Flumazenil

Flumazenil
Clinical data
Trade namesAnexate, Lanexat, Mazicon, others
Other namesethyl 8-fluoro- 5,6-dihydro- 5-methyl- 6-oxo- 4H- imidazo [1,5-a] [1,4] benzodiazepine- 3-carboxylate
AHFS/Drugs.comMonograph
Pregnancy
category
  • AU: B3
Routes of
administration		Intranasal, intravenous
ATC code
Legal status
Legal status
Pharmacokinetic data
MetabolismHepatic
Elimination half-life7–15 min (initial)
20–30 min (brain)
40–80 min (terminal)
ExcretionUrine 90–95%
Feces 5–10%
Identifiers
  • Ethyl 8-fluoro-5-methyl-6-oxo-5,6-dihydro-4H-benzo[f]imidazo[1,5-a][1,4]diazepine-3-carboxylate
CAS Number
PubChem CID
IUPHAR/BPS
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UNII
KEGG
ChEBI
ChEMBL
CompTox Dashboard (EPA)
ECHA InfoCard100.128.069 Edit this at Wikidata
Chemical and physical data
FormulaC15H14FN3O3
Molar mass303.293 g·mol−1
3D model (JSmol)
  • Fc(c1)ccc-2c1C(=O)N(C)Cc3n2cnc3C(=O)OCC
  • InChI=1S/C15H14FN3O3/c1-3-22-15(21)13-12-7-18(2)14(20)10-6-9(16)4-5-11(10)19(12)8-17-13/h4-6,8H,3,7H2,1-2H3 checkY
  • Key:OFBIFZUFASYYRE-UHFFFAOYSA-N checkY
  (verify)
A vial of flumazenil solution for injection

Flumazenil (also known as flumazepil, code name Ro 15-1788[3]) is a selective GABAA receptor antagonist[4] administered via injection, otic insertion, or intranasally. Therapeutically, it acts as both an antagonist and antidote to benzodiazepines (particularly in cases of overdose), through competitive inhibition.

It was first characterized in 1981,[5] and was first marketed in 1987 by Hoffmann-La Roche under the trade name Anexate. However, it did not receive FDA approval until December 20, 1991. The developer lost its exclusive patent rights in 2008; so at present, generic formulations of this drug are available. Intravenous flumazenil is primarily used to treat benzodiazepine overdoses and to help reverse anesthesia. Administration of flumazenil by sublingual lozenge and topical cream has also been tested.[6][7]

Medical uses

[edit]

Flumazenil benefits patients who become excessively drowsy after use of benzodiazepines for either diagnostic or therapeutic procedures.[8]

The drug has been used as an antidote in the treatment of benzodiazepine overdoses.[8] It reverses the effects of benzodiazepines by competitive inhibition at the benzodiazepine (BZ) recognition site on the GABA/benzodiazepine receptor complex. There are many complications that must be taken into consideration when used in the acute care setting.[8] These include lowered seizure threshold, agitation, and anxiousness. Flumazenil's short half-life requires multiple doses. Because of the potential risks of withdrawal symptoms and the drug's short half-life, patients must be carefully monitored to prevent recurrence of overdose symptoms or adverse side effects.

Flumazenil is also sometimes used after surgery to reverse the sedative effects of benzodiazepines. This is similar to naloxone's application to reverse the effect of opiates and opioids following surgery. Administration of the drug requires careful monitoring by an anesthesiologist due to potential side effects and serious risks associated with over-administeration. Likewise, post-surgical monitoring is also necessary because flumazenil can mask the apparent metabolization ("wearing off") of the drug after removal of patient life-support and monitoring equipment.

Flumazenil has been effectively used to treat overdoses of non-benzodiazepine hypnotics, such as zolpidem, zaleplon and zopiclone (also known as "Z-drugs").[9]

It may also be effective in reducing excessive daytime sleepiness while improving vigilance in primary hypersomnias, such as idiopathic hypersomnia.[6]

The drug has also been used in hepatic encephalopathy. It may have beneficial short‐term effects in people with cirrhosis, but there is no evidence for long-term benefits.[10]

The onset of action is rapid, and effects are usually seen within one to two minutes. The peak effect is seen at six to ten minutes. The recommended dose for adults is 200 μg every 1–2 minutes until the effect is seen, up to a maximum of 3 mg per hour. It is available as a clear, colourless solution for intravenous injection, containing 500 μg in 5 mL.[citation needed] Additional doses may be needed within 20 to 30 minutes if evidence of oversedation reappears.[11]

Many benzodiazepines (including midazolam) have longer half-lives than flumazenil. Therefore, in cases of overdose, repeated doses of flumazenil may be required to prevent recurrent symptoms once the initial dose of flumazenil wears off.[citation needed]

It is hepatically metabolised to inactive compounds which are excreted in the urine. Individuals who are physically dependent on benzodiazepines may experience benzodiazepine withdrawal symptoms, including seizures, upon rapid administration of flumazenil.

It is not recommended for routine use in those with a decreased level of consciousness.[12]

In terms of drug enforcement initiatives, diversion control programs and required post-marketing surveillance of adverse events, orders for flumazenil may trigger a prescription audit to the search for benzodiazepine misuse and for clinically significant adverse reactions related to their use.[13]

PET radioligand

[edit]

Radiolabeled with the radioactive isotope carbon-11, flumazenil may be used as a radioligand in neuroimaging with positron emission tomography to visualize the distribution of GABAA receptors in the human brain.[14]

Treatment for benzodiazepine dependence & tolerance

[edit]

Epileptic patients who have become tolerant to the anti-seizure effects of the benzodiazepine clonazepam became seizure-free for several days after treatment with 1.5 mg of flumazenil.[15] Similarly, patients who were dependent on high doses of benzodiazepines (median dosage 333 mg diazepam-equivalent) were able to be stabilised on a low dose of clonazepam after 7–8 days of treatment with flumazenil.[16]

Flumazenil has been tested against placebo in benzodiazepine-dependent subjects. Results showed that typical benzodiazepine withdrawal effects were reversed with few to no symptoms.[17] Flumazenil was also shown to produce significantly fewer withdrawal symptoms than saline in a randomized, placebo-controlled study with benzodiazepine-dependent subjects. Additionally, relapse rates were much lower during subsequent follow-up.[18]

In vitro studies of tissue cultured cell lines have shown that chronic treatment with flumazenil enhanced the benzodiazepine binding site where such receptors have become more numerous and uncoupling/down-regulation of GABAA has been reversed.[19][20][21] After long-term exposure to benzodiazepines, GABAA receptors become down-regulated and uncoupled. Growth of new receptors and recoupling after prolonged flumazenil exposure has also been observed. It is thought this may be due to increased synthesis of receptor proteins.[22]

Flumazenil was found to be more effective than placebo in reducing feelings of hostility and aggression in patients who had been free of benzodiazepines for 4–266 weeks.[23] This may suggest a role for flumazenil in treating protracted benzodiazepine withdrawal symptoms.

Low-dose, slow subcutaneous flumazenil administration is a safe procedure for patients withdrawing from long-term, high-dose benzodiazepine dependency.[24] It has a low risk of seizures even amongst those who have experienced convulsions when previously attempting benzodiazepine withdrawal.[25]

In Italy, the gold standard for treatment of high-dose benzodiazepine dependency is 8–10 days of low-dose, slowly infused flumazenil.[26] One addiction treatment centre in Italy has used flumazenil to treat over 300 patients who were dependent on high doses of benzodiazepines (up to 70 times higher than conventionally prescribed) with physicians being among the clinic's most common patients.[27]

Pharmacology

[edit]
Flumazenil bound at the alpha-gamma interface of an α1β2γ2 GABAA receptor. H-atoms hidden.

Flumazenil, an imidazobenzodiazepine derivative, antagonizes the actions of benzodiazepines on the central nervous system. Flumazenil competitively inhibits the activity at the benzodiazepine recognition site on the GABA/benzodiazepine receptor complex.[28] It also exhibits weak partial agonism of GABAA receptor complexes that contain α6-type monomers; the clinical relevance of this is unknown.[29]

Flumazenil does not antagonize all of the central nervous system effects of drugs affecting GABA-ergic neurons by means other than the benzodiazepine receptor (including ethanol, barbiturates, and most anesthetics) and does not reverse the effects of opioids. It will however antagonize the action of non-benzodiazepine z-drugs, such as zolpidem and zopiclone, because they act via the benzodiazepine site of the GABA receptor[30] - it has been used to successfully treat z-drug overdose.[30][31][32]

Pharmacodynamics

[edit]

Intravenous flumazenil has been shown to antagonize sedation, impairment of recall, psychomotor impairment and ventilatory depression produced by benzodiazepines in healthy human volunteers.

The duration and degree of reversal of sedative benzodiazepine effects are related to the dose and plasma concentrations of flumazenil.

Availability

[edit]

Flumazenil is sold under a wide variety of brand names worldwide like Anexate, Lanexat, Mazicon, Romazicon. In India it is manufactured by Roche Bangladesh Pharmaceuticals and USAN Pharmaceuticals.[citation needed]

See also

[edit]

References

[edit]
  1. ^ "FDA-sourced list of all drugs with black box warnings (Use Download Full Results and View Query links.)". nctr-crs.fda.gov. FDA. Retrieved 22 Oct 2023.
  2. ^ Anvisa (2023-03-31). "RDC Nº 784 - Listas de Substâncias Entorpecentes, Psicotrópicas, Precursoras e Outras sob Controle Especial" [Collegiate Board Resolution No. 784 - Lists of Narcotic, Psychotropic, Precursor, and Other Substances under Special Control] (in Brazilian Portuguese). Diário Oficial da União (published 2023-04-04). Archived from the original on 2023-08-03. Retrieved 2023-08-16.
  3. ^ Hunkeler W, Möhler H, Pieri L, Polc P, Bonetti EP, Cumin R, et al. (April 1981). "Selective antagonists of benzodiazepines". Nature. 290 (5806): 514–516. Bibcode:1981Natur.290..514H. doi:10.1038/290514a0. PMID 6261143. S2CID 4340263.
  4. ^ Whitwam JG, Amrein R (1995-01-01). "Pharmacology of flumazenil". Acta Anaesthesiologica Scandinavica. Supplementum. 108: 3–14. doi:10.1111/j.1399-6576.1995.tb04374.x. PMID 8693922. S2CID 24494744.
  5. ^ Whitwam JG (October 1988). "Flumazenil: a benzodiazepine antagonist". BMJ. 297 (6655): 999–1000. doi:10.1136/bmj.297.6655.999. PMC 1834756. PMID 2903780.
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  16. ^ Quaglio G, Pattaro C, Gerra G, Mathewson S, Verbanck P, Des Jarlais DC, Lugoboni F (August 2012). "High dose benzodiazepine dependence: description of 29 patients treated with flumazenil infusion and stabilised with clonazepam". Psychiatry Research. 198 (3): 457–462. doi:10.1016/j.psychres.2012.02.008. PMID 22424905. S2CID 28979824.
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  19. ^ Pericić D, Lazić J, Strac DS (August 2005). "Chronic treatment with flumazenil enhances binding sites for convulsants at recombinant alpha(1)beta(2)gamma(2S) GABA(A) receptors". Biomedicine & Pharmacotherapy. 59 (7): 408–414. doi:10.1016/j.biopha.2005.02.003. PMID 16084060.
  20. ^ Pericić D, Jazvinsćak Jembrek M, Svob Strac D, Lazić J, Spoljarić IR (January 2005). "Enhancement of benzodiazepine binding sites following chronic treatment with flumazenil". European Journal of Pharmacology. 507 (1–3): 7–13. doi:10.1016/j.ejphar.2004.10.057. PMID 15659288.
  21. ^ Pericić D, Lazić J, Jembrek MJ, Strac DS, Rajcan I (December 2004). "Chronic exposure of cells expressing recombinant GABAA receptors to benzodiazepine antagonist flumazenil enhances the maximum number of benzodiazepine binding sites". Life Sciences. 76 (3): 303–317. doi:10.1016/j.lfs.2004.07.013. PMID 15531382.
  22. ^ Jazvinsćak Jembrek M, Svob Strac D, Vlainić J, Pericić D (July 2008). "The role of transcriptional and translational mechanisms in flumazenil-induced up-regulation of recombinant GABA(A) receptors". Neuroscience Research. 61 (3): 234–241. doi:10.1016/j.neures.2008.03.005. PMID 18453026. S2CID 9033302.
  23. ^ Saxon L, Borg S, Hiltunen AJ (August 2010). "Reduction of aggression during benzodiazepine withdrawal: effects of flumazenil". Pharmacology, Biochemistry, and Behavior. 96 (2): 148–151. doi:10.1016/j.pbb.2010.04.023. PMID 20451546. S2CID 41351863.
  24. ^ Faccini M, Leone R, Opri S, Casari R, Resentera C, Morbioli L, et al. (October 2016). "Slow subcutaneous infusion of flumazenil for the treatment of long-term, high-dose benzodiazepine users: a review of 214 cases". Journal of Psychopharmacology. 30 (10): 1047–1053. doi:10.1177/0269881116647505. PMID 27166362. S2CID 27167585.
  25. ^ Tamburin S, Faccini M, Casari R, Federico A, Morbioli L, Franchini E, et al. (October 2017). "Low risk of seizures with slow flumazenil infusion and routine anticonvulsant prophylaxis for high-dose benzodiazepine dependence". Journal of Psychopharmacology. 31 (10): 1369–1373. doi:10.1177/0269881117714050. PMID 28613124. S2CID 42432213.
  26. ^ Lugoboni F, Faccini M, Quaglio G, Casari R, Albiero A, Pajusco B (April 2011). "Agonist substitution for high-dose benzodiazepine-dependent patients: let us not forget the importance of flumazenil". Addiction. 106 (4): 853. doi:10.1111/j.1360-0443.2010.03327.x. PMID 21320225.
  27. ^ Lugoboni F, Leone R (July 2012). "What is stopping us from using flumazenil?". Addiction. 107 (7): 1359. doi:10.1111/j.1360-0443.2012.03851.x. PMID 22509854.
  28. ^ Hood SD, Norman A, Hince DA, Melichar JK, Hulse GK (February 2014). "Benzodiazepine dependence and its treatment with low dose flumazenil". British Journal of Clinical Pharmacology. 77 (2): 285–294. doi:10.1111/bcp.12023. PMC 4014019. PMID 23126253.
  29. ^ Hadingham KL, Garrett EM, Wafford KA, Bain C, Heavens RP, Sirinathsinghji DJ, Whiting PJ (February 1996). "Cloning of cDNAs encoding the human gamma-aminobutyric acid type A receptor alpha 6 subunit and characterization of the pharmacology of alpha 6-containing receptors". Molecular Pharmacology. 49 (2): 253–259. PMID 8632757.
  30. ^ a b Gunja N (June 2013). "The clinical and forensic toxicology of Z-drugs". Journal of Medical Toxicology. 9 (2): 155–162. doi:10.1007/s13181-013-0292-0. PMC 3657020. PMID 23404347.
  31. ^ Thornton SL, Negus E, Carstairs SD (November 2013). "Pediatric zolpidem ingestion demonstrating zero-order kinetics treated with flumazenil". Pediatric Emergency Care. 29 (11): 1204–1206. doi:10.1097/PEC.0b013e3182aa139c. PMID 24196090. S2CID 34655918.
  32. ^ Lheureux P, Debailleul G, De Witte O, Askenasi R (March 1990). "Zolpidem intoxication mimicking narcotic overdose: response to flumazenil". Human & Experimental Toxicology. 9 (2): 105–107. Bibcode:1990HETox...9..105L. doi:10.1177/096032719000900209. PMID 2111156. S2CID 34525063.
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