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]
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.
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.
Contraindications
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 comorbidpsychiatric disorders.[20]
Side effects
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
Common side effects include fever, drooling, and constipation.[22]
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]
Dependence and withdrawal
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]
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 antagonistflumazenil, and that clobazam acts more efficiently in GABA-deficient brain tissue.[35]
Metabolism
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]
Chemistry
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]
History
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.
^ abHumayun MJ, Samanta D, Carson RP (2020). "Clobazam". StatPearls. Treasure Island (FL): StatPearls Publishing. PMID31082087.
^Freche C (April 1975). "[Study of an anxiolytic, clobazam, in otorhinolaryngology in psychosomatic pharyngeal manifestations]". Semaine des Hopitaux. Therapeutique. 51 (4): 261–3. PMID5777.
^Isojärvi JI, Tokola RA (December 1998). "Benzodiazepines in the treatment of epilepsy in people with intellectual disability". Journal of Intellectual Disability Research. 42 (Suppl 1): 80–92. PMID10030438.
^"Clobazam". Epilepsy Ontario. 2020. Retrieved 21 August 2020.
^Larrieu JL, Lagueny A, Ferrer X, Julien J (December 1986). "[Epilepsy with continuous discharges during slow-wave sleep. Treatment with clobazam]". Revue d'Electroencephalographie et de Neurophysiologie Clinique (in French). 16 (4): 383–94. doi:10.1016/S0370-4475(86)80028-4. PMID3103177.
^Gastaut H, Tinuper P, Aguglia U, Lugaresi E (December 1984). "[Treatment of certain forms of status epilepticus by means of a single oral dose of clobazam]". Revue d'Electroencephalographie et de Neurophysiologie Clinique. 14 (3): 203–6. doi:10.1016/S0370-4475(84)80005-2. PMID6528075.
^Monjanel-Mouterde S, Antoni M, Bun H, Botta-Frindlund D, Gauthier A, Durand A, et al. (June 1994). "Pharmacokinetics of a single oral dose of clobazam in patients with liver disease". Pharmacology & Toxicology. 74 (6): 345–50. doi:10.1111/j.1600-0773.1994.tb01371.x. PMID7937568.
^Authier N, Balayssac D, Sautereau M, Zangarelli A, Courty P, Somogyi AA, et al. (November 2009). "Benzodiazepine dependence: focus on withdrawal syndrome". Annales Pharmaceutiques Françaises. 67 (6): 408–13. doi:10.1016/j.pharma.2009.07.001. PMID19900604.
^Thiébot MH, Le Bihan C, Soubrié P, Simon P (1985). "Benzodiazepines reduce the tolerance to reward delay in rats". Psychopharmacology. 86 (1–2): 147–52. doi:10.1007/BF00431700. PMID2862657. S2CID30614502.
^MacKinnon GL, Parker WA (1982). "Benzodiazepine withdrawal syndrome: a literature review and evaluation". The American Journal of Drug and Alcohol Abuse. 9 (1): 19–33. doi:10.3109/00952998209002608. PMID6133446.
^McKernan RM, Rosahl TW, Reynolds DS, Sur C, Wafford KA, Atack JR, et al. (June 2000). "Sedative but not anxiolytic properties of benzodiazepines are mediated by the GABA(A) receptor alpha1 subtype". Nature Neuroscience. 3 (6): 587–92. doi:10.1038/75761. PMID10816315. S2CID10340592.
^ abNakamura F, Suzuki S, Nishimura S, Yagi K, Seino M (August 1996). "Effects of clobazam and its active metabolite on GABA-activated currents in rat cerebral neurons in culture". Epilepsia. 37 (8): 728–35. doi:10.1111/j.1528-1157.1996.tb00643.x. PMID8764810. S2CID12628361.
^Contin M, Sangiorgi S, Riva R, Parmeggiani A, Albani F, Baruzzi A (December 2002). "Evidence of polymorphic CYP2C19 involvement in the human metabolism of N-desmethylclobazam". Therapeutic Drug Monitoring. 24 (6): 737–41. doi:10.1097/00007691-200212000-00009. PMID12451290. S2CID44444755.
^Giraud C, Tran A, Rey E, Vincent J, Tréluyer JM, Pons G (November 2004). "In vitro characterization of clobazam metabolism by recombinant cytochrome P450 enzymes: importance of CYP2C19". Drug Metabolism and Disposition. 32 (11): 1279–86. doi:10.1124/dmd.32.11.1279. PMID15483195. S2CID6490031.
^Patsalos PN (2022). "Clobazam". In Patsalos PN (ed.). Antiseizure Medication Interactions: A Clinical Guide. Cham: Springer International Publishing. pp. 55–59. doi:10.1007/978-3-030-82790-8_7. ISBN978-3-030-82790-8.