|Chlorzoxazone; Paraflex; Chlorzoxazon; Myoflexin; Solaxin; 95-25-0;|
A centrally acting central muscle relaxant with sedative properties. It is claimed to inhibit muscle spasm by exerting an effect primarily at the level of the spinal cord and subcortical areas of the brain. (From Martindale, The Extra Pharmacopoea, 30th ed, p1202)
|melting point||191-191.5||Marsh, D.F.; US. Patent 2,895,877; July 21, 1959; assigned to McNeil Laboratories, Inc.|
Marsh, D.F.; US. Patent 2,895,877; July 21, 1959; assigned to McNeil Laboratories, Inc.
Chlorzoxazone (Paraflex) is a centrally acting muscle relaxant used to treat muscle spasm and the resulting pain or discomfort. It acts on the spinal cord by depressing reflexes. It is sold as Muscol or Parafon Forte, a combination of chlorzoxazone and acetaminophen (Paracetamol). Possible side effects include dizziness, lightheadedness, malaise, nausea, vomiting, and liver dysfunction. Used with acetaminophen it has added risk of hepatoxicity, which is why the combination is not recommended. It can also be administered for acute pain in general and for tension headache (muscle contraction headache).
Chlorzoxazone, 5-chloro-2-benzoxazolione, is synthesized by a hetercyclization reaction of 2-amino-4-chlorophenol with phosgene.
The Chlorzoxazone with CAS registry number of 95-25-0 is also known as 2-Benzoxazolol, 5-chloro-. The IUPAC name is 5-Chloro-3H-1,3-benzoxazol-2-one. It belongs to product categories of Oxazole&Isoxazole; Intermediates & Fine Chemicals; Pharmaceuticals. Its EINECS registry number is 202-403-9. In addition, the formula is C7H4ClNO2 and the molecular weight is 169.57. This chemical should be stored in sealed containers in cool, dry place and away from oxidizing agents.
Physical properties about Chlorzoxazone are: (1)ACD/LogP: 2.19; (2)# of Rule of 5 Violations: 0; (3)ACD/LogD (pH 5.5): 2.19; (4)ACD/LogD (pH 7.4): 2.15; (5)ACD/BCF (pH 5.5): 27.16; (6)AACD/KOC (pH 7.4): 340.79; (7)#H bond acceptors: 3; (8)#H bond donors: 1; (9)#Freely Rotating Bonds: 0; (10)Index of Refraction: 1.603; (11)Molar Refractivity: 39.18 cm3; (12)Molar Volume: 114 cm3; (13)Surface Tension: 50 dyne/cm; (14)Density: 1.486 g/cm3; (15)Flash Point: 157.5 °C; (16)Enthalpy of Vaporization: 60.3 kJ/mol; (17)Boiling Point: 336.9 °C at 760 mmHg; (18)Vapour Pressure: 5.58E-05 mmHg at 25 °C.
Preparation of Chlorzoxazone: it is prepared by reaction of 5-chloro-2-hydroxy-benzamide. The reaction needs reagents iodobenzene diacetate, KOH and solvent methanol at the temperature of 0 °C. The yield is about 68%.
- D.F. Marsh, U.S. Patent 2,895,877 (1959).
- Dong DL, Luan Y, Feng TM, Fan CL, Yue P, Sun ZJ, Gu RM, Yang BF. (2006). “Chlorzoxazone inhibit contraction of rat thoracic aorta”. Eur J Pharmacol 545 (2–3): 161–6. doi:10.1016/j.ejphar.2006.06.063. PMID 16859676.
- Park J, Kim K, Park P, Ha J (2006). “Effect of high-dose aspirin on CYP2E1 activity in healthy subjects measured using chlorzoxazone as a probe”. J Clin Pharmacol 46 (1): 109–14. doi:10.1177/0091270005282635. PMID 16397290.
- Wan J, Ernstgård L, Song B, Shoaf S (2006). “Chlorzoxazone metabolism is increased in fasted Sprague-Dawley rats”. J Pharm Pharmacol 58 (1): 51–61. doi:10.1211/jpp.58.1.0007. PMC 1388188. PMID 16393464.
- PARAFON DSC (chlorzoxazone) tablet, Daily Med, U.S. National Library of Medicine
|Systematic (IUPAC) name|
|Biological half-life||1.1 hr|
|CAS Registry Number|
|Molecular mass||169.565 g/mol|