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2D Structure
Also known as: 95-25-0, Paraflex, Chloroxazone, Chlorzoxazon, 5-chloro-2-benzoxazolone, 5-chloro-2-benzoxazolinone
Molecular Formula
C7H4ClNO2
Molecular Weight
169.56  g/mol
InChI Key
TZFWDZFKRBELIQ-UHFFFAOYSA-N
FDA UNII
H0DE420U8G

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)
Chlorzoxazone is a Muscle Relaxant. The physiologic effect of chlorzoxazone is by means of Centrally-mediated Muscle Relaxation.
1 2D Structure

2D Structure

2 Identification
2.1 Computed Descriptors
2.1.1 IUPAC Name
5-chloro-3H-1,3-benzoxazol-2-one
2.1.2 InChI
InChI=1S/C7H4ClNO2/c8-4-1-2-6-5(3-4)9-7(10)11-6/h1-3H,(H,9,10)
2.1.3 InChI Key
TZFWDZFKRBELIQ-UHFFFAOYSA-N
2.1.4 Canonical SMILES
C1=CC2=C(C=C1Cl)NC(=O)O2
2.2 Other Identifiers
2.2.1 UNII
H0DE420U8G
2.3 Synonyms
2.3.1 MeSH Synonyms

1. Paraflex

2. Parafon

3. Parafon Forte Dsc

2.3.2 Depositor-Supplied Synonyms

1. 95-25-0

2. Paraflex

3. Chloroxazone

4. Chlorzoxazon

5. 5-chloro-2-benzoxazolone

6. 5-chloro-2-benzoxazolinone

7. 2(3h)-benzoxazolone, 5-chloro-

8. Biomioran

9. Escoflex

10. Myoflexin

11. Myoflexine

12. Pathorysin

13. 5-chloro-2-hydroxybenzoxazole

14. Mioran

15. Miotran

16. Neoflex

17. Solaxin

18. 5-chloro-2(3h)-benzoxazolone

19. Parafon Forte Dsc

20. 5-chlorobenzoxazolidone

21. 5-chlorobenzo[d]oxazol-2(3h)-one

22. 5-chloro-2-benzoxazolol

23. Chlorzoxane

24. 5-chloro-1,3-benzoxazol-2(3h)-one

25. Usaf Ma-10

26. 5-chlorobenzoxazol-2-one

27. 5-chloro-3h-1,3-benzoxazol-2-one

28. Strifon Forte Dsc

29. Parafon

30. 5-chlorobenzoxazolone

31. 2-hydroxy-5-chlorobenzoxazole

32. Chlorzoxazonum

33. 5-chlorbenzoxazolin-2-on

34. 5-chloro-3(h)-2-benzoxazolone

35. 5-chlorobenzo[d]oxazol-2-ol

36. 5-chlorobenzoksazolon-2

37. 5-chlorobenzoksazolinon-2

38. 5-chlorobenzoxazolin-2-one

39. Strifon

40. Nsc 26189

41. 2-benzoxazolinone, 5-chloro-

42. 5-chloro-3h-benzooxazol-2-one

43. 5-chloro-1,3-benzoxazol-2-ol

44. Chembl1371

45. Mls000069380

46. Chebi:3655

47. H0de420u8g

48. Chlorsoxazone

49. Klorzoxazon

50. Nyoflex

51. Remofleks

52. 5-chloro-2,3-dihydro-1,3-benzoxazol-2-one

53. Parafon Forte

54. Nsc-26189

55. Cas-95-25-0

56. Ncgc00015238-02

57. Clorzoxazona

58. Lorzone

59. Smr000058269

60. Dsstox_cid_2813

61. Dsstox_rid_76739

62. Dsstox_gsid_22813

63. Clw

64. Chlorzoxazonum [inn-latin]

65. Clorzoxazona [inn-spanish]

66. Chlorzoxazona

67. 5-chlorobenzoksazolon-2 [polish]

68. 5-chlorobenzoksazolinon-2 [polish]

69. Paraflex (tn)

70. Sr-01000075207

71. Einecs 202-403-9

72. Mfcd00005717

73. Component Of Parafon Forte

74. Unii-h0de420u8g

75. Ai3-63119

76. Chlorzoxazone (jan/usp/inn)

77. Prestwick_62

78. Chlorzoxazone,(s)

79. Chlorzoxazone [usp:inn:ban:jan]

80. 5-chlorobenzoxazolinone

81. Spectrum_000148

82. Opera_id_1659

83. Prestwick0_000163

84. Prestwick1_000163

85. Prestwick2_000163

86. Prestwick3_000163

87. Spectrum2_001149

88. Spectrum3_000350

89. Spectrum4_000287

90. Spectrum5_000745

91. Lopac-c-4397

92. Chlorzoxazone [mi]

93. C 4397

94. Chlorzoxazone [inn]

95. Chlorzoxazone [jan]

96. 5-chloro-benzooxazol-2-ol

97. 5-chloro-benzoxazolin-2-one

98. Lopac0_000253

99. Schembl35177

100. Bspbio_000025

101. Bspbio_002019

102. Chlorzoxazone [vandf]

103. Kbiogr_000814

104. Kbioss_000628

105. Wln: T56 Bmvoj Hg

106. Chlorzoxazone [mart.]

107. Divk1c_000895

108. Spectrum1500188

109. Spbio_001077

110. Spbio_001946

111. Chlorzoxazone [usp-rs]

112. Chlorzoxazone [who-dd]

113. Bpbio1_000029

114. Gtpl2322

115. Dtxsid9022813

116. Hms502m17

117. Kbio1_000895

118. Kbio2_000628

119. Kbio2_003196

120. Kbio2_005764

121. Kbio3_001239

122. Ninds_000895

123. Chlorzoxazone-[13c,15n,18o]

124. Hms1568b07

125. Hms1920o07

126. Hms2091e14

127. Hms2095b07

128. Hms2235i19

129. Hms3259i15

130. Hms3260d08

131. Hms3373p17

132. Hms3652k22

133. Hms3712b07

134. Hms3885n07

135. Pharmakon1600-01500188

136. 5-chloro-2-hydroxybenzo[d]oxazole

137. Chlorzoxazone [orange Book]

138. Act08248

139. Albb-012641

140. Bcp07916

141. Hy-b1462

142. Nsc26189

143. Str00805

144. Chlorzoxazone [usp Impurity]

145. Tox21_110105

146. Tox21_500253

147. Bdbm50290811

148. Ccg-40323

149. Chlorzoxazone [usp Monograph]

150. Nsc756693

151. S4155

152. Stk071582

153. Zinc84843283

154. Akos000404381

155. Tox21_110105_1

156. Component Of Parafon Forte (salt/mix)

157. Cs-5155

158. Db00356

159. Hg-0202

160. Lp00253

161. Nc00499

162. Nsc-756693

163. Sdccgsbi-0050241.p005

164. 5-chloranyl-3h-1,3-benzoxazol-2-one

165. 5-chloro-1,3-benzoxazole-2(3h)-one

166. Idi1_000895

167. Chlorzoxazone 1.0 Mg/ml In Acetonitrile

168. Ncgc00015238-01

169. Ncgc00015238-03

170. Ncgc00015238-04

171. Ncgc00015238-05

172. Ncgc00015238-06

173. Ncgc00015238-07

174. Ncgc00015238-08

175. Ncgc00015238-09

176. Ncgc00015238-10

177. Ncgc00015238-13

178. Ncgc00015238-24

179. Ncgc00093714-01

180. Ncgc00093714-02

181. Ncgc00093714-03

182. Ncgc00093714-04

183. Ncgc00260938-01

184. 5-chloro-1,3-benzoxazol-2(3h)-one #

185. Ac-12192

186. Bp-11613

187. Meso-butane-1,2,3,4-tetracarboxylicacid

188. Sbi-0050241.p004

189. Db-057571

190. Ab00051947

191. Eu-0100253

192. Ft-0620220

193. Sw196377-3

194. En300-31026

195. A16449

196. C07931

197. D00771

198. D78096

199. Ab00051947_05

200. Ab00051947_06

201. A845253

202. Q3294630

203. Sr-01000075207-1

204. Sr-01000075207-3

205. Sr-01000075207-5

206. W-100168

207. Brd-k98174813-001-05-7

208. Brd-k98174813-001-08-1

209. Z57183224

210. Chlorzoxazone, United States Pharmacopeia (usp) Reference Standard

2.4 Create Date
2005-03-25
3 Chemical and Physical Properties
Molecular Weight 169.56 g/mol
Molecular Formula C7H4ClNO2
XLogP31.8
Hydrogen Bond Donor Count1
Hydrogen Bond Acceptor Count2
Rotatable Bond Count0
Exact Mass168.9930561 g/mol
Monoisotopic Mass168.9930561 g/mol
Topological Polar Surface Area38.3 Ų
Heavy Atom Count11
Formal Charge0
Complexity185
Isotope Atom Count0
Defined Atom Stereocenter Count0
Undefined Atom Stereocenter Count0
Defined Bond Stereocenter Count0
Undefined Bond Stereocenter Count0
Covalently Bonded Unit Count1
4 Drug and Medication Information
4.1 Drug Information
1 of 4  
Drug NameChlorzoxazone
PubMed HealthChlorzoxazone (By mouth)
Drug ClassesSkeletal Muscle Relaxant, Centrally Acting
Drug LabelChlorzoxazone USP is a centrally acting skeletal muscle relaxant, available as tablets of 500 mg for oral administration. Its chemical name is 5-Chloro-2-benzoxazolinone, and its structural formula is: Chlorzoxazone Structural FormulaC7H4CINO2 MW 1...
Active IngredientChlorzoxazone
Dosage FormTablet
RouteOral
Strength750mg; 375mg; 500mg
Market StatusPrescription
CompanyWatson Labs; Mikart; Barr

2 of 4  
Drug NameParafon forte dsc
PubMed HealthChlorzoxazone (By mouth)
Drug ClassesSkeletal Muscle Relaxant, Centrally Acting
Drug LabelEach caplet (capsule shaped tablet) contains:*5-chlorobenzoxazolinoneChlorzoxazone*500 mgInactive ingredients: FD&C Blue No. 1, microcrystalline cellulose, docusate sodium, lactose (hydrous), magnesium stearate, sodium benzoate, sodium star...
Active IngredientChlorzoxazone
Dosage FormTablet
RouteOral
Strength500mg
Market StatusPrescription
CompanyJanssen R And D

3 of 4  
Drug NameChlorzoxazone
PubMed HealthChlorzoxazone (By mouth)
Drug ClassesSkeletal Muscle Relaxant, Centrally Acting
Drug LabelChlorzoxazone USP is a centrally acting skeletal muscle relaxant, available as tablets of 500 mg for oral administration. Its chemical name is 5-Chloro-2-benzoxazolinone, and its structural formula is: Chlorzoxazone Structural FormulaC7H4CINO2 MW 1...
Active IngredientChlorzoxazone
Dosage FormTablet
RouteOral
Strength750mg; 375mg; 500mg
Market StatusPrescription
CompanyWatson Labs; Mikart; Barr

4 of 4  
Drug NameParafon forte dsc
PubMed HealthChlorzoxazone (By mouth)
Drug ClassesSkeletal Muscle Relaxant, Centrally Acting
Drug LabelEach caplet (capsule shaped tablet) contains:*5-chlorobenzoxazolinoneChlorzoxazone*500 mgInactive ingredients: FD&C Blue No. 1, microcrystalline cellulose, docusate sodium, lactose (hydrous), magnesium stearate, sodium benzoate, sodium star...
Active IngredientChlorzoxazone
Dosage FormTablet
RouteOral
Strength500mg
Market StatusPrescription
CompanyJanssen R And D

4.2 Drug Indication

For the relief of discomfort associated with acute painful musculoskeletal conditions.


5 Pharmacology and Biochemistry
5.1 Pharmacology

Chlorzoxazone is a centrally-acting agent for painful musculoskeletal conditions. Data available from animal experiments as well as human study indicate that chlorzoxazone acts primarily at the level of the spinal cord and subcortical areas of the brain where it inhibits multisynaptic reflex a.c. involved in producing and maintaining skeletal muscle spasm of varied etiology. The clinical result is a reduction of the skeletal muscle spasm with relief of pain and increased mobility of the involved muscles.


5.2 MeSH Pharmacological Classification

Muscle Relaxants, Central

A heterogeneous group of drugs used to produce muscle relaxation, excepting the neuromuscular blocking agents. They have their primary clinical and therapeutic uses in the treatment of muscle spasm and immobility associated with strains, sprains, and injuries of the back and, to a lesser degree, injuries to the neck. They have been used also for the treatment of a variety of clinical conditions that have in common only the presence of skeletal muscle hyperactivity, for example, the muscle spasms that can occur in MULTIPLE SCLEROSIS. (From Smith and Reynard, Textbook of Pharmacology, 1991, p358) (See all compounds classified as Muscle Relaxants, Central.)


5.3 FDA Pharmacological Classification
5.3.1 Active Moiety
CHLORZOXAZONE
5.3.2 FDA UNII
H0DE420U8G
5.3.3 Pharmacological Classes
Muscle Relaxant [EPC]; Centrally-mediated Muscle Relaxation [PE]
5.4 ATC Code

M - Musculo-skeletal system

M03 - Muscle relaxants

M03B - Muscle relaxants, centrally acting agents

M03BB - Oxazol, thiazine, and triazine derivatives

M03BB03 - Chlorzoxazone


5.5 Absorption, Distribution and Excretion

Route of Elimination

Chlorzoxazone is rapidly metabolized and is excreted in the urine, primarily in a conjugated form as the glucuronide.


5.6 Metabolism/Metabolites

Chlorzoxazone is rapidly metabolized in the liver and is excreted in the urine, primarily in a conjugated form as the glucuronide.


Chlorzoxazone has known human metabolites that include 6-Hydroxychlorzoxazone.

S73 | METXBIODB | Metabolite Reaction Database from BioTransformer | DOI:10.5281/zenodo.4056560


5.7 Mechanism of Action

Chlorzoxazone inhibits degranulation of mast cells, subsequently preventing the release of histamine and slow-reacting substance of anaphylaxis (SRS-A), mediators of type I allergic reactions. Chlorzoxazone also may reduce the release of inflammatory leukotrienes. Chlorzoxazone may act by inhibiting calcium and potassium influx which would lead to neuronal inhibition and muscle relaxation. Data available from animal experiments as well as human study indicate that chlorzoxazone acts primarily at the level of the spinal cord and subcortical areas of the brain where it inhibits multisynaptic reflex arcs involved in producing and maintaining skeletal muscle spasm