Last Updated December 20th, 2021

Therapeutic Indications

Myospaz is a muscle relaxer and used to treat the pain of muscles and skeletal disorders that are acute. It is a combination medication containing paracetamol and chlorzoxazone. Myospaz is used for management of the following conditions:

  • Muscle spasms
  • A toothache
  • Muscle pain
  • Menstruation pain
  • Fever
  • Headache
  • Backache
  • Muscle sprains and strains due to stiffness
  • Ear pain
  • Cold
  • Flu
  • Rheumatoid arthritis
  • Osteoarthritis
  • Spondylitis
  • Arthralgia
  • Cramping
  • Post-operation pain
  • Post-immunization pyrexia.
  • Pain after immunization.
  • Migraine

Do I Need a Prescription?

Myospaz can be bought from pharmacies close to you and from online drug stores. But a doctor’s prescription is mandatory.


The dose for Myospaz depends on the condition being treated, the age, weight, and response to the medication. The recommended dosage for Myospaz is 1 tablet taken two or three times a day.

Chemical Composition

Myospaz contains two active ingredients, these are:

  • 250 mg Chlorzoxazone
  • 325 mg Paracetamol

Paracetamol is also called Acetaminophen.

Mechanism of Action (MOA)

Urinary Tract Infections feverThe two active ingredients in Myospaz work to relieve pain and relax muscles.  Paracetamol is both a pain reliever (analgesic) and a reliever of fever (antipyretic). Paracetamol works by preventing the production of prostaglandins that are associated with inflammation, thus it has weak anti-inflammatory activities. Paracetamol also influences the heat center in the brain, the hypothalamus, as a result, encouraging heat loss from the body. In addition, it blocks the generation of pain impulses from the periphery.

Chlorzoxazone works primarily in the spinal cord and the brain subcortical areas. It works by inhibiting multisynapticreflex arcs that are involved in the production and maintenance of spasm in the skeletal muscles. It inhibits the influx of both calcium ions and potassium ions, this results in neurons not being able to transmit impulses and the muscles relax and the pain is relieved.


Myospaz is not recommended to be used in certain conditions. When used it can worsen the preexisting medical condition or increase the chance of adverse reactions occurring. Inform your doctor of any medical conditions you have or have previously had as they could affect the prescription. The following conditions are contraindicated for Myospaz:

  • Allergic reaction: Do not use Myospaz is you are allergic to the active ingredients.
  • Impaired kidney function.
  • Hepatic impairment: Myospaz is metabolized in the liver thus having a liver disease might interfere with its metabolism.
  • Pregnancy or planning to get pregnant
  • Porphyria
  • Neutropenia
  • Phenylketonuria
  • Asthma
  • Blood coagulation and bleeding disorder
  • Children under the age of 12 years
  • Anemia
  • Gastro-ulceration history
  • Disorders of the gastro-intestine
  • Have had a recent surgery
  • Analgesic nephropathy

Facts on Myospaz

  • The average duration time for the effects of Myospaz lasts for 4-6 hours.
  • The effect of Myospaz should be felt at least an hour after administration. When administers intravenously, the effects take about 30 minutes.
  • Myospaz is well-absorbed from the gastrointestinal tract and peak concentrations occur within an hour or two.
  • Myospaz undergoes metabolism in the liver and excreted from the body through urine.
  • The half-life for elimination of Myospaz metabolites is one hour.
  • Myospaz is not a habit-forming medication.

Side effects

Myospaz can result is a range of side effects. The side effects d not occur in everyone. The side effect depends on the dose, duration of use and individual reaction to the medication. The side effects can be common and less serious while others can be rare and very serious. Report any side effects you have to your doctor for medicals advice. The common side effects of Myospaz include:

  • Dizziness
  • Weakness
  • Sleepiness
  • Stomach upset
  • Lightheadedness
  • Malaise
  • Discolored urine( orange or reddish-purple urine)
  • Upper stomach pain
  • Nausea
  • Restlessness
  • Constipation
  • Nose bleeding
  • Stuffy nose
  • Vomiting
  • Irritability
  • Dry mouth
  • Diarrhea
  • Fever
  • Reduced amount of urine

Rare side effects of Myospaz include:

  • Dyspepsia
  • Mouth ulcers
  • Gastric ulcer
  • Edema
  • Steven- Johnson Syndrome
  • Hepatic toxicity
  • Coffee ground vomit
  • Agranulocytosis
  • Neutropenia
  • Pancytopenia
  • Leukopenia
  • Thrombocytopenia
  • Hypochromic anemia
  • Skin yellowing or eyes
  • Gastrointestinal bleeding
  • Acute renal tubular necrosis
  • Stool that is black
  • Blurred vision
  • Coughing up blood

Myospaz use should be discontinued in case of symptoms of hepatic impairment as it can be fatal. In case of an allergic reaction to Myospaz, report to your doctor immediately or seek medicals attention. The use of Myospaz should be discontinued in this case. Signs of an allergic reaction include:

  • Skin Rashes
  • Itching
  • Difficulty breathing
  • Swelling of lips, face, tongue, and throat.

If you accidentally take an overdose of Myopsaz, report to your doctor or rush into the emergency unit of the nearest health center and carry the medication package with you for identification. Taking an overdose of Myospaz can result in adverse reactions. Early signs of an overdose include vomiting, nausea, headache, lightheadedness, dizziness, and diarrhea while the late signs include severe abdominal pain, urine that is dark colored, yellowing occurring in the eyes and skin.

Drug interactions

Taking two and more drugs at the same time can result in drug interactions. Inform your doctor of all the medications you are taking or have been taking including both prescription drugs, over the counter drugs, dietary supplements and herbal products. Drug interactions prevent your medication from working properly or lead to the occurrence of side effects. The following drugs and products with Myospaz:

  • Phenytoin
  • Leflunomide
  • Sodium nitrate (Concurrent use can result in an increase in the heartbeat, skin being discolored, rashes and headache).
  • Prilocaine, when used together, can cause hypertension, skin discoloration, headache, and dizziness.
  • Medicines for allergy like cetirizine
  • Sedatives
  • Narcotic pain medication like codeine
  • Seizure medications
  • Muscle relaxers
  • Barbiturates
  • Warfarin
  • High cholesterol medications such as cholestyramine
  • HIV and AIDS medications such as Zidovudine
  • Domperidone
  • Metoclopramide
  • Oxyphenbutazone
  • Metamizole
  • Tramadol
  • Alprazolam
  • Aliskiren
  • Juxtapidmipomersen
  • Atorvastatin
  • Diphenhydramine
  • Zolpidem
  • Triazolam
  • Secobarbital
  • Emifentanil
  • Sodium oxybate
  • Primidone
  • Pentazocine
  • Loxapine

What to Do If You Skip a Dose

If you skip a dose of Myospaz, take it as soon as you realize it. If it is time close to your next dose, you can skip the dose, then take the next dose as scheduled and continue with the normal schedule. Do not double the dose to compensate for the missed dose. Frequent dose missing makes your medication to less effective in treating your condition. If you frequently miss does, have a reminder set to remind you or have a family member remind you when it is time for your next dose.


A number of precautions need to be considered before and when you are using Myospaz. The precautions include:

  • Allergic reactions: Do not take Myospaz if you have an allergic reaction o the active ingredients.
  • Liver disease:  Use of Myospaz should be done cautiously as it is metabolized in the liver and thus damage to the liver increases the chance of toxicity. Dose adjustment of Myospaz is recommended in moderate cases but is not to be used if the damage is severe.
  • Renal impairment: Use Myospaz with caution. Dose adjustment is recommended.
  • Pregnant or planning to conceive: Myospaz should be used with caution as no human trials have been conclusive and it can bring harm to the growing fetus. It should only be used when the benefits outweigh the risks.
  • Inform your doctor of all medical conditions you have or have had to prevent adverse reactions due to underlying conditions.
  • Inform your doctor of all medications you are currently using to avoid drug interactions that can be fatal.
  • Taking alcohol together with Myospaz increases the chances of liver damage.
  • If taking Myospaz makes you feel drowsy and dizzy, do not take part in activities that require mental alertness such as driving and operation of heavy machinery.
  • If you are elderly, taking Myospaz might cause increased confusion, dizziness and the falling risk.
  • While taking Myospaz, avoid excessive exposure to sunlight.
  • Avoid using steroids while taking Myospaz.
  • Do not take Myospaz that has expired. Check the package for expiry date when buying. Expired medications might have reduced effectiveness or might lead to toxicity.
  • Myospaz should be stored at room temperature away from sunlight and heat.
  • Always take Myospaz with a meal or after a meal to avoid acid reflux from occurring.
  • Chlorzoxazone one of the key ingredients of Myospaz is known to cause hepatic toxicity that may be fatal. Report any signs of hepatotoxicity to your doctor if you experience any; they include nausea, fatigue, vomiting, anorexia, rash, fever, dark urine and pain in the right upper quadrant.
  • When using Myospaz and pain or fever is not relieved after 10 minutes to one hour after administration, consult your doctor as for an alternative medication.

Different Brands and Manufacturing Companies of the Drug

Myospaz is manufactured by Win-Medicare Pvt Ltd. It is manufactured as a tablet taken orally and can be administered as an injection too. Other products from Win-Medicare Pvt Ltd include:

  • Myospaz Forte tablet contains 500 mg Chlorzoxazone, 50 mg Diclofenac and 325 mg Paracetamol.
  • Myospaz D tablet contains 50 mg Diclofenac and 400 mg Metaxalone
  • Myospaz TH 4 capsule contains 4 mg Thiocolchicoside and 50 mg Diclofenac
  • Myospaz TH 8 capsule contains 8 mg Thiocolchicoside and 50 mg Diclofenac.

Substitutes for the drug

Substitutes of Myopsaz with the same strength and composition include:

  • Duodil tablet – Abbott
  • Myodol tablet – Pegasus Farmaco India Pvt Ltd
  • Myocetamol tablet – Linux Laboratories
  • Saxopas 325 mg/250 mg tablet – Dr.PearlPharmaceuticals
  • Pat Mr tablet – GenfoBioceuticalsPvt Ltd
  • Set Zox tablet – UHC Lifesciences
  • Parafon tablet – Johnson &Johnson Ltd
  • Supergun 500 mg/250 mg tablet – MedoPharma

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