BD as a nontoxic caloric substrate that lowered blood glucose and spared nitrogen — opening investigation of the compound as an alternative energy source and food ingredient.[7]
Pharmacological investigation
The compound's psychoactive properties were first characterized in 1976 when Majchrowicz, Hunt, and Piantadosi published in Science that oral 1,3-BD suppressed ethanol withdrawal in rats, establishing both CNS depressant activity and cross-tolerance with alcohol.[2] Frye et al. at the University of North Carolina conducted the most comprehensive neuropharmacological comparison in 1981, finding 1,3-BD approximately equipotent to ethanol behaviorally despite lower brain concentrations — and documenting physical dependence with withdrawal-induced CNS hyperexcitability.[4] A 1983 follow-up demonstrated that direct brain injection of 1,3-BD was inactive, confirming that its CNS effects require peripheral metabolic conversion.[1]
Commercial emergence
Richard Veech at the National Institutes of Health pursued ketone body esters as therapeutic agents from approximately the 2000s, incorporating 1,3-butanediol as the diol backbone in formulations funded partly by DARPA for soldier endurance research.[3] From approximately 2019, (R)-1,3-butanediol appeared in commercially marketed "alcohol alternative" beverages, including KetoneAid Hard Ketones and Avela™. As of 2026, multiple companies market these products as social intoxicants with claimed reduced hangover risk, though the compound's recreational pharmacology has yet to be formally characterized in controlled human studies.
The name "1,3-butanediol" derives from its four-carbon (butane) backbone bearing two hydroxyl groups (diol) at the 1- and 3-positions. The abbreviation 1,3-BD is standard in pharmacological literature; commercial products typically use the enantiomer designation (R)-1,3-butanediol or the brand term "Hard Ketones." The compound occupies an unusual cultural niche — marketed simultaneously to biohackers and ketogenic dieters as a metabolic supplement and to social drinkers as a legal alcohol replacement.
Chemistry[edit]
Structural class
1,3-Butanediol belongs to the aliphatic diol family — organic compounds bearing two hydroxyl groups on a saturated carbon chain. Its IUPAC name is butane-1,3-diol. The compound is a structural isomer of 1,4-butanediol, with hydroxyl groups at the 1- and 3-positions rather than the 1- and 4-positions. This positional difference is pharmacologically decisive: 1,4-BD converts to γ-hydroxybutyrate (GHB) and is scheduled in multiple jurisdictions, whereas 1,3-BD converts to β-hydroxybutyrate (BHB) and remains unscheduled.[4]
Molecular properties
| Molecular formula | C₄H₁₀O₂ |
| Molecular weight | 90.12 g/mol |
The molecule consists of a four-carbon saturated chain with a primary alcohol at C-1 and a secondary alcohol at C-3. No ring systems, aromatic groups, or nitrogen atoms are present.[9]
Stereochemistry
1,3-Butanediol has one chirality center at C-3, giving rise to two enantiomers: (R)-1,3-butanediol and (S)-1,3-butanediol. The racemic mixture is the standard industrial form. The (R)-enantiomer is considered more pharmacologically active and is the form marketed in current commercial products (Avela™, KetoneAid), though controlled head-to-head human comparisons are limited.[10][5]
Physical properties
1,3-Butanediol is a clear, colorless to faintly yellow viscous liquid with a bitter-sweet taste. It is fully miscible with water, facilitating oral administration in aqueous beverage formulations. The boiling point (203–204 °C) and flash point (121 °C) indicate low volatility and minimal inhalation risk under ambient conditions.[9]
Pharmacology[edit]
Mechanism of action
1,3-Butanediol functions as a prodrug for (R)-β-hydroxybutyrate (BHB), the body's principal ketone. After oral ingestion, alcohol dehydrogenase in the liver converts 1,3-BD to an intermediate aldehyde, which aldehyde dehydrogenase then converts to BHB.[6]
BHB is the primary active metabolite. It exerts downstream effects through several pathways: activation of the anti-inflammatory receptor HCAR2, inhibition of the NLRP3 inflammasome, and epigenetic modification via histone deacetylase inhibition.[11]
The compound does not directly activate GABA receptors in the brain. When microinjected into brain tissue, 1,3-BD produces no effect — while GABA-targeting drugs remain active at the same site.[1] This confirms that its CNS depressant effects require peripheral metabolic conversion rather than direct receptor binding.
Classification disputes
Several pharmacological classifications attributed to 1,3-butanediol in reference databases are unverified or incorrect:
- GABA-A positive allosteric modulator — No direct binding data exist. Central GABA receptor sites are not the compound's site of action.[1] This classification is unverified for the parent compound.
- GHB receptor agonist — 1,3-Butanediol does not convert to GHB. This pathway applies to 1,4-butanediol, a different isomer.[4] This classification is very likely incorrect.
- NMDA receptor antagonist — No published evidence supports this classification. Unverified.
Pharmacokinetics
At 34.5 g oral (R)-1,3-BD consumed as three split servings over 60 minutes in fasting adults, blood BHB rose from a baseline of 0.23 mmol/L to a peak of 2.10 mmol/L, reaching maximum concentration approximately 2.25 hours after dosing. A significant sex difference was observed: females showed later peak times and greater total BHB exposure than males.[12]
At lower doses (0.35 g/kg racemic mixture 1,3-BD), blood BHB rose to 0.44–0.79 mmol/L during exercise and peaked at 1.38 mmol/L post-exercise.[13] Elevated ketone levels persist for approximately 1–2 hours after moderate single doses[14] and up to five hours with split-dose protocols.[12]
Metabolism is primarily hepatic. The psychoactive effects are likely biphasic: an early phase of direct alcohol-like CNS action from the parent compound crossing the blood-brain barrier, followed by a longer phase mediated by circulating BHB. The relative contributions of these phases to the subjective experience remain uncharacterized.
Neuroscience[edit]
Where it acts
1,3-Butanediol produces CNS depression through a mechanism that is incompletely understood but demonstrably distinct from direct GABAergic action.[1] In rats, the compound impairs motor coordination, reduces anxiety-like behavior, lowers blood pressure, and decreases cerebellar cGMP — a profile that parallels ethanol but occurs at lower brain concentrations, suggesting either greater intrinsic potency or more efficient conversion to active metabolites within the brain.[4]
Why it matters
The most explanatory framework for 1,3-BD's brain effects is metabolic competition. BHB serves as an alternative brain fuel, partially displacing glucose oxidation. This fuel-switching may alter neurotransmitter synthesis, synaptic energy availability, and neuronal excitability — and explains the paradoxical finding that ketone supplementation dampens rather than enhances alcohol's effects.[15][16]
Gueldry and Bralet demonstrated that 1,3-BD produces distinctive brain metabolic changes — reduced glycolytic rate, decreased lactate, increased glucose and glycogen stores — that were not replicated by equivalent BHB infusion alone.[17] This suggests the parent compound may have independent central effects beyond its role as a BHB precursor.
Several fundamental questions remain unresolved. No receptor binding characterization has been performed for 1,3-BD, leaving the molecular target of its direct CNS depression unknown. Whether BHB generated within the brain contributes meaningfully to psychoactive effects — as distinct from BHB arriving via circulation — is uncertain.[17]
Subjective Effects[edit]
The 1,3-butanediol experience is shaped by its prodrug pharmacology: a composite of direct alcohol-like sedation from the parent compound and a secondary metabolic phase driven by rising BHB levels. Split dosing over 30–60 minutes shifts the balance toward the BHB phase and reduces gastrointestinal distress, while rapid bolus dosing intensifies the acute intoxicant component. Food intake substantially modulates both onset and tolerability — fasted administration produces faster, more pronounced effects.
Compared to ethanol, 1,3-butanediol produces a qualitatively similar depressant profile — relaxation, disinhibition, anxiolysis — but lacks the stimulatory phase that characterizes early alcohol intoxication.[4][5] The total experience is notably shorter, making it feel more contained than a comparable evening of drinking.
Effect Grid
At common doses (~0.35–0.5 g/kg oral, approximately 25–35 g for a 70 kg person), the full alcohol-like intoxication profile emerges. Disinhibition, relaxation, and euphoria are clearly present. Anxiety suppression is pronounced. Dizziness becomes noticeable. Thought deceleration and mild analysis suppression are reported at this level.
Gastrointestinal symptoms (nausea, abdominal cramping) are common and dose-limiting, particularly with rapid consumption. Divided dosing over 30–60 minutes substantially reduces GI distress. Consuming with food improves tolerability.
Subjective effects last approximately 2–3 hours, notably shorter than ethanol at equivalent intoxication levels. Motor coordination is impaired. Driving and operation of machinery are unsafe.
Modeled from the effect's dose-dependence curve — not per-substance measurements.
Sleep-transition hallucinations · Visual acuity suppression · Visual haze / noise · Visual processing suppression
Bodily heaviness · Nystagmus (eye wobbles) · Physical fatigue · Dehydration sensation · Dry mouth · Headache · Laughter fits · Nausea · Pain suppression · Tactile euphoria · Appetite suppression · Stimulation · Body schema distortion · Breathing alteration · Increased urination · Sexual arousal enhancement · Vomiting · Bodily dissociation
Dry mouth · Headache · Laughter fits · Nausea · Pain suppression · Tactile euphoria · Appetite suppression · Stimulation · Body schema distortion · Breathing alteration · Increased urination · Sexual arousal enhancement · Vomiting · Bodily dissociation
Cognitive euphoria · Analysis suppression · Thought deceleration · Cognitive fatigue · Language suppression · Compulsive redosing urge · Confusion · Memory fragmentation · Memory suppression · Motivation suppression · Thought disorganization · Humor enhancement · Delusions of sobriety · Amnesia · Delirium
Cognitive fatigue · Language suppression · Confusion · Memory fragmentation · Memory suppression · Motivation suppression · Thought disorganization · Humor enhancement · Delusions of sobriety · Amnesia · Delirium
Sociability enhancement · Communication enhancement · Depersonalization · Derealization · Cognitive disconnection
Cognitive disconnection
Timeline
First perceptible effects emerge as a subtle warmth or mild relaxation. Gastrointestinal awareness may precede psychoactive onset. BHB elevation begins ~30 minutes post-ingestion.
Alcohol-like relaxation builds progressively. Mild disinhibition and mood elevation become noticeable. GI discomfort, if present, typically peaks during this phase.
Maximum subjective intoxication: euphoria, disinhibition, dizziness, and anxiety suppression are most pronounced. Motor coordination is impaired. BHB Cmax occurs approximately 2 hours post-dose.
Effects diminish more rapidly than ethanol at comparable intoxication levels. Residual relaxation and mild cognitive slowing may persist. GI symptoms typically resolve during this phase.
Residual metabolic effects from elevated BHB may include mild fatigue or altered appetite. Hypoglycemia risk persists in susceptible individuals during this window.
⚠ Do not drive or operate machinery until all subjective effects and any residual dizziness have fully resolved, typically several hours after last dose.
Safety[edit]
- Acute toxicity
- Low
- Chronic toxicity
- Moderate
- Withdrawal
- Moderate
- Tolerance buildup
- moderate
- Tolerance reset
- —
- Physical
- Moderate
- Psychological
- Low
- Compulsive redosing
- Low
- Dose escalation
- Moderate
- Cross-tol.
- ethanol
Toxicity
Acute toxicity
Acute toxicity is low. The rat oral LD₅₀ of 18,610 mg/kg is approximately 2.5-fold higher than ethanol's (~7,100 mg/kg).[6][9] The compound holds FDA GRAS (Generally Recognized As Safe) status as a food flavoring agent.[10]
Controlled human studies have documented tolerability at doses up to 40 g/day for 5 days and 15 g/day for 14 days without significant adverse effects.[10] A 28-day trial of a ketone ester formulation at 12.5–25 g/day found no clinically meaningful safety changes.[18] At 34.5 g in a single session, the compound was well tolerated with mild GI symptoms in most participants.[12]
No published acute overdose case reports specific to 1,3-butanediol exist (as distinct from 1,4-butanediol). No data on respiratory depression potential at high doses in humans are available. No human lethal dose has been determined.safety citation needed
Metabolic effects
Low blood sugar is a documented effect at higher doses. Tobin et al. demonstrated blood glucose reduction in humans receiving 1,3-BD as a dietary supplement.[7] Animal studies confirmed this finding at elevated doses.[6]
Dehydration occurred in rats consuming 1,3-BD at 10–20% in drinking water.[6] Metabolic acidosis was observed only at very high doses in animals.[6]
Liver effects
Minor liver changes (sinusoidal dilation) appeared in rats at high chronic doses, but no fatty liver or overt liver damage was noted.[6] Morris et al. noted that 1,3-butanediol "is used in some formulations despite limited safety data" at population level.[19]
Common adverse effects
The most frequently reported adverse effects across published human studies:
- Gastrointestinal distress (nausea, abdominal cramping) — most common, dose-related[13][12]
- Headache — 5 of 26 participants at 34.5 g (2 possibly drug-related)[12]
- Euphoria and dizziness — reported at ≥0.35 g/kg doses[13]
Psychological risks
No published reports of psychological distress, psychosis, or psychiatric destabilization attributable to 1,3-butanediol exist. The subjective effects are alcohol-like in character,[5] and the psychological risk profile is expected to parallel ethanol at comparable intoxication levels: impaired judgment, disinhibition-related risk-taking, and emotional lability.
No cases of persistent perceptual disturbances have been reported, consistent with the compound's depressant (non-psychedelic) classification. The primary psychological risk at intoxicating doses is alcohol-like behavioral disinhibition and decision impairment.
Tolerance & dependence
Frye et al. demonstrated that chronic 1,3-BD administration in rats produced measurable tolerance and physical dependence.[4] Withdrawal after chronic use caused CNS hyperexcitability — the characteristic withdrawal pattern of sedative-hypnotic substances, including tremor and increased seizure susceptibility.
Majchrowicz et al. established bidirectional cross-tolerance between 1,3-BD and ethanol: 1,3-BD suppressed ethanol withdrawal, and ethanol-tolerant animals showed reduced response to 1,3-BD.[2]
Human abuse liability has not been formally assessed. Given demonstrated physical dependence and cross-tolerance with ethanol in animal models, dependence potential in chronic recreational users is plausible but unquantified. No published human withdrawal case reports exist.safety citation needed
The molecular mechanisms underlying tolerance development have not been characterized.
Drug interactions
Ethanol
The interaction with ethanol is pharmacologically complex. Three mechanisms operate simultaneously:
Competitive substrate inhibition: Both compounds compete for alcohol dehydrogenase. Co-administration may slow 1,3-BD's conversion to BHB, prolonging exposure to the parent compound and altering the effect balance.[4][2]
Cross-tolerance: Bidirectional cross-tolerance at the CNS level is established in animal models.[4][2]
Paradoxical dampening: Ketone supplementation dampened both subjective and objective responses to alcohol in healthy volunteers[15] and reduced alcohol craving in individuals with alcohol use disorder.[16]
Other CNS depressants
As a CNS depressant with ethanol-like properties, additive sedation with benzodiazepines, barbiturates, opioids, and GHB/GBL is expected. No 1,3-BD-specific interaction studies with any of these substance classes exist.safety citation needed
Blood sugar-lowering agents
1,3-BD lowers blood glucose in humans.[7] Additive low blood sugar risk with insulin, metformin, and other diabetes medications is plausible. No published interaction studies exist.
Contraindications
Diabetes and blood sugar instability: 1,3-BD produces documented blood glucose reduction in humans.[7] Individuals with diabetes or those taking blood sugar-lowering medications face additive risk.
Concurrent CNS depressant use: Additive sedation risk applies at a class level. No 1,3-BD-specific combination studies have been published.safety citation needed
Pregnancy: One rat study showed no adverse fetal effects at high chronic doses.[20] No human pregnancy data exist. Standard precautionary avoidance applies.
Alcohol use disorder: Ketone supplementation may reduce alcohol sensitivity and craving,[15][16] but competitive enzyme inhibition by ethanol blocks 1,3-BD metabolism. Individuals in active alcohol use may have unpredictable responses due to cross-tolerance and enzyme competition.
Harm Reduction[edit]
Forms & Identification
The critical identification concern with 1,3-butanediol is distinguishing it from its positional isomer 1,4-butanediol, which converts to GHB and is scheduled in multiple jurisdictions. Both are clear, viscous liquids that are difficult to tell apart by appearance or taste alone. Purchasing from established commercial brands (Avela™, KetoneAid) with labeled (R)-1,3-butanediol content largely eliminates this risk.
Bulk liquid sourced from chemical suppliers carries greater uncertainty. If using non-branded product, verify the CAS number (107-88-0 for 1,3-BD vs. 110-63-4 for 1,4-BD) on the certificate of analysis. Standard reagent testing kits do not reliably differentiate the two isomers.
Guidelines
- Start with a low dose and wait at least 90 minutes before redosing — peak BHB levels arrive later than the initial alcohol-like onset
- Split dosing over 30–60 minutes reduces nausea and shifts the experience toward the smoother BHB-mediated phase
- Eat a moderate meal beforehand to reduce gastrointestinal distress
- Stay hydrated throughout the session
- Individuals with diabetes or taking blood sugar-lowering medications should monitor glucose levels, as 1,3-BD lowers blood sugar
- Do not combine with ethanol or other CNS depressants — the interaction is complex and unpredictable
- Keep sessions infrequent — animal studies demonstrate physical dependence with chronic use[4]
Set & Setting
1,3-Butanediol produces alcohol-like intoxication, and the same environmental considerations that apply to drinking apply here. Social settings with trusted companions are preferable to solitary use, particularly when exploring dosing for the first time. Avoid situations requiring motor coordination, driving, or complex decision-making.
Food intake substantially modulates the experience. Fasted administration produces faster onset and more intense effects; eating beforehand smooths the curve and reduces gastrointestinal distress. Hydration matters — the compound can contribute to dehydration, especially at higher doses.
Aftercare & integration. 1,3-Butanediol's shorter duration means the post-experience window is compressed compared to alcohol. Most users report feeling baseline within a few hours. Prioritize hydration and a balanced meal after the session to replenish glucose and fluids.
If gastrointestinal discomfort persists beyond a few hours, rest and bland food are sufficient for most cases. Headache, reported in a minority of users, typically resolves with hydration and standard over-the-counter analgesics. Note your response to specific doses and protocols for future reference — individual variability is significant, and females may experience stronger and longer-lasting effects than males.[12]
Recovery & Support
Animal studies demonstrate that chronic 1,3-BD use produces physical dependence with a withdrawal resembling alcohol withdrawal.[4] Bidirectional cross-tolerance with ethanol is established,[2] meaning individuals with alcohol dependence history may be at heightened risk.
If regular use has developed and stopping produces anxiety, tremor, or sleep disruption, seek medical guidance — sedative-hypnotic withdrawal can be medically serious. Addiction support resources designed for alcohol dependence are the closest available framework. SAMHSA's National Helpline (1-800-662-4357) provides free, confidential treatment referrals.
Recovery resources, crisis lines, and support pathways → View all
Emergency Response
As a CNS depressant, the primary emergency concerns are excessive sedation and possible low blood sugar.
Recognizing an emergency:
- Unresponsiveness or inability to be roused
- Severely slurred speech or loss of motor control beyond typical mild intoxication
- Vomiting while semi-conscious (aspiration risk)
- Signs of low blood sugar: confusion, shakiness, sweating, rapid heartbeat
- Breathing that becomes slow or irregular
Immediate steps:
- Do not leave the person alone
- If conscious and showing signs of low blood sugar, provide a sugary drink or food
- If unconscious, place in the recovery position (on their side) to protect the airway
- Call emergency services if the person cannot be roused, is vomiting while unconscious, or shows breathing changes
- Do not induce vomiting
What to tell the dispatcher: Name the substance (1,3-butanediol), approximate amount consumed, time of ingestion, and current symptoms. Good Samaritan laws in many jurisdictions protect people who call for help during a drug-related emergency.
Legal Status[edit]
As of April 2026, 1,3-butanediol is not a controlled substance in any jurisdiction for which published scheduling data were identified. The compound holds FDA GRAS status in the United States and is commercially available as a food ingredient and functional beverage component in multiple markets.[10] Its positional isomer 1,4-butanediol — which converts to GHB — is scheduled in several jurisdictions; 1,3-BD has not been affected by these scheduling actions.
| Jurisdiction | Classification | Key provisions |
|---|---|---|
| United States | Not scheduled (GRAS food ingredient) | Not controlled under the CSA; FDA GRAS status for food flavoring; commercially available as supplement and beverage[10] |
| United Kingdom | Not controlled | Not listed in Schedules to the Misuse of Drugs Act 1971; 1,4-BD is controlled but 1,3-BD is not |
| European Union | Not scheduled | No EU-level controlled substance classification; available as food ingredient |
| Canada | Not scheduled | Not listed under the Controlled Drugs and Substances Act (CDSA) |
| Australia | Not scheduled | Not listed in SUSMP; 1,4-BD listed as border-controlled drug from March 2024 but 1,3-BD is unaffected |
Regulatory considerations
The compound's current legal status may evolve as recreational commercial products gain wider distribution and regulatory attention increases. Its structural relationship to the controlled substance 1,4-butanediol could attract structural analog act scrutiny in some jurisdictions, though the pharmacological and metabolic profiles of the two isomers are fundamentally distinct.
references
- [1]
- [2]
- [3] ^abVeech RL (2014) Ketone ester effects on metabolism and transcription — Journal of Lipid Research doi:10.1194/jlr.r046292
- [4]
- [5]
- [6]