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Medication Safety Issues
Sound-alike/look-alike issues:
Metaxalone may be confused with metolazone
Pronunciation
(me TAKS a lone)
U.S. Brand Names
Generic Available
No
Canadian Brand Names
Pharmacologic Category
Pharmacologic Category Synonyms
Use
Relief of discomfort associated with acute, painful musculoskeletal conditions
Pregnancy Risk Factor
C
Lactation
Excretion in breast milk unknown/not recommended
Contraindications
Hypersensitivity to metaxalone or any component of the formulation; impaired hepatic or renal function, history of drug-induced hemolytic anemias or other anemias
Warnings/Precautions
Concerns related to adverse effects:
• CNS depression: May cause CNS depression, which may impair physical or mental abilities; patients must be cautioned about performing tasks which require mental alertness (eg, operating machinery or driving).
Disease-related concerns:
• Hepatic impairment: Use with caution in patients with hepatic impairment; routine monitoring of transaminases is recommended.
• Renal impairment: Use with caution in patients with renal impairment.
Concurrent drug therapy issues:
• Sedatives: Effects may be potentiated when used with other sedative drugs or ethanol.
Special populations:
• Elderly: Use with caution in the elderly; may be more sensitive to CNS effects.
• Females: An increase in bioavailability and half-life have been observed in female patients.
Adverse Reactions
Frequency not defined.
Central nervous system: Dizziness, drowsiness, headache, irritability, paradoxical stimulation
Dermatologic: Rash (with or without pruritus)
Gastrointestinal: Gastrointestinal upset, nausea, vomiting
Hematologic: Hemolytic anemia, leukopenia
Hepatic: Jaundice
Miscellaneous: Hypersensitivity (including anaphylactoid reactions)
Drug Interactions
CNS depressants: Metaxalone may increase effects/toxicity of other CNS depressants such as anticonvulsants, antihistamines, antipsychotics, barbiturates, benzodiazepines, opiates, phenothiazines, selective serotonin reuptake inhibitors, and tricyclic antidepressants.
Ethanol/Nutrition/Herb Interactions
Ethanol: Avoid ethanol (may increase CNS depression).
Food: Bioavailability may be increased (may increase CNS depression).
Herb/Nutraceutical: Avoid valerian, St John's wort, kava kava, gotu kola (may increase CNS depression).
Storage
Store at room temperature at 15°C to 30°C (59°F to 86°F).
Mechanism of Action
Precise mechanism has not been established; however, efficacy appears to result from disruption of the spasm-pain-spasm cycle, probably by a general CNS depressant effect. Does not have a direct effect on skeletal muscle.
Pharmacodynamics/Kinetics
Onset of action: ?1 hour
Duration: ?4-6 hours
Metabolism: Hepatic
Bioavailability: Not established; food may increase
Half-life elimination: 9 hours
Time to peak: Tmax: 3 hours
Excretion: Urine (as metabolites)
Dosage
Children >12 years and Adults: Oral: 800 mg 3-4 times/day
Administration: Oral
May be administered with or without food. However, serum concentrations may be increased when administered with food; clinical significance has not been established. Patients should be monitored.
Test Interactions
False-positive Benedict's test
Dietary Considerations
Administration with food may increase serum concentrations.
Dental Health: Effects on Dental Treatment
No significant effects or complications reported
Dental Health: Vasoconstrictor/Local Anesthetic Precautions
No information available to require special precautions
Mental Health: Effects on Mental Status
Drowsiness and dizziness are common; may cause paradoxical stimulation
Mental Health: Effects on Psychiatric Treatment
May cause leukopenia; use caution with clozapine and carbamazepine; concurrent use with psychotropics may produce additive sedation
Dosage Forms
Excipient information presented when available (limited, particularly for generics); consult specific product labeling. [DSC] = Discontinued product
Tablet: 400 mg [DSC], 800 mg
Pricing: U.S. (www.drugstore.com)
Tablets (Skelaxin)
800 mg (30): $101.16
References
Toth PP and Urtis J, “Commonly Used Muscle Relaxant Therapies for Acute Low Back Pain: A Review of Carisoprodol, Cyclobenzaprine Hydrochloride, and Metaxalone,” Clin Ther, 2004, 26(9):1355-67.
International Brand Names
Lexi-Comp.com
Last full review/revision January 2008
Content last modified January 2008
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