Clinical data | |
---|---|
Trade names | Lioresal, Liofen, Gablofen, others |
Other names | β-(4-chlorophenyl)-γ-aminobutyric acid (β-(4-chlorophenyl)-GABA) |
AHFS/Drugs.com | Monograph |
MedlinePlus | a682530 |
License data | |
Pregnancy category |
|
Routes of administration | oral, intrathecal, transdermal |
ATC code | |
Legal status | |
Legal status | |
Pharmacokinetic data | |
Bioavailability | Well-absorbed |
Protein binding | 30% |
Metabolism | 85% excreted in urine/faeces unchanged. 15% metabolised by deamination |
Elimination half-life | 1.5 to 4 hours |
Excretion | Kidney (70–80%) |
Identifiers | |
| |
CAS Number | |
PubChem CID | |
IUPHAR/BPS | |
DrugBank | |
ChemSpider | |
UNII | |
KEGG | |
ChEBI | |
ChEMBL | |
CompTox Dashboard (EPA) | |
ECHA InfoCard | 100.013.170 |
Chemical and physical data | |
Formula | C10H12ClNO2 |
Molar mass | 213.66 g·mol−1 |
3D model (JSmol) | |
Chirality | Racemic mixture |
| |
| |
(verify) |
Baclofen, sold under the brand name Lioresal among others, is a medication used to treat muscle spasticity such as from a spinal cord injury or multiple sclerosis. [8] [9] It may also be used for hiccups and muscle spasms near the end of life, [9] and off-label to treat alcohol use disorder [10] [11] or opioid withdrawal symptoms. [12] It is taken orally (swallowed by mouth) or by intrathecal pump (delivered into the spinal canal via an implantable pump device). [8] It is also sometimes used transdermally (applied topically to the skin) in combination with gabapentin and clonidine prepared at a compounding pharmacy. [13]
Common side effects include sleepiness, weakness, and dizziness. [8] Serious side effects may occur if baclofen is rapidly stopped including seizures and rhabdomyolysis. [8] Use in pregnancy is of unclear safety while use during breastfeeding is probably safe. [14] It is believed to work by decreasing levels of certain neurotransmitters. [8]
The adverse effects and safety profile associated with baclofen when it is combined with sedative drugs (for example alcohol or benzodiazepines) range depending on the dose and the individual. The interaction may increase the sedative effects of all ingested sedatives and as such is not generally recommended. [15] In high doses the interaction can cause de novo seizures. [16]
Baclofen was approved for medical use in the United States in 1977. [8] It is available as a generic medication. [9] [17] In 2022, it was the 104th most commonly prescribed medication in the United States, with more than 6 million prescriptions. [18] [19]
Baclofen is primarily used for the treatment of spastic movement disorders, especially in instances of spinal cord injury, cerebral palsy, and multiple sclerosis. [20] Use in people with stroke or Parkinson's disease is not recommended. [20] Intrathecal baclofen is used for severe spasticity of spinal cord origin that is refractive to maximum doses of oral antispasmodic agents or who experience intolerable side effects. [21] [22] Baclofen is also used in the treatment of sleep-related painful erections. [23]
Baclofen is sometimes used off-label as a treatment for alcohol use disorder to reduce the risk of relapse and to increase the number of days that a person can go without drinking alcohol (abstinence days). [10] It is also sometimes used for the treatment of opioid withdrawal symptoms, and may be superior for this purpose to the more-commonly used clonidine. [11] [12]
Adverse effects include drowsiness, dizziness, weakness, fatigue, headache, trouble sleeping, nausea and vomiting, poor concentration and recall (resembling dementia), urinary retention, or constipation. [3]
Discontinuation of baclofen can be associated with a withdrawal syndrome which resembles benzodiazepine withdrawal and alcohol withdrawal. Withdrawal symptoms are more likely if baclofen is administered intrathecally or for long periods of time (more than a couple of months) and can occur from low or high doses. [24] The severity of baclofen withdrawal depends on the rate at which it is discontinued. Thus to minimise withdrawal symptoms, the dose should be tapered down slowly when discontinuing baclofen therapy. Abrupt withdrawal is more likely to result in severe withdrawal symptoms. Acute withdrawal symptoms can be eased or completely reversed by re-initiating therapy with baclofen. [25]
Withdrawal symptoms may include auditory hallucinations, visual hallucinations, tactile hallucinations, delusions, confusion, agitation, delirium, disorientation, fluctuation of consciousness, insomnia, dizziness, nausea, inattention, memory impairments, perceptual disturbances, itching, anxiety, depersonalization, hypertonia, hyperthermia (higher than normal temperature without infection), formal thought disorder, psychosis, mania, mood disturbances, restlessness, and behavioral disturbances, tachycardia, seizures, tremors, autonomic dysfunction, hyperpyrexia (fever), extreme muscle rigidity resembling neuroleptic malignant syndrome and rebound spasticity. [25] [24]
Baclofen, at standard dosing, does not appear to possess addictive properties, and has not been associated with any degree of drug craving. [26] [27] Euphoria is however listed as a common to very common side-effect of baclofen in the BNF 75. [28] There are very few cases of abuse of baclofen for reasons other than attempted suicide. [26] In contrast to baclofen, another GABAB receptor agonist, γ-hydroxybutyric acid (GHB), has been associated with euphoria, abuse, and addiction. [29] These effects are likely mediated not by activation of the GABAB receptor, but rather by activation of the GHB receptor. [29] Baclofen possesses both sedative and anxiolytic properties. [27]
Reports of overdose indicate that baclofen may cause symptoms including vomiting, general weakness, sedation, respiratory insufficiency, seizures, unusual pupil size[ clarification needed ], dizziness, [3] headaches, [3] itching, hypothermia, bradycardia, cardiac conduction abnormalities, hypertension, hyporeflexia and coma sometimes mimicking brain death. [30] Overdose may require intubation and length of mechanical ventilation required may correlate with serum baclofen levels shortly after ingestion. Symptoms may persist even after the point at which serum baclofen levels are undetectable. [31]
Chemically, baclofen is a derivative of the neurotransmitter γ-aminobutyric acid (GABA). It is believed to work by activating (or agonizing) GABA receptors, specifically the GABAB receptors. [32]
Baclofen produces its effects by selectively activating the GABAB receptor. Baclofen is postulated to block mono-and-polysynaptic reflexes by acting as an inhibitory ligand, inhibiting the release of excitatory neurotransmitters. Baclofen does not have significant affinity for the GHB receptor, and has no known abuse potential. [33] Agonism of GABAB receptors is thought to be responsible for baclofen's range of therapeutic properties, as GABAB knockout mice are unresponsive to the neurobiological effects of baclofen. [34]
Similarly to phenibut (β-phenyl-GABA), as well as pregabalin (β-isobutyl-GABA), which are close analogues of baclofen, baclofen (β-(4-chlorophenyl)-GABA) has been found to block α2δ subunit-containing voltage-gated calcium channels (VGCCs). [35] However, it is weaker relative to phenibut in this action (Ki = 23 and 39 μM for R- and S-phenibut and 156 μM for baclofen). [35] Moreover, baclofen is in the range of 100-fold more potent by weight as an agonist of the GABAB receptor in comparison to phenibut, and in accordance, is used at far lower relative dosages. As such, the actions of baclofen on α2δ subunit-containing VGCCs are likely not clinically relevant. [35]
For drug-reward and addiction, baclofen's mechanism of action is thought to be through its effect on the mesolimbic dopamine pathway, specifically leading to a decrease in dopamine release associated with alcohol. [10] GABAB receptor activation (GABAB receptor agonist activity) may decrease or inhibit alcohol's ability to activate or fire dopaminergic neurons following exposure to alcohol. Baclofen's mechanism of action when used to treat alcohol use disorder is not thought to be mediated through its muscle-relaxing or sedative properties, however there is evidence to suggest that the GABAB receptor-activation in the limbus may also reduce feelings of anxiety in people with alcohol use disorder. [10]
The drug is rapidly absorbed after oral administration and is widely distributed throughout the body. Biotransformation is low: the drug is predominantly excreted unchanged by the kidneys. [36] The half-life of baclofen is roughly 2–4 hours; it therefore needs to be administered frequently throughout the day to control spasticity appropriately.
Baclofen is a white (or off-white) mostly odorless crystalline powder, with a molecular weight of 213.66 g/mol. It is slightly soluble in water, very slightly soluble in methanol, and insoluble in chloroform.
Historically, baclofen was designed as a drug for treating epilepsy. It was first synthesized at Ciba-Geigy, by the Swiss chemist Heinrich Keberle, in 1962. [37] [38] Its effect on epilepsy was disappointing, but it was found that in certain people, spasticity decreased. In 1971, it was introduced as a treatment for certain form of spasticity. It was approved by the US Food and Drug Administration (FDA) in 1977. [39]
Intrathecal baclofen was first introduced in 1984 to treat severe spinal spasticity. This administration route aimed to avoid supraspinal side effects. [40] [41]
In his 2008 book, Le Dernier Verre (translated literally as The Last Glass or The End of my Addiction), French-American cardiologist Olivier Ameisen described how he treated his alcoholism with baclofen. Inspired by this book, an anonymous donor gave $750,000 to the University of Amsterdam in the Netherlands to initiate a clinical trial of high-dose baclofen, which Ameisen had called for since 2004. [42] The trial concluded, "In summary, the current study did not find evidence of a positive effect of either low or high doses of baclofen in AD patients. However, we cannot exclude the possibility that baclofen is an effective medication for the treatment of severe, heavy drinking AD patients not responding to or not accepting routine psychosocial interventions." [43]
Baclofen can be administered, orally, intrathecally (directly into the cerebral spinal fluid) using a pump implanted under the skin, or transdermally as part of a pain-relieving and muscle-relaxing topical cream mix (also containing gabapentin and clonidine) prepared at a compounding pharmacy. [13] [44]
Intrathecal pumps offer much lower doses of baclofen because they are designed to deliver the medication directly to the spinal fluid rather than going through the digestive and blood system first. A drug concentration in the cerebrospinal fluid more than 10 times greater than when given orally is achieved with this route. At the same time the blood concentration levels are almost undetectable, thus minimizing side effects. [44]
Besides those with spasticity, intrathecal administration is also used in patients with cerebral palsy [44] or multiple sclerosis who have severe painful spasms which are not controllable by oral baclofen.[ citation needed ] With pump administration, a test dose is first injected into the spinal fluid to assess the effect, and if successful in relieving spasticity, a chronic intrathecal catheter is inserted from the spine through the abdomen and attached to the pump which is implanted under the abdomen's skin, usually by the ribcage.[ citation needed ] The pump is computer-controlled for automatic dosage and its reservoir can be replenished by percutaneous injection.[ citation needed ] The pump also has to be replaced every five to seven years or so. [45]
Synonyms include chlorophenibut. Brand names include Beklo, Baclodol, Flexibac, Gablofen, Kemstro, Liofen, Lioresal, Lyflex, Clofen, Muslofen, Bacloren, Baklofen, Sclerofen, Pacifen and others.
Baclofen is being studied for the treatment of alcoholism. [26] Evidence as of 2019 is not conclusive enough to recommend its use for this purpose. [26] [46] In 2014, the French drug agency ANSM issued a three-year temporary recommendation allowing the use of baclofen in alcoholism. [47] In 2018, baclofen received a Marketing Authorization for use in alcoholism treatment from the agency if all other treatments are not effective. [48]
It is being studied along with naltrexone and sorbitol for Charcot–Marie–Tooth disease (CMT), a hereditary disease that causes peripheral neuropathy. [49] It is also being studied for cocaine addiction. [50] Baclofen and other muscle relaxants are being studied for potential use for persistent hiccups. [51] [52]
From 2014 to 2017 baclofen misuse, toxicity and use in suicide attempts among adults in the US increased. [53]
An anxiolytic is a medication or other intervention that reduces anxiety. This effect is in contrast to anxiogenic agents which increase anxiety. Anxiolytic medications are used for the treatment of anxiety disorders and their related psychological and physical symptoms.
A muscle relaxant is a drug that affects skeletal muscle function and decreases the muscle tone. It may be used to alleviate symptoms such as muscle spasms, pain, and hyperreflexia. The term "muscle relaxant" is used to refer to two major therapeutic groups: neuromuscular blockers and spasmolytics. Neuromuscular blockers act by interfering with transmission at the neuromuscular end plate and have no central nervous system (CNS) activity. They are often used during surgical procedures and in intensive care and emergency medicine to cause temporary paralysis. Spasmolytics, also known as "centrally acting" muscle relaxant, are used to alleviate musculoskeletal pain and spasms and to reduce spasticity in a variety of neurological conditions. While both neuromuscular blockers and spasmolytics are often grouped together as muscle relaxant, the term is commonly used to refer to spasmolytics only.
A sedative or tranquilliser is a substance that induces sedation by reducing irritability or excitement. They are CNS depressants and interact with brain activity causing its deceleration. Various kinds of sedatives can be distinguished, but the majority of them affect the neurotransmitter gamma-aminobutyric acid (GABA). In spite of the fact that each sedative acts in its own way, most produce relaxing effects by increasing GABA activity.
Depressants, colloquially known as "downers" or central nervous system (CNS) depressants, are drugs that lower neurotransmission levels, decrease the electrical activity of brain cells, or reduce arousal or stimulation in various areas of the brain. Some specific depressants do influence mood, either positively or negatively, but depressants often have no clear impact on mood. In contrast, stimulants, or "uppers", increase mental alertness, making stimulants the opposite drug class from depressants. Antidepressants are defined by their effect on mood, not on general brain activity, so they form an orthogonal category of drugs.
Gabapentin, sold under the brand name Neurontin among others, is an anticonvulsant medication primarily used to treat partial seizures and neuropathic pain. It is a commonly used medication for the treatment of neuropathic pain caused by diabetic neuropathy, postherpetic neuralgia, and central pain. It is moderately effective: about 30–40% of those given gabapentin for diabetic neuropathy or postherpetic neuralgia have a meaningful benefit.
Clonidine, sold under the brand name Catapres among others, is an α2A-adrenergic receptor agonist medication used to treat high blood pressure, ADHD, drug withdrawal, menopausal flushing, diarrhea, spasticity, and certain pain conditions. The drug is often prescribed off-label for tics. It is used orally, by injection, or as a transdermal skin patch. Onset of action is typically within an hour with the effects on blood pressure lasting for up to eight hours.
Physical dependence is a physical condition caused by chronic use of a tolerance-forming drug, in which abrupt or gradual drug withdrawal causes unpleasant physical symptoms. Physical dependence can develop from low-dose therapeutic use of certain medications such as benzodiazepines, opioids, stimulants, antiepileptics and antidepressants, as well as the recreational misuse of drugs such as alcohol, opioids and benzodiazepines. The higher the dose used, the greater the duration of use, and the earlier age use began are predictive of worsened physical dependence and thus more severe withdrawal syndromes. Acute withdrawal syndromes can last days, weeks or months. Protracted withdrawal syndrome, also known as post-acute-withdrawal syndrome or "PAWS", is a low-grade continuation of some of the symptoms of acute withdrawal, typically in a remitting-relapsing pattern, often resulting in relapse and prolonged disability of a degree to preclude the possibility of lawful employment. Protracted withdrawal syndrome can last for months, years, or depending on individual factors, indefinitely. Protracted withdrawal syndrome is noted to be most often caused by benzodiazepines. To dispel the popular misassociation with addiction, physical dependence to medications is sometimes compared to dependence on insulin by persons with diabetes.
An intrathecal pump is a medical device used to deliver medications directly into the space between the spinal cord and the protective sheath surrounding the spinal cord. Medications such as baclofen, bupivacaine, clonidine, morphine, hydromorphone, fentanyl or ziconotide may be delivered in this manner to minimize the side effects often associated with the higher doses used in oral or intravenous delivery of these drugs.
Succinic semialdehyde dehydrogenase deficiency (SSADHD) is a rare autosomal recessive disorder of the degradation pathway of the inhibitory neurotransmitter γ-aminobutyric acid, or GABA. The disorder has been identified in approximately 350 families, with a significant proportion being consanguineous families. The first case was identified in 1981 and published in a Dutch clinical chemistry journal that highlighted a number of neurological conditions such as delayed intellectual, motor, speech, and language as the most common manifestations. Later cases reported in the early 1990s began to show that hypotonia, hyporeflexia, seizures, and a nonprogressive ataxia were frequent clinical features as well.
Phenibut, sold under the brand name Anvifen among others, is a central nervous system (CNS) depressant with anxiolytic effects, and is used to treat anxiety, insomnia, and for a variety of other indications. It is usually taken orally, but may be given intravenously.
Alcohol detoxification is the abrupt cessation of alcohol intake in individuals that have alcohol use disorder. This process is often coupled with substitution of drugs that have effects similar to the effects of alcohol in order to lessen the symptoms of alcohol withdrawal. When withdrawal does occur, it results in symptoms of varying severity.
A GABA receptor agonist is a drug that is an agonist for one or more of the GABA receptors, producing typically sedative effects, and may also cause other effects such as anxiolytic, anticonvulsant, and muscle relaxant effects. There are three receptors of the gamma-aminobutyric acid. The two receptors GABA-α and GABA-ρ are ion channels that are permeable to chloride ions which reduces neuronal excitability. The GABA-β receptor belongs to the class of G-Protein coupled receptors that inhibit adenylyl cyclase, therefore leading to decreased cyclic adenosine monophosphate (cAMP). GABA-α and GABA-ρ receptors produce sedative and hypnotic effects and have anti-convulsion properties. GABA-β receptors also produce similar effects. Furthermore, they lead to changes in gene transcription, and are mainly found in autonomic nervous system centers.
γ-Amino-β-hydroxybutyric acid (GABOB), also known as β-hydroxy-γ-aminobutyric acid (β-hydroxy-GABA), sold under the brand name Gamibetal among others, is an anticonvulsant which is used for the treatment of epilepsy in Europe, Japan, and Mexico. It is a GABA analogue, or an analogue of the neurotransmitter γ-aminobutyric acid (GABA), and has been found to be an endogenous metabolite of GABA.
Alcohol withdrawal syndrome (AWS) is a set of symptoms that can occur following a reduction in alcohol use after a period of excessive use. Symptoms typically include anxiety, shakiness, sweating, vomiting, fast heart rate, and a mild fever. More severe symptoms may include seizures, and delirium tremens (DTs); which can be fatal in untreated patients. Symptoms start at around 6 hours after last drink. Peak incidence of seizures occurs at 24-36 hours and peak incidence of delirium tremens is at 48-72 hours.
Benzodiazepine dependence defines a situation in which one has developed one or more of either tolerance, withdrawal symptoms, drug seeking behaviors, such as continued use despite harmful effects, and maladaptive pattern of substance use, according to the DSM-IV. In the case of benzodiazepine dependence, the continued use seems to be typically associated with the avoidance of unpleasant withdrawal reaction rather than with the pleasurable effects of the drug. Benzodiazepine dependence develops with long-term use, even at low therapeutic doses, often without the described drug seeking behavior and tolerance.
Gabapentinoids, also known as α2δ ligands, are a class of drugs that are derivatives of the inhibitory neurotransmitter gamma-Aminobutyric acid (GABA) which block α2δ subunit-containing voltage-dependent calcium channels (VDCCs). This site has been referred to as the gabapentin receptor, as it is the target of the drugs gabapentin and pregabalin.
A GABA analogue is a compound which is an analogue or derivative of the neurotransmitter gamma-Aminobutyric acid (GABA).
4-Fluorophenibut (developmental code name CGP-11130; also known as β-(4-fluorophenyl)-γ-aminobutyric acid or β-(4-fluorophenyl)-GABA) is a GABAB receptor agonist which was never marketed. It is selective for the GABAB receptor over the GABAA receptor (IC50 = 1.70 μM and > 100 μM, respectively). The drug is a GABA analogue and is closely related to baclofen (β-(4-chlorophenyl)-GABA), tolibut (β-(4-methylphenyl)-GABA), and phenibut (β-phenyl-GABA). It is less potent as a GABAB receptor agonist than baclofen but more potent than phenibut.
Opioid withdrawal is a set of symptoms arising from the sudden cessation or reduction of opioids where previous usage has been heavy and prolonged. Signs and symptoms of withdrawal can include drug craving, anxiety, restless legs syndrome, nausea, vomiting, diarrhea, sweating, and an elevated heart rate. Opioid use triggers a rapid adaptation in cellular signaling pathways that, when reduced or stopped, can cause adverse physiological effects. All opioids, both recreational drugs and medications, when reduced or stopped, can lead to opioid withdrawal symptoms. When withdrawal symptoms are due to recreational opioid use, the term opioid use disorder is used, whereas when due to prescribed medications, the term prescription opioid use disorder is used. Opioid withdrawal can be managed by the use of opioid replacement therapy, while symptoms may be relieved by the use of medications such as lofexidine and clonidine.
ADX-71441 is a GABAB receptor positive allosteric modulator currently being investigated as a potential treatment for anxiety, epilepsy, pain and other conditions.