Chlorzoxazone

Chlorzoxazone is a Skeletal Muscle Relaxant belonging to the analgesic class.

Chlorzoxazone is a drug with muscle relaxant properties that is used as an adjunct to physical therapy and analgesics to treat stiffness and pain caused by a variety of musculoskeletal conditions.

Chlorzoxazone is Rapidly and completely absorbed from the GI tract. Time taken to reach peak plasma concentration is Approximately 1-2 hours. The duration of action of Chlorzoxazone is up to 6 hours. Chlorzoxazone is rapidly metabolized in the liver by CYP2E1 enzyme via glucuronidation to an inactive metabolite, 6-hydroxychlorzoxazone. Chlorzoxazone excreted via urine (mainly as glucuronide metabolite, <1% as unchanged drug).

Chlorzoxazone shows side effects like Bloody stool, Constipation, Cough, Dark urine, Dizziness, Nausea and Vomiting, Drowsiness, Rash, Weakness, Stomach pain, Shortness of breath, Tightness of chest.

Chlorzoxazone is available in the form of Oral tablets.

Chlorzoxazone is available in India, US, Canada, Mexico, UK, China, Brazil, Germany, Japan, Australia and Malaysia.

Chlorzoxazone is an Analgesic belonging to the class Skeletal Muscle Relaxant.

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.

The Onset of action of Chlorzoxazone can be observed within 1 hour of administration of the dose.

The amount of time for which Chlorzoxazone remains active in the body is about 3 to 4 hours.

The time to peak concentration of Chlorzoxazone is approximately 1 to 2 hours.

Chlorzoxazone is available in the form of Oral tablets.

Chlorzoxazone tablet is taken orally, usually 3 or 4 times daily.

Chlorzoxazone is a muscle relaxant which is used to relieve stiffness and pain caused by muscle sprains and strains. Chlorzoxazone should be used in combination with rest and physical therapy to obtain the best possible effect.

Chlorzoxazone is a Skeletal Muscle Relaxant belonging to the analgesic class.

Chlorzoxazone centrally acting agent; acts on the spinal cord and subcortical areas of the brain to inhibit polysynaptic reflex arcs involved in causing and maintaining skeletal muscle spasms.

Chlorzoxazone is approved for use in the following clinical indications

• Musculoskeletal conditions

Chlorzoxazone is a drug with muscle relaxant properties that is used as an adjunct to physical therapy and analgesics to treat stiffness and pain caused by a variety of musculoskeletal conditions.

• Musculoskeletal conditions

Adult Oral: 250 to 500 mg 3 or 4 times daily; for painful musculoskeletal conditions, may initiate therapy with 500 mg 3 or 4 times daily. May increase dose based on response and tolerability to 750 mg 3 or 4 times daily.

Children and Adolescents Dose: 20 mg/kg/day in 3 to 4 divided doses; dosing based on generally recognized expert recommendations; published pediatric trial data is lacking; in reported experience, initial dose range: 125 to 250 mg 3 times daily.

Chlorzoxazone is available in various strengths as 250 mg; 500 mg; 750 mg; 375 mg.

Chlorzoxazone is available in the form of Oral Tablet.

Chlorzoxazone is contraindicated in patients with

• Hypersensitivity to chlorzoxazone or any component of the formulation.

• CNS depression: May cause CNS depression, which may impair physical or mental abilities; patients must be cautioned about performing tasks that require mental alertness (eg, operating machinery or driving).

• Hepatotoxicity: Rare, serious (including fatal) idiosyncratic and unpredictable hepatocellular toxicity has been reported with use. Discontinue immediately if early signs/symptoms of hepatic toxicity arise (eg, fever, rash, anorexia, nausea, vomiting, fatigue, right upper quadrant pain, dark urine, jaundice). Also discontinue if elevated liver enzymes (eg, AST, ALT, alkaline phosphatase, bilirubin) develop.

• Hypersensitivity reaction: Use caution in patients with known allergies or a history of allergic reactions to drugs; if sensitivity (itching, redness, urticaria) occurs, discontinue therapy.

Use of alcohol is not recommended during treatment with this medicine due to the increased risk of nervous system side effects such as dizziness, drowsiness, and difficulty concentrating.

Chlorzoxazone is not recommended for use in breastfeeding women unless absolutely necessary. All the risks and benefits should be considered before taking Chlorzoxazone.

Chlorzoxazone is not recommended for use in pregnant women unless necessary. Before taking Chlorzoxazone, the risks and benefits should be considered.

• Common

Elevated liver enzymes (i.e. ALT, AST, bilirubin, alkaline, phosphatase), Drowsiness, dizziness, headache, light-headedness, malaise, overstimulation, Anorexia, nausea, vomiting, heartburn, abdominal distress, constipation, diarrhea. Jaundice, Urine discolouration, Rashes, petechiae, ecchymosis, urticaria, pruritus, Rarely, hepatocellular toxicity.

Chlormethiazole: May enhance the CNS depressant effect of Chlorzoxazone. Chlormethiazole may increase the serum concentration of Chlorzoxazone. Management: Consider reduced doses of chlorzoxazone when combined with chlormethiazole. Monitor patients for increased chlorzoxazone effects/toxicities (ie, CNS depression, sedation) if these agents are combined.

Daridorexant: May enhance the CNS depressant effect of CNS Depressants. Management: Dose reduction of daridorexant and/or any other CNS depressant may be necessary. Use of daridorexant with alcohol is not recommended, and the use of daridorexant with any other drug to treat insomnia is not recommended.

Doxylamine: May enhance the CNS depressant effect of CNS Depressants. Management: The manufacturer of Diclegis (doxylamine/pyridoxine), intended for use in pregnancy, specifically states that use with other CNS depressants is not recommended.

Flunitrazepam: CNS Depressants may enhance the CNS depressant effect of Flunitrazepam. Management: Reduce the dose of CNS depressants when combined with flunitrazepam and monitor patients for evidence of CNS depression (eg, sedation, respiratory depression). Use non-CNS depressant alternatives when available.

Lemborexant: May enhance the CNS depressant effect of CNS Depressants. Management: Dosage adjustments of lemborexant and of concomitant CNS depressants may be necessary when administered together because of potentially additive CNS depressant effects. Close monitoring for CNS depressant effects is necessary.

Methotrimeprazine: May enhance the CNS depressant effect of CNS Depressants. CNS Depressants may enhance the CNS depressant effect of Methotrimeprazine. Management: Reduce the usual dose of CNS depressants by 50% if starting methotrimeprazine until the dose of methotrimeprazine is stable. Monitor patient closely for evidence of CNS depression.

Opioid Agonists: CNS Depressants may enhance the CNS depressant effect of Opioid Agonists. Management: Avoid concomitant use of opioid agonists and benzodiazepines or other CNS depressants when possible. These agents should only be combined if alternative treatment options are inadequate. If combined, limit the dosages and duration of each drug.

Oxybate Salt Products: CNS Depressants may enhance the CNS depressant effect of Oxybate Salt Products. Management: Consider alternatives to this combination when possible. If combined, dose reduction or discontinuation of one or more CNS depressants (including the oxybate salt product) should be considered. Interrupt oxybate salt treatment during short-term opioid use.

Suvorexant: CNS Depressants may enhance the CNS depressant effect of Suvorexant. Management: Dose reduction of suvorexant and/or any other CNS depressant may be necessary. Use of suvorexant with alcohol is not recommended, and the use of suvorexant with any other drug to treat insomnia is not recommended.

Zolpidem: CNS Depressants may enhance the CNS depressant effect of Zolpidem. Management: Reduce the Intermezzo brand sublingual zolpidem adult dose to 1.75 mg for men who are also receiving other CNS depressants. No such dose change is recommended for women. Avoid use with other CNS depressants at bedtime; avoid use with alcohol.

The common side effects of Chlorzoxazone include the following

• Common side effects

Upset stomach, drowsiness, dizziness, light-headedness, weakness.

• Rare side effects

Skin rash or itching, yellowing of the skin or eyes, stomach pain.

• Pregnancy

Pregnancy Category C

Chlorzoxazone is not recommended for use in pregnant women unless necessary. Before taking Chlorzoxazone, the risks and benefits should be considered.

• Nursing Mothers

Chlorzoxazone is not recommended for use in breastfeeding women unless necessary. All the risks and benefits should be considered before taking Chlorzoxazone.

Symptoms: Nausea, vomiting, diarrhea, dizziness, drowsiness, headache, light-headedness, malaise, sluggishness, loss of muscle tone, decreased or absent deep tendon reflexes, hypotension, resp depression.

Management: Supportive treatment. Employ gastric lavage or induce emesis, followed by admin of activated charcoal. Maintain adequate airway, assisted respiration, and may treat hypotension w/ cautious admin of vasopressor agent (e.g. norepinephrine), if necessary.

• Pharmacodynamic

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.

• Pharmacokinetics

Absorption

Chlorzoxazone is Rapidly and completely absorbed from the GI tract. Time taken to reach peak plasma concentration is Approximately 1-2 hours.

Distribution

The duration of action of Chlorzoxazone up to 6 hours.

Metabolism and Excretion

Chlorzoxazone is rapidly metabolized in the liver by CYP2E1 enzyme via glucuronidation to an inactive metabolite, 6-hydroxychlorzoxazone. Chlorzoxazone excreted via urine (mainly as glucuronide metabolite, <1% as unchanged drug).

• https://www.rxlist.com/chlorzoxazone-drug.htm
• https://www.uptodate.com/contents/chlorzoxazone-drug-information#F52812490
• https://medlineplus.gov/druginfo/meds/a682577.html#:~:text=Chlorzoxazone is used to relieve,or acetaminophen), and rest.
• https://www.drugs.com/pregnancy/chlorzoxazone.html
• https://go.drugbank.com/drugs/DB00356