| Skeletal muscle relaxants | Chlorzoxazone is an orally active central skeletal muscle relaxant with its chemical structure being completely different with all the other muscle relaxants. It, mainly through acting on the central cerebral cortex and the spinal cord, inhibits the multi-synaptic reflection related to muscle spasms and produces muscle relaxation, further relieves the spasm caused pain and increase the flexibility of the muscles involved. Acetaminophen belongs to non-steroidal anti-inflammatory drugs and may mainly exert the analgesic and antipyretic effects through the inhibition of prostaglandin synthesis. Muscle relaxation studies through mouse traction test have demonstrated that the compound Chlorzoxazone showed a dose-dependent muscle relaxant effect with excellent protective effect on the strychnine-induced seizures in mice. The existence of paracetamol in the compound chlorzoxazone tablets can further enhance the effect of chlorzoxazone. Hot plate analgesic tests have showed the compound chlorzoxazone has a significant analgesic effect in a dose-dependent manner. It also has antagonism effect on the painful writhing of mice caused by antimony potassium tartrate in a good dose-response relationship. Test results have showed that acetaminophen and chlorzoxazone analgesic synergy.
This information is edited by Xiongfeng Dai from Chemicalbook.
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| Pharmacokinetics | This product can be completely absorbed by the digestive tract with the plasma concentration reaching peak at 1.5-2 hours. It is distributed in muscle, kidney, liver, brain and fat. After 6 hours, the drug concentration decreases significantly. Almost all of the goods can subject to in vivo catabolism with the elimination half-life being about 1 hour.
This information is edited by Xiongfeng Dai from Chemicalbook.
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| Indications | Chlorzoxazone is suitable for the treatment of various kinds of acute and chronic soft tissue (muscles, ligaments and fascia) sprain, contusion, muscle pain after exercise, pain caused by muscle strain and the muscle spasms caused by the central nervous system lesions as well as chronic fasciitis.
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| Chlorzoxazone synthesis | Take 2, 5-dichloro-nitrobenzene as raw material; go through hydrolysis, reduction reaction to give 2-amino-4-chloro-phenol, followed by cyclization reaction in hydrochloric acid to obtain the finished product of Chlorzoxazone with the total yield being 84%.
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| Medicine interactions | When this product is used in combination with central inhibitory drugs such as phenothiazines and barbituric acid derivative and monoamine oxidase inhibition drugs, we should reduce the usage amount of this product.
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| Side effects | There may be occasionally mild drowsiness, dizziness, nausea, heart palpitations, weakness, abdominal pain and other reactions. This drug should be discontinued in case of allergic reactions. These adverse reactions are generally mild and may go away automatically or alleviated after stopping using this drug.
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| Uses | It can be used as pharmaceutical intermediates.
It can be used as central muscle relaxants, for being applied to a variety of soft tissue pain caused by chronic sprain, contusion and muscle strain as well as muscle spasms and pain caused by the central nervous system and so on.
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| Category | Toxic substances.
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| Toxicity grading | Highly toxic.
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| Acute toxicity | Oral-rat LD50: 763 mg/kg; Oral-Mouse LD50: 440 mg/kg.
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| Flammability and hazard properties | Thermal decomposition can release nitrogen oxides and chlorides smoke.
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| Storage characteristics | Treasury: ventilated, low temperature and dry; store it separately from food raw materials.
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| Extinguishing agent | Water, carbon dioxide, foam, powder. |
| Description | Chlorzoxazone is a muscle relaxant. It acts by blocking nerve
impulses or pain sensations that are sent to brain. Typically, it
is used together with rest and physical therapy to treat skeletal
muscle conditions such as pain or injury. Chlorzoxazone,
5-chloro-2-benzoxazolione, is synthesized by a heterocyclization
reaction of 2-amino-4-chlorophenol with phosgene.
Skeletal muscle relaxants have conventionally been classified
into one group; however, they are actually a heterogeneous
group of medications commonly used to treat two different
types of underlying conditions – spasticity from upper motor
neuron syndromes and muscular pain or spasms from
peripheral musculoskeletal conditions. Medications classified
as skeletal muscle relaxants are baclofen, carisoprodol,
chlorzoxazone, cyclobenzaprine, dantrolene, metaxalone,
methocarbamol, orphenadrine, and tizanidine. These drugs
may impair mental and/or physical abilities required for
driving vehicles. As a class, skeletal muscle relaxants have
central nervous system (CNS)-related side effects: drowsiness,
dizziness, decreased alertness, blurred vision, and ataxia.
Their use has been associated with a twofold increase in the
risk for motor vehicle crashes. Muscle relaxants are included
in the ‘Beers List’ of potentially inappropriate medications
in older adults. Most muscle relaxants are poorly tolerated by
elderly patients because they cause anticholinergic adverse
effects, sedation, and weakness. Although extremely uncommon,
this compound may yield to idiosyncratic and
unpredictable type of liver toxicity. The concomitant use of
alcohol or other CNS depressants may have an additive effect.
Individuals on chlorzoxazone containing drugs should be
monitored for abnormal liver enzymes (e.g., aspartate transaminase
(AST), alanine transaminase (ALT), alkaline phosphatase,
bilirubin, etc.). |
| Description | Chlorzoxazone is a centrally acting muscle relaxant and activator of small and intermediate conductance calcium-activated potassium channels (EC50s = 87 and 98 μM for KCa2.2 and KCa3.1, respectively). In vivo, chlorzoxazone (10 mg/kg) decreases alcohol but not water intake in a dose-dependent manner and reduces the propensity for rapid initial alcohol intake in rats with intermittent, but not continuous, access to alcohol. Formulations containing chlorzoxazone have been used in the treatment of pain and stiffness caused by muscle spasm. This product is also available as an analytical reference standard . |
| Description | Chlorzoxazone (Item No. 25826) is an analytical reference standard categorized as a skeletal muscle relaxant. This product is intended for analytical forensic applications. This product is also available as a general research tool . |
| Chemical Properties | White to Off-White Solid |
| Originator | Paraflex ,McNeil, US ,1958 |
| Uses | For the relief of discomfort associated with acute painful musculoskeletal conditions. |
| Uses | Muscle relaxant (skeletal) |
| Uses | Chlorzoxazone is a benzoxazolone derivative that causes skeletal muscle relaxation and blocks spasticity in clinical studies. Chlorzoxazone enhances small and intermediate conductance calcium-activated potassium channels (EC50s = 87 and 98 μM for KCa2.2 and KCa3.1, respectively). The cytochrome P450 isoform CYP2E1 converts chlorzoxazone to 6-hydroxy chlorzoxazone . The urinary excretion of this 6-hydroxy metabolite is often used as a probe of CYP2E1 activity in studies of hepatotoxicity. |
| Definition | ChEBI: A member of the class of 1,3-benzoxazoles that is 1,3-benzoxazol-2-ol in which the hydrogen atom at position 5 is substituted by chlorine. A centrally acting muscle relaxant with sedative properties, it is used for the symptomatic treatment of painful mus
le spasm. |
| Manufacturing Process | A solution of 16.9 g (0.1 mol) of 2-amino-5-chlorobenzoxazole in 200 ml of 1
N HCl is refluxed until precipitation is complete. The resulting solid is collected
by filtration, dissolved in 200 ml of 1 N NaOH and the solution extracted with
50 ml of ether. Acidification of the alkaline solution gives a precipitate which is
purified by crystallization from acetone to give 2-hydroxy-5-chlorobenzoxazole
melting at 191° to 191.5°C. |
| Brand name | Paraflex (Ortho-McNeil). |
| Therapeutic Function | Muscle relaxant |
| General Description | Chlorzoxazone is a centrally active muscle relaxant used to treat painful muscle spasms linked to musculoskeletal disorders, such as fibrositis, bursitis, myositis, spondylitis, etc.
Pharmaceutical secondary standard for application in quality control. Provides pharma laboratories and manufacturers with a convenient and cost-effective alternative to the preparation of in-house working standards. |
| Biochem/physiol Actions | Chlorzoxazone is a skeletal muscle relaxant. |
| Synthesis | Chlorzoxazone, 5-chloro-2-benzoxazolione (15.3.15), is synthesized by
a hetercyclization reaction of 2-amino-4-chlorphenol with phosgene. 
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| Environmental Fate | Chlorzoxazone ismetabolized by the CYP1A2 and CYP2E1 microsomal
enzymes to a toxic metabolite 6-hydroxychlorzoxazone. |
| Toxicity evaluation | Chlorzoxazone is a white to off-white solid. It is soluble in organic solvents
such as ethanol, methanol, and dimethyl sulfoxide (DMSO). |
