Metaxalone

St. Marys Medical Park Pharmacy

Metaxalone

FULL PRESCRIBING INFORMATION

DESCRIPTION

Metaxalone tablets are available as an 800 mg oval, convex pink tablet.

Chemically, metaxalone is 5-[(3,5- dimethylphenoxy) methyl]-2-oxazolidinone. The empirical formula is C12H15NO3, which corresponds to a molecular weight of 221.25. The structural formula is:

Metaxalone is a white to almost white, odorless crystalline powder freely soluble in chloroform, soluble in methanol and in 96% ethanol, but practically insoluble in ether or water.

Each tablet contains 800 mg metaxalone and the following inactive ingredients: alginic acid, ammonium calcium alginate, B-Rose Liquid, corn starch and magnesium stearate.

CLINICAL PHARMACOLOGY

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

Pharmacokinetics

The pharmacokinetics of metaxalone have been evaluated in healthy adult volunteers after single dose administration of Metaxalone tablets 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. Thereafter, metaxalone concentrations decline log-linearly with a terminal half-life of 9.0 ± 4.8 hours. Doubling the dose of metaxalone tablets from 400 mg to 800 mg results in a roughly proportional increase in metaxalone exposure as indicated by peak plasma concentrations (Cmax) and area under the curve (AUC). Dose proportionality at doses above 800 mg has not been studied. The absolute bioavailability of metaxalone is not known.

The single-dose pharmacokinetic parameters of metaxalone in two groups of healthy volunteers are shown in Table 1

Uses

INDICATIONS AND USAGE
Metaxalone tablets 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. Metaxalone does not directly relax tense skeletal muscles in man.

CONTRAINDICATIONS

Known hypersensitivity to any components of this product.

Known tendency to drug induced, hemolytic, or other anemias.

Significantly impaired renal or hepatic function.

WARNINGS

Metaxalone tablets may enhance the effects of alcohol and other CNS depressants.

PRECAUTIONS
Metaxalone should be administered with great care to patients with pre-existing liver damage.  Serial liver function studies should be performed in these patients.

False-positive Benedict's tests, due to an unknown reducing substance, have been noted.  A glucose-specific test will differentiate findings.

Taking metaxalone tablets with food may enhance general CNS depression; elderly patients may be especially susceptible to this CNS effect.  (See CLINICAL PHARMACOLOGY: Pharmacokinetics and PRECAUTIONS: Information for Patients sections)

Information for Patients

Metaxalone tablets may impair mental and/or physical abilities required for performance of hazardous tasks, such as operating machinery or driving a motor vehicle, especially when used with alcohol or other CNS depressants.

Drug Interactions

The sedative effects of metaxalone tablets an dother CNS depressants (e.g., alcohol benzodiazepines, opiods, trycyclic antidepressants)  may be additive.  Therefore, caution should be exercised with patients who take more than one of these CNS depressants simultaneoulsy.

Carcinogenesis, Mutagenesis, Impairment of Fertility

The carcinogenic potential of metaxalone has not been determined.

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.

NURSING MOTHERS

It is not known whether this drug is secreted in human milk. As a general rule, nursing should not be undertaken while a patient is on a drug since many drugs are excreted in human milk.

Pediatric Use

Safety and effectiveness in children 12 years of age and below have not been established.

ADVERSE REACTIONS

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: hypersensitivity reaction, rash with or without pruritus;

Hematologic: leukopenia; hemolytic anemia;

Hepatobiliary: jaundice.

Though rare, anaphylactoid reactions have been reported with metaxalone.

OVERDOSAGE

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.

When determining the LD50 in rats and mice, progressive sedation, hypnosis and finally respiratory failure were noted as the dosage increased. In dogs, no LD50 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.

DOSAGE AND ADMINISTRATION

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

HOW SUPPLIED

Metaxalone tablets are available as an 800 mg oval, convex, pink tablet with one side debossed "M" and other side debossed "58/59".

                    Bottles of 100            NDC 64720-321-10
                    Bottles of 500            NDC 64720-321-50

Store at Controlled Room Temperature, between 15°C and 30°C (59°F and 86°F).

Rx Only

Manufactured and Distributed by:

Corepharma LLC
Middlesex, NJ  08846

MF#  704-01                                                      April 2010

NDC 60760-054-30

METAXALONE TABLETS

800 MG

QTY: 30
LOT#  XXXXXXX
EXP   XX-XX
RX#   0000000

MANUFACTURED BY:
Corepharma LLC
Middlesex, NJ 08846

PACKAGED BY:

St. Mary's MPP
10660 MAVINEE DR.
ORO VALLEY, AZ 85737

MANAGED PHARMACY PROGRAMS

METAXALONE
TABLETS

800 MG
QTY: 30
RX#   0000000
NDC 60760-054-30
LOT#  XXXXXXX
EXP   XX-XX

TAKE .. TAB .. TIMES A DAY OR EVERY .. HOURS MAY CAUSE DROWSINESS

Rx only  STORE AT CONTROLLED ROOM TEMPERATURE 15-30 degree CENTIGRADE (59-86 degree FAHRENHEIT)