γ-Butyrolactone is a hygroscopic colorless liquid with a weak characteristic odor.
Soluble in water, GBL is a common solvent and reagent in chemistry as well as being
used as a flavouring, as a cleaning solvent, as a superglue remover, and as a solvent in
some wet aluminium electrolytic capacitors.
In humans it acts as a prodrug for γ-hydroxybutyric acid, and it is used as a recreational intoxicant
with effects similar to alcohol.
Occurrence GBL has been found in extracts from samples
of unadulterated wines.
This finding indicates that GBL is a naturally occurring component in some wines and may
be present in similar products.
The concentration detected was approximately 5 μg/mL and was easily observed using a simple
extraction technique followed by GC/MS analysis.
GBL can be found in cheese flavourings but typically results in a content of 0.0002%
GBL in the final foodstuff.
Preparation GBL is produced industrially by dehydrogenation
of 1,4-butanediol.
This route proceeds via dehydration of GHB.
In the laboratory, it may also be obtained via the oxidation of tetrahydrofuran, for
example with aqueous sodium bromate.
Reactions As a lactone, GBL is hydrolyzed under basic
conditions, for example in a sodium hydroxide solution into sodium gamma-hydroxybutyrate,
the sodium salt of gamma-hydroxybutyric acid.
In acidic water, a mixture of the lactone and acid forms coexist in an equilibrium.
These compounds then may go on to form a polymer.
When treated with a non-nucleophilic base, such as lithium diisopropylamide, GBL undergoes
deprotonation alpha to the carbonyl.
The related compound caprolactone can be used to make a polyester in this manner.
Pharmacology
GBL is not active in its own right; its mechanism of action stems from its identity as a prodrug
of GHB.
The hypnotic effect of GHB is enhanced by combination with alcohol.
A 2003 rat study showed that GBL in combination with ethanol showed a potentiated hypnotic
effect, as the sleep-timing measure was longer than both of the individual components combined.
Pharmacokinetics GBL is rapidly converted into GHB by paraoxonase
enzymes, found in the blood.
Animals which lack these enzymes exhibit no effect from GBL.
GBL is more lipophilic than GHB, and so is absorbed faster and has higher bioavailability.
Because of these pharmacokinetic differences, GBL tends to be more potent and faster-acting
than GHB, but has a shorter duration; whereas the related compound 1,4-butanediol tends
to be slightly less potent, slower to take effect but longer-acting than GHB.
The levels of lactonase enzyme can vary between individuals, meaning that first-time users
can show unpredictable results, even from small doses.
In many this manifests as slow onset of effects, followed by headaches, semi-consciousness
which is distinct from GBL sleep in normal users.
If the user decides to try again at a later date, they appear to be able to enjoy the
effects normally.
Use as a nutritional supplement
Due to its property of being a prodrug of GHB which increases sleep related growth hormone
secretion, GBL was sold as a nutritional supplement after the scheduling of GHB, under the names
Revivarant and Renewtrient in the U.S. at least until the end of 1999.
Recreational use GBL is a prodrug of GHB and its recreational
use comes entirely as a result of this.
To bypass GHB restriction laws, home synthesis kits were introduced to transform GBL and/or
1,4-B into GHB.
GBL overdose can cause irrational behaviour, severe sickness, coma and death.
GBL has a distinctive taste and odour, described as being comparable to stale water, synthetic
melon aroma or burnt plastic.
This differs significantly from GHB, which is described as having a decidedly "salty"
taste.
Dangers If taken undiluted by mouth, GBL can cause
esophageal and gastro-intestinal irritation.
It is possible for oral ingestion of GBL to cause nausea and other similar problems, possibly
more so than with GHB.
GHB has biphasic effects, a euphoric effect at low doses, and a sedative effect at higher
doses.
As a result of this sedation it can cause unconsciousness.
When combined with alcohol the increased sedation and risk of vomiting results in a high risk
of fatality.
Many harm reduction organisations suggest never mixing the two drugs as a result.
There have been news reports of several deaths associated with GBL, usually in combination
with alcohol or other depressants.
Addictiveness Frequent use of GHB/GBL, even when taken long-term
and in moderate doses, does not appear to cause significant physical dependency in the
greater majority of its users.
In many people, quitting or temporarily abstaining from use of the drugs is achieved with minimal
or no difficulty.
However, when consumed in excessive amounts with a high frequency of dosing, physical
and psychological dependence can develop.
There are some reports of GHB/GBL users adopting a '24/7' dosing regime.
This is where the user has become tolerant to the effects of the drug, increasing the
dosage and frequency of dosage simply to avoid withdrawal symptoms.
For those users who do report withdrawal symptoms upon quitting the use of GHB/GBL, symptoms
seem to depend on the dosage and the length of time the drug was used for.
Light to moderate users often experience insomnia and sleep-related problems, whereas heavy,
prolonged use can cause severe withdrawal symptoms similar to Benzodiazepine withdrawal
syndrome.
Dose A milliliter of pure GBL metabolizes to the
equivalent 1.65g of NaGHB, the common form, so doses are measured in the single milliliter
range, either taken all at once or sipped over the course of a night.
Legal status of GBL Australia: GBL is a border controlled substance
and is illegal to import into Australia without a permit.
The importation of a commercial quantity of a border controlled drug is punishable by
up to life imprisonment and/or an $825,000 fine.
Canada: GBL is a Controlled Substance under Schedule VI of the "Controlled Drugs and Substances
Act" in Canada.
Schedule VI of the "Controlled Drugs and Substances Act" requires vendors to collect information
regarding purchases of GBL.
The Act also prohibits the import and export of GBL into or out of Canada classifying it
as either an indictable offense punishable with up to 10 years in prison or an offense
punishable on summary conviction liable to imprisonment for up to eighteen months.
It is not illegal for an individual to possess GBL in Canada.
Germany: GBL is not listed in the narcotics law, but its distribution is controlled.
Possession is not illegal, but may be punished according to the Medicines Act, when intended
to be sold for human consumption or synthesis of GHB.
In recent years, an increase of GBL consumption has been observed due to the prohibition of
GHB.
Hong Kong SAR: GBL is a dangerous drug controlled under Schedule 1 of the Dangerous Drugs Ordinance,
Cap.134.
Any person who is found to have in his possession of it not in accordance with this Ordinance
can be liable, on conviction upon indictment, a fine of HK$1,000,000 and to imprisonment
for 7 years.
Israel: GBL was classified as a proscribed substance from 2007.
The Netherlands: GBL can be freely bought as a cleaning agent.
Retailers do not need a licence to sell the substance.
Poland: GBL is not classified as a drug and can be purchased in chemistry shops as a solvent.
Russia: GBL is classified as psychotropic substance since 22 February 2012, its traficking
is limited, and non-licensed selling, buying or any other using is imprisoned up to 20
years.
Sweden: GBL is not classified as a drug but as a health-endangering substance.
Although recently passed legislation to enter into force on 1 April 2011 will make it possible
to handle narcotics for industrial purposes will enable GBL and 1,4-Butanediol to be classified
as controlled substances.
United Kingdom: Because of their legitimate uses, regulation 4B of the 2001 regulations
makes it lawful to import, export, produce, supply, offer to supply or possess GBL and
1,4-BD.
Except where a person does so knowing or believing that they will be used for the purpose of
human ingestion.
United States: GBL is regulated as a List 1 controlled chemical.
As a GHB analog, it is treated as a controlled substance under Schedule I of the "Controlled
Substances Act" if intended for human consumption.
See also 1,4-Butanediol
Succinic anhydride References
External links Erowid on GBL
"The paint stripper drug that kills".
BBC News.
October 7, 2005.
"All About GHB," a NIDA Neuroscience Consortium and OSPC "Cutting Edge" colloquium