Uses
Muscular Conditions
Adjunct to rest, physical therapy, analgesics, and other measures for the relief of discomfort associated with acute, painful musculoskeletal conditions.
For low back pain, generally reserve skeletal muscle relaxants for adjunctive treatment when pain is unresponsive to OTC analgesics (e.g., NSAIAs).
Skeletal muscle relaxants less well tolerated than NSAIAs, and clinical superiority to NSAIAs not established for low back pain.
Various skeletal muscle relaxants appear to have comparable efficacy for low back pain relief and are more effective than placebo.
Initially, symptomatic control of acute low back pain focuses on providing sufficient comfort to allow maximum possible activity while awaiting spontaneous recovery; later, as aid to overcome specific activity intolerance.
Because of rapid spontaneous recovery rate, efficacy of various therapies may be difficult to establish; improvement of low back pain usually occurs within 2 weeks, substantial improvement within 4 weeks.
Ineffective in the treatment of skeletal muscle hyperactivity secondary to chronic neurologic disorders (e.g., cerebral palsy) and other dyskinesias.
Dosage and Administration
Administration
Oral Administration
Administer orally.
Manufacturer makes no specific recommendations regarding administration with meals; administration with high-fat meal increases absorption, but clinical importance is unknown. (See Food under Pharmacokinetics.)
Dosage
Pediatric Patients
Muscular Conditions
Oral
Children >12 years of age: 800 mg 3 or 4 times daily.
Adults
Muscular Conditions
Oral
800 mg 3 or 4 times daily.
Cautions
Contraindications
- History of drug-induced, hemolytic, or other anemia.
- Substantial hepatic or renal impairment.
- Known hypersensitivity to metaxalone or any ingredient in the formulation.
Warnings/Precautions
Warnings
CNS Depressants
May enhance the effects of other CNS depressants. (See Specific Drugs and Laboratory Tests under Interactions.)
Sensitivity Reactions
Hypersensitivity Reactions
Possible hypersensitivity reactions.
Specific Populations
Pregnancy
Category B.
Animal studies have failed to reveal fetal risk, but safe use during pregnancy has not been established; do not use in women who are or may become pregnant unless possible benefits outweigh potential risks.
Lactation
Not known whether metaxalone is distributed into milk. Use not recommended.
Pediatric Use
Safety and efficacy not established in children ≤12 years of age.
Geriatric Use
Use with caution due to greater frequency of decreased hepatic or renal function and of concomitant disease and drug therapy observed in the elderly.
Hepatic Impairment
Use great caution in patients with a history of liver disease. Perform liver function tests periodically during metaxalone therapy.
Contraindicated in patients with substantial hepatic impairment.
Renal Impairment
Caution advised; contraindicated in patients with substantial renal impairment.
Common Adverse Effects
Drowsiness, dizziness, headache, nervousness or irritability, nausea, vomiting, GI upset.
Drug Interactions
Specific Drugs and Laboratory Tests
| Drug or Test |
Interaction |
Comments |
| CNS depressants (e.g., alcohol, barbiturates) |
Additive CNS depression |
Use caution to avoid overdosage |
| Tests for glucose that utilize cupric sulfate (Benedict’s Solution, Clinitest®, Fehling’s Solution) |
Possible false-positive results |
|
| Tests for glucose that utilize glucose oxidase (Clinistix®, Diastix®, Tes-Tape® |
No interference with test |
|
Pharmacokinetics
Absorption
Bioavailability
Absolute bioavailability not determined.
Onset
Usually within 1 hour.
Duration
About 4–6 hours.
Food
High-fat meal delays time to peak plasma concentration by about 1–2 hours, increases peak plasma concentration by 178–194%, and increases extent of absorption (AUC) by 115–142%; clinical importance unknown.
Distribution
Extent
Not known whether metaxalone crosses the placenta or is distributed into milk.
Elimination
Metabolism
Metabolized in the liver.
Elimination Route
Excreted in urine as unidentified metabolites.
Half-life
About 2–4 hours.
Stability
Storage
Oral
Tablets
15–30°C.
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