Metaxalone

The mechanism of action of metaxalone in humans has not been established, but may be due to general central nervous system (CNS) depression. Metaxalone has no direct action on the contractile mechanism of striated muscle, the motor end plate, or the nerve fiber.

• Metaxalone is indicated as an adjunct to rest, physical therapy, and other measures for the relief of discomforts associated with acute, painful musculoskeletal conditions. The mode of action of this drug has not been clearly identified, but may be related to its sedative properties.

• Known hypersensitivity to any components of this product. Known tendency to drug induced, hemolytic, or other anemias.contraindicated

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

Serotonin Syndrome Cases of serotonin syndrome, a potentially life-threatening condition, have been reported during concomitant use of serotonergic drugs with Metaxalone used within the recommended dosage range (see PRECAUTIONS: Drug Interactions ) and with Metaxalone as a single agent taken at doses higher than the recommended dose (see OVERDOSAGE ). Serotonergic drugs include selective serotonin reuptake inhibitors (SSRIs), serotonin and norepinephrine reuptake inhibitors (SNRIs), tricyclic antidepressants (TCAs), triptans, 5-HT3 receptor antagonists, opioids (particularly fentanyl, meperidine, and methadone), drugs that affect the serotonergic neurotransmitter system (e.g., mirtazapine, trazodone, tramadol), and drugs that impair metabolism of serotonin (including monoamine oxidase (MAO) inhibitors, both those intended to treat psychiatric disorders and also others, such as linezolid and intravenous methylene blue) (see PRECAUTIONS: Drug Interactions ). Serotonin syndrome symptoms may include mental status changes (e.g., agitation, hallucinations, coma), autonomic instability (e.g., tachycardia, labile blood pressure, hyperthermia), neuromuscular aberrations (e.g., hyperreflexia, incoordination, rigidity), and/or gastrointestinal symptoms (e.g., nausea, vomiting, diarrhea). The onset of symptoms generally occurs within several hours to a few days, but may occur later than that. Discontinue Metaxalone if serotonin syndrome is suspected.

The most frequent reactions to metaxalone include: CNS : drowsiness, dizziness, headache, and nervousness or “irritability”; Digestive : nausea, vomiting, gastrointestinal upset. Other adverse reactions are: Immune System : anaphylaxis, hypersensitivity reaction, rash with or without pruritus; Hematologic : leukopenia; hemolytic anemia; Hepatobiliary : jaundice; CNS : cases of serotonin syndrome, a potentially life-threatening condition, have been reported during concomitant use of serotonergic drugs with metaxalone used within the recommended dosage range and with metaxalone as a single agent taken at doses higher than the recommended dose (see WARNINGS , PRECAUTIONS: Drug Interactions , and OVERDOSAGE ).

Pregnancy Reproduction studies in rats have not revealed evidence of impaired fertility or harm to the fetus due to metaxalone. Post marketing experience has not revealed evidence of fetal injury, but such experience cannot exclude the possibility of infrequent or subtle damage to the human fetus. Safe use of metaxalone has not been established with regard to possible adverse effects upon fetal development. Therefore, metaxalone tablets should not be used in women who are or may become pregnant and particularly during early pregnancy unless, in the judgement of the physician, the potential benefits outweigh the possible hazards.

Metabolism

The pharmacokinetics of metaxalone have been evaluated in healthy adult volunteers after single dose administration of metaxalone under fasted and fed conditions at doses ranging from 400 mg to 800 mg. Absorption Peak plasma concentrations of metaxalone occur approximately 3 hours after a 400 mg oral dose under fasted conditions.

Deaths by deliberate or accidental overdose have occurred with metaxalone, particularly in combination with antidepressants, and have been reported with this class of drug in combination with alcohol. Serotonin syndrome has been reported when metaxalone was used at doses higher than the recommended dose (see WARNINGS and ADVERSE REACTIONS ). When determining the LD 50 in rats and mice, progressive sedation, hypnosis, and finally respiratory failure were noted as the dosage increased. In dogs, no LD 50 could be determined as the higher doses produced an emetic action in 15 to 30 minutes. Treatment - Gastric lavage and supportive therapy. Consultation with a regional poison control center is recommended.

• Jun 21, 2013ANDAANDA203399Amneal Pharms
• Feb 27, 2015ANDAANDA040486Mountain
• Jun 1, 2015NDANDA022503Primus Pharms
• Nov 22, 2016ANDAANDA204770Lannett Co Inc
• Jun 15, 2017ANDAANDA203695Actavis Labs Fl Inc
• Aug 31, 2017ANDAANDA207466Sciegen Pharms

1. 1Completed Suicide2617.9%
2. 2Drug Ineffective2056.2%
3. 3Nausea1965.9%
4. 4Pain1965.9%
5. 5Fatigue1955.9%
6. 6Headache1665.0%
7. 7Toxicity To Various Agents1645.0%
8. 8Fall1594.8%
9. 9Diarrhoea1334.0%
10. 10Dizziness1213.7%
11. 11Death1163.5%
12. 12Dyspnoea1163.5%
13. 13Chronic Kidney Disease1113.4%
14. 14Vomiting1103.3%
15. 15Renal Failure1073.2%

The 7 most recently updated of 7 ClinicalTrials.gov registrations naming Metaxalone as an intervention. Registration is not evidence of efficacy or safety — reference crosswalk only.

• Efficacy of M640 in Acute Lumbosacral Musculoskeletal Conditions.
  Recruiting · Phase 4 · Interventional · 50 enrolled · Primus Pharmaceuticals
  NCT06157177updated 2026-05-12
• Assess the Effect of Metaxalone 640 mg (M640) Compared to Tizanidine 8 mg on Truck Driving Ability and Cognition
  Completed · Phase 4 · Interventional · 20 enrolled · Primus Pharmaceuticals
  NCT06382662updated 2025-08-22
• Study to Assess Drowsiness, Cognition, Fall Risk After Metaxalone 640 mg and Metaxalone 800 mg
  Completed · Phase 4 · Interventional · 20 enrolled · Primus Pharmaceuticals
  NCT06348303updated 2025-08-07
• Pain Control After Lumbar Spine Fusion
  Enrolling by invitation · Phase 4 · Interventional · 428 enrolled · Rothman Institute Orthopaedics
  NCT06484192updated 2024-07-03
• Opioid Free vs. Standard Perioperative Pain Regimen for Anterior Cervical Discectomy and Fusion (ACDF) Surgery
  Terminated · Phase 4 · Interventional · 8 enrolled · Vanderbilt University Medical Center
  NCT04990804updated 2024-01-31
• Ibuprofen Plus Metaxolone, Tizanidine, or Baclofen for Low Back Pain
  Completed · Phase 4 · Interventional · 320 enrolled · Montefiore Medical Center
  NCT03068897updated 2020-08-12
• The Effect of Prolonged Multimodal Analgesic Regimen on Post Hospital Discharge Opioid Use and Pain Control After Primary Total Knee Arthroplasty
  Completed · Interventional · 216 enrolled · Rothman Institute Orthopaedics
  NCT04003350updated 2019-07-01

Frequently asked questions

How does Metaxalone work?

The mechanism of action of metaxalone in humans has not been established, but may be due to general central nervous system (CNS) depression. Metaxalone has no direct action on the contractile mechanism of striated muscle, the motor end plate, or the nerve fiber.

What is Metaxalone used for?

According to FDA labeling, Metaxalone carries indications including: Metaxalone is indicated as an adjunct to rest, physical therapy, and other measures for the relief of discomforts associated with acute, painful musculoskeletal conditions. The mode of action of this drug has not been clearly identified, but may be related to its sedative properties.. This is a reference summary of labeled uses, not medical advice or a treatment recommendation.

What class of drug is Metaxalone?

Metaxalone is classified as Muscle Relaxant, Unknown Cellular or Molecular Interaction, Centrally-mediated Muscle Relaxation, Decreased Central Nervous System Organized Electrical Activity, Striated Muscle Metabolic Alteration.

What are the brand names for Metaxalone?

Metaxalone is marketed under brand names including Skelaxin.

What are the contraindications for Metaxalone?

Metaxalone labeling lists contraindications including: Known hypersensitivity to any components of this product. Known tendency to drug induced, hemolytic, or other anemias.. Always consult the full prescribing information and a clinician.