Clinical data | |
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Trade names | Frisium, Urbanol, Onfi, others |
AHFS/Drugs.com | Monograph |
MedlinePlus | a612008 |
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Routes of administration | By mouth |
Drug class | Benzodiazepine |
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Pharmacokinetic data | |
Bioavailability | 87% (oral) |
Protein binding | 80–90% |
Metabolism | Liver |
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Onset of action | 0.5–4 hours |
Elimination half-life |
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CompTox Dashboard (EPA) | |
ECHA InfoCard | 100.040.810 |
Chemical and physical data | |
Formula | C16H13ClN2O2 |
Molar mass | 300.74 g·mol−1 |
3D model (JSmol) | |
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Clobazam, sold under the brand names Frisium, Onfi and others, is a benzodiazepine class medication that was patented in 1968. [3] Clobazam was first synthesized in 1966 and first published in 1969. Clobazam was originally marketed as an anxioselective anxiolytic since 1970, [4] [5] and an anticonvulsant since 1984. [6] The primary drug-development goal was to provide greater anxiolytic, anti-obsessive efficacy with fewer benzodiazepine-related side effects. [4]
Clobazam is used for its anxiolytic effect, and as an adjunctive therapy in epilepsy.
As an adjunctive therapy in epilepsy, it is used in patients who have not responded to first-line drugs and in children who are refractory to first-line drugs. It is unclear if there are any benefits to clobazam over other seizure medications for children with Rolandic epilepsy or other epileptic syndromes. [7] It is not recommended for use in children between the ages of six months and three years, unless there is a compelling need. [8] In addition to epilepsy and severe anxiety, clobazam is approved in the United Kingdom as a short-term (2–4 weeks) adjunctive agent in schizophrenia and other psychotic disorders to manage anxiety or agitation. [8] [9]
Clobazam is sometimes used for refractory epilepsies. However, long-term prophylactic treatment of epilepsy may have considerable drawbacks, most importantly decreased antiepileptic effects due to drug tolerance which may render long-term therapy less effective. [10] Other antiepileptic drugs may therefore be preferred for the long-term management of epilepsy. Furthermore, benzodiazepines may have the drawback, particularly after long-term use, of causing rebound seizures upon abrupt or over-rapid discontinuation of therapy forming part of the benzodiazepine withdrawal syndrome.
Clobazam is approved in Canada for add-on use in tonic-clonic, complex partial, and myoclonic seizures. [11] Clobazam is approved for adjunctive therapy in complex partial seizures, [12] certain types of status epilepticus, specifically the myoclonic, myoclonic-absent, simple partial, complex partial, and tonic varieties, [13] and non-status absence seizures. It is also approved for the treatment of anxiety.
In India, clobazam is approved for use as an adjunctive therapy in epilepsy, and in acute and chronic anxiety. [14] In Japan, clobazam is approved for adjunctive therapy in treatment-resistant epilepsy featuring complex partial seizures. [15] In New Zealand, clobazam is marketed as Frisium [16] In the United Kingdom clobazam (Frisium) is approved for short-term (2–4 weeks) relief of acute anxiety in patients who have not responded to other drugs, with or without insomnia and without uncontrolled clinical depression. [8] It was not approved in the United States until 25 October 2011, when it was approved for the adjunctive treatment of seizures associated with Lennox-Gastaut syndrome in patients 2 years of age or older. [17]
The current FDA indicated for use in combination with other medicines is to control seizures in adults and children 2 years and older who have a specific severe form of epilepsy called Lennox-Gastaut syndrome. Clobazam has been FDA-approved for 12 years as of 2023 [18] and it is available in multiple formulations under the brand names Onfi and Sympazan as well as generic formulations.
Clobazam should be used with great care in patients with the following disorders:
Benzodiazepines require special precaution if used in the elderly, during pregnancy, in children, alcohol or drug-dependent individuals, and individuals with comorbid psychiatric disorders. [20]
In September 2020, the U.S. Food and Drug Administration (FDA) required the boxed warning be updated for all benzodiazepine medicines to describe the risks of abuse, misuse, addiction, physical dependence, and withdrawal reactions consistently across all the medicines in the class. [21]
Common side effects include fever, drooling, and constipation. [22]
In December 2013, the FDA added warnings to the label for clobazam, that it can cause serious skin reactions, Stevens–Johnson syndrome, and toxic epidermal necrolysis, especially in the first eight weeks of treatment. [23]
Overdose and intoxication with benzodiazepines, including clobazam, may lead to CNS depression, associated with drowsiness, confusion, and lethargy, possibly progressing to ataxia, respiratory depression, hypotension, and coma or death. The risk of a fatal outcome is increased in cases of combined poisoning with other CNS depressants, including alcohol. [24]
Classic (non-anxioselective) benzodiazepines in animal studies have been shown to increase reward-seeking behaviours which may suggest an increased risk of addictive behavioural patterns. [25] Clobazam abuse has been reported in some countries, according to a 1983 World Health Organization report. [26]
In humans, tolerance to the anticonvulsant effects of clobazam may occur [27] and withdrawal seizures may occur during abrupt or over-rapid withdrawal. [28]
Clobazam as with other benzodiazepine drugs can lead to physical dependence, addiction, and what is known as the benzodiazepine withdrawal syndrome. Withdrawal from clobazam or other benzodiazepines after regular use often leads to withdrawal symptoms which are similar to those seen during alcohol and barbiturate withdrawal. The higher the dosage and the longer the drug is taken, the greater the risk of experiencing unpleasant withdrawal symptoms. Benzodiazepine treatment should only be discontinued via a slow and gradual dose reduction regimen. [29]
Clobazam is predominantly a positive allosteric modulator at the GABAA receptor with some speculated additional activity at sodium channels and voltage-sensitive calcium channels. [30]
Like other 1,5-benzodiazepines (for example, arfendazam, lofendazam, or CP-1414S), the active metabolite N-desmethylclobazam has less affinity for the α1 subunit of the GABAA receptor compared to the 1,4-benzodiazepines. It has higher affinity for α2 containing receptors, where it has positive modulatory activity. [31] [32]
In a double-blind placebo-controlled trial published in 1990 comparing it to clonazepam, 10 mg of clobazam was shown to be less sedative than either 0.5 mg or 1 mg of clonazepam. [33]
The α1 subtype of the GABAA receptor, was shown to be responsible for the sedative effects of diazepam by McKernan et al. in 2000, who also showed that its anxiolytic and anticonvulsant properties could still be seen in mice whose α1 receptors were insensitive to diazepam. [34]
In 1996, Nakamura et al. reported that clobazam and its active metabolite, N-desmethylclobazam (norclobazam), work by enhancing GABA-activated chloride influx at GABAA receptors, [35] creating a hyperpolarizing, inhibitory postsynaptic potential. [36] It was also reported that these effects were inhibited by the GABA antagonist flumazenil, and that clobazam acts more efficiently in GABA-deficient brain tissue. [35]
Clobazam has two major metabolites: N-desmethylclobazam and 4′-hydroxyclobazam, the former of which is active. [37] The demethylation is facilitated by CYP2C19, CYP3A4, and CYP2B6 and the 4-hydroxyclobazam by CYP2C18 and CYP2C19. [38]
In children, clobazam half-life values is average 16 hours, while in the elderly, clobazam half-life values are 30 to 48 hours. [39] [40]
Clobazam is a 1,5-benzodiazepine, meaning that its diazepine ring has nitrogen atoms at the 1 and 5 positions (instead of the usual 1 and 4). [41]
It is not soluble in water and is available in oral form only. [30] [24]
Clobazam was discovered at the Maestretti Research Laboratories in Milan and was first published in 1969; [42] Maestretti was acquired by Roussel Uclaf [43] which became part of Sanofi.
Benzodiazepines, colloquially known as "benzos", are a class of depressant drugs whose core chemical structure is the fusion of a benzene ring and a diazepine ring. They are prescribed to treat conditions such as anxiety disorders, insomnia, and seizures. The first benzodiazepine, chlordiazepoxide (Librium), was discovered accidentally by Leo Sternbach in 1955, and was made available in 1960 by Hoffmann–La Roche, which followed with the development of diazepam (Valium) three years later, in 1963. By 1977, benzodiazepines were the most prescribed medications globally; the introduction of selective serotonin reuptake inhibitors (SSRIs), among other factors, decreased rates of prescription, but they remain frequently used worldwide.
Anticonvulsants are a diverse group of pharmacological agents used in the treatment of epileptic seizures. Anticonvulsants are also increasingly being used in the treatment of bipolar disorder and borderline personality disorder, since many seem to act as mood stabilizers, and for the treatment of neuropathic pain. Anticonvulsants suppress the excessive rapid firing of neurons during seizures. Anticonvulsants also prevent the spread of the seizure within the brain.
Diazepam, sold under the brand name Valium among others, is a medicine of the benzodiazepine family that acts as an anxiolytic. It is used to treat a range of conditions, including anxiety, seizures, alcohol withdrawal syndrome, muscle spasms, insomnia, and restless legs syndrome. It may also be used to cause memory loss during certain medical procedures. It can be taken orally, as a suppository inserted into the rectum, intramuscularly, intravenously or used as a nasal spray. When injected intravenously, effects begin in one to five minutes and last up to an hour. When taken by mouth, effects begin after 15 to 60 minutes.
Lorazepam, sold under the brand name Ativan among others, is a benzodiazepine medication. It is used to treat anxiety, trouble sleeping, severe agitation, active seizures including status epilepticus, alcohol withdrawal, and chemotherapy-induced nausea and vomiting. It is also used during surgery to interfere with memory formation, to sedate those who are being mechanically ventilated, and, along with other treatments, for acute coronary syndrome due to cocaine use. It can be given orally, transdermally, intravenously (IV), or intramuscularly When given by injection, onset of effects is between one and thirty minutes and effects last for up to a day.
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.
Clonazepam, sold under the brand name Klonopin among others, is a benzodiazepine medication used to prevent and treat anxiety disorders, seizures, bipolar mania, agitation associated with psychosis, obsessive–compulsive disorder (OCD), and akathisia. It is a long-acting tranquilizer of the benzodiazepine class. It possesses anxiolytic, anticonvulsant, sedative, hypnotic, and skeletal muscle relaxant properties. It is typically taken orally but is also used intravenously. Effects begin within one hour and last between eight and twelve hours in adults.
The GABAA receptor (GABAAR) is an ionotropic receptor and ligand-gated ion channel. Its endogenous ligand is γ-aminobutyric acid (GABA), the major inhibitory neurotransmitter in the central nervous system. Accurate regulation of GABAergic transmission through appropriate developmental processes, specificity to neural cell types, and responsiveness to activity is crucial for the proper functioning of nearly all aspects of the central nervous system (CNS). Upon opening, the GABAA receptor on the postsynaptic cell is selectively permeable to chloride ions and, to a lesser extent, bicarbonate ions.
Tiagabine is an anticonvulsant medication produced by Cephalon that is used in the treatment of epilepsy. The drug is also used off-label in the treatment of anxiety disorders and panic disorder.
Stiripentol, sold under the brand name Diacomit, is an anticonvulsant medication used for the treatment of Dravet syndrome - a serious genetic brain disorder.
Progabide is an analogue and prodrug of γ-aminobutyric acid (GABA) used in the treatment of epilepsy. Via conversion into GABA, progabide behaves as an agonist of the GABAA, GABAB, and GABAA-ρ receptors.
Clorazepate, sold under the brand name Tranxene among others, is a benzodiazepine medication. It possesses anxiolytic, anticonvulsant, sedative, hypnotic, and skeletal muscle relaxant properties. Clorazepate is an unusually long-lasting benzodiazepine and serves as a prodrug for the equally long-lasting desmethyldiazepam, which is rapidly produced as an active metabolite. Desmethyldiazepam is responsible for most of the therapeutic effects of clorazepate.
Felbamate is an anticonvulsant used in the treatment of epilepsy. It is used to treat partial seizures in adults and partial and generalized seizures associated with Lennox–Gastaut syndrome in children. However, an increased risk of potentially fatal aplastic anemia and/or liver failure limit the drug's usage to severe refractory epilepsy.
Rufinamide is an anticonvulsant medication. It is used in combination with other medication and therapy to treat Lennox–Gastaut syndrome and various other seizure disorders. Rufinamide, a triazole derivative, was developed in 2004 by Novartis Pharma, AG, and is manufactured by Eisai.
Dravet syndrome (DS), previously known as severe myoclonic epilepsy of infancy (SMEI), is an autosomal dominant genetic disorder which causes a catastrophic form of epilepsy, with prolonged seizures that are often triggered by hot temperatures or fever. It is very difficult to treat with anticonvulsant medications. It often begins before one year of age, with six months being the age that seizures, characterized by prolonged convulsions and triggered by fever, usually begin.
Imidazenil is an experimental anxiolytic drug which is derived from the benzodiazepine family, and is most closely related to other imidazobenzodiazepines such as midazolam, flumazenil, and bretazenil.
Lacosamide, sold under the brand name Vimpat among others, is a medication used for the treatment of partial-onset seizures and primary generalized tonic-clonic seizures. It is used by mouth or intravenously.
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Barbiturates are a class of depressant drugs that are chemically derived from barbituric acid. They are effective when used medically as anxiolytics, hypnotics, and anticonvulsants, but have physical and psychological addiction potential as well as overdose potential among other possible adverse effects. They have been used recreationally for their anti-anxiety and sedative effects, and are thus controlled in most countries due to the risks associated with such use.
Perampanel, sold under the brand name Fycompa, is an anti-epileptic medication developed by Eisai Co. that is used in addition to other drugs to treat partial seizures and generalized tonic-clonic seizures for people older than twelve years. It was first approved in 2012, and as of 2016, its optimal role in the treatment of epilepsy relative to other drugs was not clear. It was the first antiepileptic drug in the class of selective non-competitive antagonist of AMPA receptors.