How Does Skelaxin (Metaxalone) Work? Know Its Side Effects, Overdose

Chemistry- Chemically, the formulation of metaxalone is given as 5-[(3,5- (dimethylphenoxy) methyl]-2-oxazolidinone with an empirical formula of C12H15N03 and molecular weight of 221.25.

How Does Skelaxin (Metaxalone) Work? Know Its Side Effects, Overdose

Physical Characteristics Of Skelaxin- Metaxalone is a crystalline powder. It contains no odor and is white in color and freely soluble in chloroform, methanol, and 96% ethanol. It is not soluble in water or ether. A single tablet is made up of 800 mg of metaxalone, alginic acid, B-Rose Liquid, ammonium calcium alginate, magnesium stearate, and corn starch.

How Does Skelaxin Work– How Metaxalone acts in humans is still to be established. Animal research indicates Metaxalone does not act on actin-myosin complex of skeletal or smooth muscles. Skelaxin causes central anti-anxiety sedative effects resulting in muscle relaxation. Skelaxin does not modulate neurotransmitter at peripheral or central nerve endings.

Recommended Dosage Of Skelaxin- The recommended dose of Metaxalone for adults and children over 12 years of age is one 800 mg tablet three to four times a day.

Absorption- Metaxalone is absorbed by mucosal membrane of small intestine. The peak concentrations occur about three hours after 400 mg dose orally in fasting conditions after which metaxalone concentrations start declining log linearly with terminal half-life of about 9.0 ± 4.8 hour. Bioavailability and first pass metabolism by liver is not well documented.

Skelaxin Distribution- Metaxalone has large volume of distribution (V/F = 800 L) may be secondary to high lipid solubility. Metaxalone binds to protein in plasma but the percentage of protein binding is not well defined.

Metabolism and Elimination- Metaxalone is metabolized by hepatic cytochrome 450 in liver and excreted in urine as unidentified metabolites.

Indication For Use Of Skelaxin (Metaxalone)

Inform Physician Immediately If You Have –

  • Mental status changes like nervousness or irritable behavior
  • If there are any signs of infection like fever or sore throat
  • Jaundiced eyes/skin
  • Unusual fatigue,
  • Fast heartbeat
  • Dark colored urine.

Drug Interaction- Skelaxin is mild to moderate sedative and functions as muscle relaxants by physiological relaxation of Central nervous System. Avoid following drugs/medications.

  • Avoid sedatives, sleeping pills
  • Alcohol
  • Benzodiazepam
  • Opioids
  • Tricyclic antidepressants
  • Muscle relaxants
  • Antiepileptics
  • Anti-histaminic- Anti-allergic and cough medication
  • Avoid natural product and other
  • Vitamins
  • Minerals
  • Herbal products
  • Drugs prescribed

Skelaxin (Metaxalone) Precautions: Avoid taking Skelaxin or discuss with your physician if following disease or illness is suspected or diagnosed. Dosage of Skelaxin should be adjusted or avoided if history suggests renal failure or liver failure.

  • Liver disease
  • Kidney disease
  • Anemia
  • Seizures
  • Dizzy or drowsy
  • Taking with food may increase CNS depression
  • Elderly population may be more vulnerable to this CNS effect
  • Depression

Activities To Avoid If Taking Skelaxin (Metaxalone) –

  • Do not drive
  • Do not use heavy machinery
  • Do not participate in any activity that requires alertness
  • Avoid alcoholic beverages

Drug Abuse And Dependence

Skelaxin is not abused as addicting medications. Dependence on Skelaxin is observed for therapeutic effects and not for addiction.

Skelaxin Withdrawal

Rapid withdrawal will result in withdrawal symptoms.

Avoid Taking Skelaxin Or Metaxalone During Pregnancy- Skelaxin should be avoided during first trimester. Consult obstetrician and neonatologist if medication withdrawal will result in harmful effects. Animal study has not shown any fertility impairment or abnormalities in fetus.

Avoid Taking Skelaxin Or Metaxalone During Breast Feeding- It is still not proven that it is secreted in human milk. As a thumb rule, nursing is not undertaken if a patient is on medications since many medications are eliminated from the body through human milk.

Skelaxin (Metaxalone) Use in Children- Effectiveness in children at or below 12 years of age has still not been proven.

Skelaxin (Metaxalone) Storage:

  • Store at Room Temperature, between 15°C and 30°C (59°F and 86°F).
  • Store away from light and moisture.
  • Keep all medications away from the children and pets.

Side Effects Of Skelaxin (Metaxalone)

Central Nervous System:

  • Drowsiness and dizziness
  • Headache
  • Nervousness or irritable behavior


  • Nausea
  • Vomiting
  • GI upset

Immune System:

  • Hypersensitivity
  • Rashes and/or pruritus


  • Hemolytic anemia

Hepatobiliary (Liver):

  • Jaundice

Aanaphylactoid Reactions:

  • Rare but there have been instances of it with metaxalone.

Symptoms Of Less Serious Side Effects:

  • Drowsiness, Dizziness
  • Feeling nervous or Irritable
  • Headache
  • Mild nausea

Symptoms Of Severe Side Effects:

Signs Of An Allergic Reaction:

  • Hives
  • Difficulty breathing
  • Swelling of your face, lips, tongue, or throat
  • Drowsiness and dizziness
  • Nausea
  • Vomiting

Skelaxin (Metaxalone) Overdose

Skelaxin (Metaxalone) Overdose

Contact US National Poison Hotline at (USA) 1-800-222-1222 and (Health Canada) 1-866-234-2345.

  • Drowsiness
  • Unconscious
  • Persistent vomiting
  • Dark Urine
  • Jaundice
  • Severe headache
  • Slow or shallow breathing
  • Feeling light-headed, or fainting

Missed Dose Of Skelaxin (Metaxalone)

  • Take the next dose as prescribed
  • Do not take additional pills or double your dose

Carcinogenesis, Mutagenesis, Impairment of Fertility

The carcinogenic potential of metaxalone has not been determined.

Pramod Kerkar, M.D., FFARCSI, DA
Pramod Kerkar, M.D., FFARCSI, DA
Written, Edited or Reviewed By: Pramod Kerkar, M.D., FFARCSI, DA Pain Assist Inc. This article does not provide medical advice. See disclaimer
Last Modified On:October 29, 2019

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