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Chlorzoxazone

Clinical data
Trade names	Lorzone, Paraflex, Muscol
AHFS/Drugs.com	Monograph
MedlinePlus	a682577
License data	US DailyMed: Chlorzoxazone
Routes of administration	By mouth
Drug class	Skeletal muscle relaxants
ATC code	M03BB03 (WHO)
Legal status
Legal status	US: ℞-only
Pharmacokinetic data
Bioavailability	Well absorbed
Protein binding	13–18%
Metabolism	Hepatic
Elimination half-life	1.1 hours
Duration of action	3–4 hours
Excretion	urine (<1%)
Identifiers
IUPAC name 5-chloro-3H-benzooxazol-2-one
CAS Number	95-25-0
PubChem CID	2733
IUPHAR/BPS	2322
DrugBank	DB00356
ChemSpider	2632
UNII	H0DE420U8G
KEGG	D00771
ChEBI	CHEBI:3655
ChEMBL	ChEMBL1371
CompTox Dashboard (EPA)	DTXSID9022813
ECHA InfoCard	100.002.186
Chemical and physical data
Formula	C7H4ClNO2
Molar mass	169.56 g·mol
3D model (JSmol)	Interactive image
SMILES Clc2cc1c(OC(=O)N1)cc2
InChI InChI=1S/C7H4ClNO2/c8-4-1-2-6-5(3-4)9-7(10)11-6/h1-3H,(H,9,10) Key:TZFWDZFKRBELIQ-UHFFFAOYSA-N
(verify)

Chlorzoxazone (INN) is a centrally acting muscle relaxant used to treat muscle spasm and the resulting pain or discomfort. It can also be administered for acute pain in general and for tension headache (muscle contraction headache). It acts on the spinal cord by depressing reflexes. It is sold under the brand names Lorzone, Paraflex and Muscol and in combination form as Parafon Forte, a combination of chlorzoxazone and acetaminophen (paracetamol). Possible side effects include dizziness, lightheadedness, malaise, nausea, vomiting. In rare cases, chlorzoxazone may cause severe liver dysfunction. On the other hand, chlorzoxazone may reduce the liver toxicity of acetaminophen by competitive inhibition.

It is available as a generic medication.

Like metaxalone, its mechanism of action is still in question. It is believed that metaxalone works by altering serotonin levels and acting as a mild MAO inhibitor. The mechanism of action of chlorzoxazone is thought to act on GABA_A and GABA_B receptors and voltage-gated calcium channels to a degree. General central nervous system depression is the only currently accepted aspect to its medical benefits. Elucidation of the exact mechanism of action is ongoing but there is limited study due to the existence of more effective, safe muscle relaxants (e.g., diazepam, cyclobenzaprine, tizanidine), greatly limiting the potential benefit of identifying novel compounds which share chlorzoxazone's mechanism of action.

See also

• Zoxazolamine

References

1. "Parafon DSC- chlorzoxazone tablet". DailyMed. 9 February 2010. Retrieved 5 November 2020.
2. "Lorzone- chlorzoxazone tablet". DailyMed. 21 June 2019. Retrieved 5 November 2020.
3. "Chlorzoxazone". LiverTox. National Institute of Diabetes and Digestive and Kidney Diseases. 2017-01-30. PMID 31643467. Retrieved 2024-05-10.
4. Pingili RB, Vemulapalli S, Gadamsetty MV, Presingu D, Katuri R, Rachamsetty V, et al. (2023-04-17). "Chlorzoxazone reduced the paracetamol-induced toxicity via competitive inhibition of CYP2E1-mediated metabolism". Future Journal of Pharmaceutical Sciences. 9 (1). doi:10.1186/s43094-023-00484-2. ISSN 2314-7253.
5. "Competitive Generic Therapy Approvals". U.S. Food and Drug Administration (FDA). 29 June 2023. Archived from the original on 29 June 2023. Retrieved 29 June 2023.

Further reading

• Dong DL, Luan Y, Feng TM, Fan CL, Yue P, Sun ZJ, et al. (September 2006). "Chlorzoxazone inhibits contraction of rat thoracic aorta". European Journal of Pharmacology. 545 (2–3): 161–166. doi:10.1016/j.ejphar.2006.06.063. PMID 16859676.
• Park JY, Kim KA, Park PW, Ha JM (January 2006). "Effect of high-dose aspirin on CYP2E1 activity in healthy subjects measured using chlorzoxazone as a probe". Journal of Clinical Pharmacology. 46 (1): 109–114. doi:10.1177/0091270005282635. PMID 16397290. S2CID 20092326.
• Wan J, Ernstgård L, Song BJ, Shoaf SE (January 2006). "Chlorzoxazone metabolism is increased in fasted Sprague-Dawley rats". The Journal of Pharmacy and Pharmacology. 58 (1): 51–61. doi:10.1211/jpp.58.1.0007. PMC 1388188. PMID 16393464.

External links

• "Chlorzoxazone". Drug Information Portal. U.S. National Library of Medicine.
• Chloroxazone Safety Data Sheet Archived 2019-07-12 at the Wayback Machine
• D.F. Marsh, U.S. patent 2,895,877 (1959)

• Medicine

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