Metaxalone
SKELAXIN
Pronunciation: me-TAX-a-loen
“Skeletor Relaxin’ (with a) Meat ax, alone”
Mao Zedong → monoamine oxidase (MAO) inhibitor
What it isCentral muscle relaxant of uncertain mechanism; acute musculoskeletal spasm.
Why this oneIt impairs alertness less than many skeletal muscle relaxants, but direct evidence of benefit is unusually thin.
What limits itFood raises exposure, and alcohol or opioids amplify sedation; rare hemolytic anemia and hepatotoxicity occur.
FDA-approved for
- muscle spasm (1962)
FDA label
Read the full label on DailyMed ↗
| FDA dosing | Population | Start | Target | Max |
|---|---|---|---|---|
| Acute painful musculoskeletal conditions (adjunct) | Adults & children >12 yr | 800 mg TID–QID | 800 mg TID–QID | 3200 mg/day |
Renal Contraindicated in significantly impaired renal function
Hepatic Contraindicated in significantly impaired hepatic function
Available strengths
- tab 400, 640, 800 mg
Contraindications
- Known tendency to drug-induced, hemolytic, or other anemias
- Significantly impaired renal or hepatic function
Cautions
- Serotonin syndrome reported with concomitant serotonergic drugs (and at higher-than-recommended doses as single agent)
- Drowsiness/dizziness — may impair driving
- Hemolytic anemia; leukopenia
- Hypersensitivity/anaphylaxis; rash
- Jaundice
Adverse reactions
- Drowsiness
- Dizziness
- Headache
- Nervousness/irritability
- Nausea
- Vomiting
- GI upset
Pregnancy Safe use not established; should not be used in women who are or may become pregnant, particularly in early pregnancy, unless benefit outweighs hazard
Lactation Undefined
Cost
Generic entry2010
NO BOXED WARNINGS
Principal riskWeak efficacy evidence; take with food
Classes and tags
Clinical profile
Legacy pregnancy categoryUnknown / historical label unavailable
Defining liabilityGenerally tolerated at therapeutic doses; clinically important risks are agent-specific and increase with interactions or organ impairment.
Serotonin and MAOI
Provisional washout figures
Elevating mechanismMAO-A inhibitor
Non-elevating actionNone recorded
Exposure dependencePrimarily supratherapeutic/overdose exposure
Washout AFTER an MAOIU days
Evidence confidenceModerate
InterpretationWeak MAO-A inhibition, most relevant at supratherapeutic or overdose exposure.
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