METAXALONE

Metaxalone tablets, USP contain 800 mg of metaxalone, USP and the following inactive ingredients: alginic acid, ammonium alginate, calcium alginate, corn starch, magnesium stearate and pregelatinized starch (starch 1500 partially pregelatinized maize starch). Metaxalone tablets, USP is a muscle relaxant for oral administration. Chemically, metaxalone is 5-[(3,5-dimethylphenoxy) methyl]-2-oxazolidinone. The molecular formula is C 12 H 15 NO 3 , which corresponds to a molecular weight of 221.25. The structural formula is: Metaxalone, USP 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. Meets USP dissolution test 2. 1

Metaxalone tablets are indicated as an adjunct to rest, physical therapy, and other measures for the relief of discomfort associated with acute, painful musculoskeletal conditions in adults and pediatric patients 13 years of age and older. Metaxalone tablets are a muscle relaxant indicated as an adjunct to rest, physical therapy, and other measures for the relief of discomforts associated with acute, painful musculoskeletal conditions in adults and pediatric patients 13 years of age and older. ( 1 )

The recommended dosage of metaxalone tablets in adults and pediatric patients 13 years of age and older is 800 mg orally three to four times a day [see Use in Specific Populations ( 8 )]. Metaxalone tablets 800 mg are not substitutable on a mg to mg basis with metaxalone tablets, 640 mg [see Clinical Pharmacology ( 12.3 )]. When it is appropriate to switch: Switch only in patients who have been taking metaxalone tablets, 640 mg on an empty stomach. Stop metaxalone tablets, 640 mg three times a day and start metaxalone tablets 800 mg three times a day on an empty stomach, OR stop metaxalone tablets 640 mg four times a day and start metaxalone tablets 800 mg four times a day on an empty stomach. Do not switch from metaxalone tablets, 640 mg to metaxalone tablets when the patient is taking food during administration. Recommended dosage of metaxalone tablets in adults and pediatric patients 13 years of age and older is 800 mg orally three to four times a day. ( 2 ) Metaxalone tablets 800 mg are not substitutable on a mg to mg basis with metaxalone tablets, 640 mg. When it is appropriate to switch, see the Full Prescribing Information on switching instructions. ( 2 )

Metaxalone tablets are contraindicated in patients with: Known hypersensitivity to any component of metaxalone tablets. Known tendency to drug induced, hemolytic, or other anemias. Severe renal or hepatic impairment. Known hypersensitivity to any components of this product. ( 4 ) Known tendency to drug induced, hemolytic, or other anemias. ( 4 ) Severe renal or hepatic impairment. ( 4 )

The following adverse reactions associated with the use of metaxalone tablets were identified in clinical studies or postmarketing reports. Because some of these reactions were reported voluntarily from a population of uncertain size, it is not always possible to reliably estimate their frequency or establish a causal relationship to drug exposure. The most frequent reactions to metaxalone were: CNS : drowsiness, dizziness, headache, and nervousness or "irritability". Digestive : nausea, vomiting, gastrointestinal upset. Other adverse reactions were: CNS : cases of serotonin syndrome have been reported during concomitant use of metaxalone tablets (within the recommended dosage range) and other serotonergic drugs and with the use of metaxalone tablets as the only serotonergic drug at a dosage higher than the recommended dosage [see Warnings and Precautions ( 5.1 ), Drug Interactions ( 7.1 ) and Overdosage ( 10 )]. Hematologic : leukopenia; hemolytic anemia; Hepatobiliary : jaundice; Immune System : anaphylaxis, hypersensitivity reaction, rash with or without pruritus. Most common adverse reactions (incidence >5%) are nausea and vomiting. ( 6 ) To report SUSPECTED ADVERSE REACTIONS, contact Actavis at 1-888-838-2872 or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch.

7.1 Serotonergic Drugs If concomitant use of metaxalone tablets and another serotonergic drug is warranted, carefully observe the patient, particularly during treatment initiation and dosage modification. Discontinue metaxalone tablets if serotonin syndrome is suspected or if it occurs. Serotonin syndrome has resulted from concomitant use of metaxalone tablets (within the recommended dosage range) with other serotonergic drugs [see Warnings and Precautions ( 5.1 ) and Adverse Reactions ( 6 )]. Serotonergic drugs include selective serotonin reuptake inhibitors (SSRIs), serotonin and norepinephrine reuptake inhibitors (SNRIs), tricyclic antidepressants (TCAs), triptans, 5-HT3 receptor antagonists, opioids (particularly fentanyl, meperidine, and methadone), drugs that affect the serotonergic neurotransmitter system (e.g., mirtazapine, trazodone, tramadol), and drugs that impair metabolism of serotonin (including monoamine oxidase (MAO) inhibitors, both those intended to treat psychiatric disorders and also others, such as linezolid and intravenous methylene blue). 7.2 CNS Depressants If concomitant use of metaxalone tablets and another CNS depressant is warranted, closely monitor for signs of respiratory depression and sedation, particularly during treatment initiation and dosage increases. Due to the additive pharmacologic effect, concomitant use of metaxalone tablets with other CNS depressants may increase the risk of sedation and respiratory depression [see Warnings and Precautions ( 5.2 )]. 7.3 Interaction of Metaxalone Tablets with Benedict’s Tests False-positive Benedict's tests, due to an unknown reducing substance, have been noted in metaxalone tablets-treated patients. A glucose-specific test will differentiate findings.