Metaxalone

Pronunciation

Pronunciation: me-TAX-a-lone
Class: Skeletal muscle relaxant

Trade Names

Skelaxin
- Tablets 800 mg

Pharmacology

Mechanism of action not established, but may be caused by general CNS depression. No direct action on the contractile mechanism of striated muscle, the motor endplate, or the nerve fiber. Does not directly relax tense skeletal muscles.

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Pharmacokinetics

Under fasting conditions, C max is 1653 ng/mL, T max is approximately 3 h and mean t ½ is 8 h. Under fed conditions, C max increased by 194%, T max is approximately 4.9 h and mean t ½ is 4.2 h (single 800 mg dose).

Indications and Usage

As an adjunct to rest, physical therapy, and other measures for the relief of discomfort associated with acute, painful, musculoskeletal conditions.

Contraindications

Standard considerations; known tendency to drug-induced hemolytic or other anemias; significantly impaired renal or hepatic function.

Dosage and Administration

Adults and children older than 12 yr of age

PO 800 mg 3 to 4 times daily.

Storage/Stability

Store tablets at controlled room temperature (59° to 86°F).

Drug Interactions

Alcohol, barbiturates, CNS depressants

Effects may be enhanced by metaxalone.

Laboratory Test Interactions

False-positive Benedict tests, caused by an unknown reducing substance, have been noted. A glucose-specific test will differentiate findings.

Adverse Reactions

CNS

Drowsiness; dizziness; headache; nervousness; irritability.

GI

Nausea; vomiting; GI upset.

Miscellaneous

Hypersensitivity reaction (light rash with or without pruritus); leukopenia; hemolytic anemia; jaundice; anaphylactoid reactions (rare).

Precautions

Pregnancy

Do not use during pregnancy, especially during early pregnancy, or in women who may become pregnant, unless the potential benefits outweigh the potential hazards to the fetus.

Lactation

Undetermined.

Children

Safety and efficacy not determined in children younger than 12 yr of age.

Hepatic Function

Administer with great care to patients with preexisting liver damage and perform serial liver function studies as required.

Patient Information

  • Advise patient or caregiver to read the patient information leaflet before starting therapy and with each refill.
  • Advise patient that medication is usually started at a low dose and then gradually increased until max benefit is obtained.
  • Caution patient to take as prescribed and not to stop taking or change the dose unless advised by health care provider.
  • Advise patient to take each dose without regard to meals but to take with food if stomach upset occurs.
  • Advise patient that if a dose is missed to skip that dose and take the next dose at the regularly scheduled time. Caution patient to never take 2 doses at the same time.
  • Instruct patient to avoid alcoholic beverages and other depressants while taking this medication.
  • Emphasize importance of other adjunctive measures (eg, rest, physical therapy) as part of the management of musculoskeletal conditions.
  • Instruct patient to contact health care provider if symptoms do not appear to be getting better, are getting worse, or if skin rash, yellowish discoloration of the skin or eyes, or bothersome adverse reactions (eg, drowsiness, dizziness, nausea) occur.
  • Advise patient that drug may cause drowsiness or dizziness and to use caution while driving or performing other tasks requiring mental alertness until tolerance is determined.

Copyright © 2009 Wolters Kluwer Health.

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