Chlorzoxazone
Verifiedrevid458941862
TradenameLorzone, Paraflex, Muscol
Medlineplusa682577
DailymedidChlorzoxazone
Pregnancy usN
Routes of administrationBy mouth
Atc prefixM03
Atc suffixBB03
ClassSkeletal muscle relaxants
Legal usRx-only
Legal us comment[1][2]
BioavailabilityWell absorbed
Protein bound13–18%
MetabolismHepatic
Elimination half-life1.1 hours
Duration of action3–4 hours
Excretionurine (<1%)
Cas number95-25-0
Pubchem2733
Iuphar ligand2322
DrugbankDB00356
Chemspiderid2632
UniiH0DE420U8G
KeggD00771
Chebi3655
Chembl1371
Iupac name5-chloro-3H-benzooxazol-2-one
C7
H4
Cl1
N1
O2
SmilesClc2cc1c(OC(=O)N1)cc2
Stdinchi1S/C7H4ClNO2/c8-4-1-2-6-5(3-4)9-7(10)11-6/h1-3H,(H,9,10)
StdinchikeyTZFWDZFKRBELIQ-UHFFFAOYSA-N

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.[3] Conversely, chlorzoxazone may reduce the liver toxicity of acetaminophen by competitive inhibition.[4]

It is available as a generic medication.[5]

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[by whom?] to act on GABAA and GABAB 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

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, Kilaru NB (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 29 June 2023 at the Wayback Machine. Retrieved 29 June 2023.

Further reading

  • Dong DL, Luan Y, Feng TM, Fan CL, Yue P, Sun ZJ, Gu RM, Yang BF (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