Metaxalone for Muscle Spasms: A Comprehensive Overview

Overview

Metaxalone is used for the treatment of skeletal muscle pain. The drug treats muscle spasms and relieves discomfort and pain in muscle strains, sprains, and injuries. It is usually prescribed as an adjunct to physical exercise, rest, and other measures to treat the condition; however, the drug is not a substitute for any other treatment recommended by the doctor for muscle spasms. Also, the exact mechanism of the drug’s action is not known, and it may be due to the general central nervous system depression caused by the drug. The FDA (Food and Drug Administration) approved the drug in June 2002. Therefore, the article discusses the drug’s indications, side effects, contraindications, clinical pharmacology, warnings and precautions, and drug dosage.

Drug Group

Metaxalone is a skeletal muscle relaxant and neuromuscular blocking agent. It primarily belongs to a class of drugs called oxazolidinone.

Indications

The drug is indicated for treating muscle spasms in addition to physical therapy, rest, and other measures to relieve discomfort and pain.

Dose Form, Route, and Strength

The drug is available in tablet form in three strengths: 400 mg (milligrams), 640 mg, and 800 mg, to be taken orally or through the mouth.

For Patients:

What Is Muscle Spasm?

Muscle spasms or cramps are temporary and harmless involuntary contractions of the muscles that may also cause pain. They are a common condition that can occur in any part of the body and may involve a single or group of muscles. Muscle spasms may or may not be linked to any underlying medical condition.

What Is Metaxalone Prescribed For?

Metaxalone is prescribed for treating muscle spasms caused by strains, sprains, and injuries. It relieves the discomfort and pain caused by muscle spasms and is mainly used with other measures, such as physical therapy and rest, to relax the muscles.

How Should Metaxalone Be Taken?

The drug is available in tablet form to be taken orally (through mouth) three or four times daily. A person should follow the prescription labels cautiously and must ask the pharmacist or the doctor if they do not understand any part of the instructions given on the label. Also, the drug should be taken strictly according to the doctor's prescription. Without consulting the doctor, one should not alter the drug dosage, duration, and frequency.

What Are the Precautions to Follow Before Taking Metaxalone?

• Before starting treatment with Metaxalone, the doctor must be informed about allergic reactions to the drug, its ingredients, or any other drug.

• The doctor should also be informed about past or present medical history, such as liver disease, kidney disease, blood disorders, and seizures (uncontrolled electrical activity in the brain cells).

• A person should also inform the doctor about all the non-prescription and prescription drugs they are taking or planning to take, such as herbal products, vitamins, and nutritional supplements. The doctor might need to adjust or change the drug dosages or monitor the patient carefully while treating with Metaxalone.

• Metaxalone is known to cause drowsiness; therefore, it is best to avoid driving a car or operating heavy machinery while taking the medication.

• One must also avoid alcohol while taking Metaxalone as it can also add to the effects of drowsiness caused by the drug.

• If a person is 65 years or older, they must ask the doctor about all the benefits and risks of taking Metaxalone. Older people should avoid the drug as it is not effective and safe for this age group, and some other medication can be used to treat the condition in these people.

• One must also tell the doctor if they are pregnant or planning to conceive or get pregnant while taking the drug. The doctor must be informed immediately.

What Are the Side Effects of Metaxalone?

One must consult the doctor immediately if these symptoms worsen or become severe.

Common Side Effects:

• Headache.

• Drowsiness.

• Nervousness.

• Dizziness.

Serious Side Effects:

• Vomiting, nausea, and diarrhea.

• High body temperature and rapid heart rate.

• Bleeding and bruising.

• Breathing difficulties.

• Loss of muscle control and muscle twitching.

• Weakness and tiredness.

• Skin rash.

• Seizures.

• Hallucinations (having false perception about everything involving senses), agitation (nervousness or anxiety), and coma.

• Yellowish discoloration of skin and eyes.

Drug Dosage and Administration

• The recommended drug dosage for adults and pediatric patients (above 12 years of age and older) is 640 milligrams taken orally (through mouth) three or four times daily, with or without food.

• The maximum recommended daily drug dosage is not more than four tablets or 2,560 milligrams.

• Due to varying pharmacokinetic profiles, 640 mg (milligrams) and 800 mg of Metaxalone tablets are not recommended to be mutually substitutable on a mg-to-mg basis.

• It is appropriate to switch the drug dosages or strengths in individuals who have been taking either strength on an empty stomach.

• It is recommended to discontinue Metaxalone 800 mg (milligrams) three times a day and prescribe Metaxalone tablets 640 milligrams three times a day to an individual on an empty stomach, or discontinue Metaxalone 800 mg four times daily and prescribe Metaxalone tablets 640 mg four times a day to an individual on an empty stomach.

• Switching dosages (from 640 mg to 800 mg) for individuals who have been taking both doses with food is not recommended.

Missed Dose

If one misses the drug dosage of Metaxalone, they must consume it as soon as they remember it. However, if it is already time for the next scheduled dose, one must continue taking it and skip the missed one. Do not take the double drug dosage to compensate for the missed one.

Overdose

The poison control helpline should be contacted in case of an overdose of the drug. However, emergency medical services must be contacted immediately if a person has breathing issues, seizures, or collapses.

Drug Storage and Disposal

The drug should be kept in an airtight container away from children’s reach. It should be stored at a controlled room temperature of 20 to 25 degrees Celsius or 68 to 77 degrees Fahrenheit, with excursions permitted to 15 to 30 degrees Celsius or 59 to 86 degrees Fahrenheit.

Expired and unneeded medication should be discarded safely to ensure that they are not consumed by anyone accidentally or intentionally. The drug should not be flushed into the toilets. One can contact the nearest pharmacist or garbage or recycling department to discard the drug through a take-back program. However, suppose a person does not have access to the take-back program. In that case, by visiting the website, they can dispose of the drug following the FDA’s (Food and Drug Administration) guidelines and protocols for safe disposal.

For Doctors:

Clinical Pharmacology:

Mechanism of Action

The drug’s mechanism of action in treating muscle spasms is not yet established in humans. However, it may be due to the general central nervous system depression caused by the drug. The drug does not directly affect the contractile mechanism of striated muscle, the motor end plate, or the nerve fiber.

Pharmacodynamics

The time course and the exposure-response relationship of Metaxalone’s pharmacodynamics for safety and effectiveness have not been fully established.

Pharmacokinetics

• Absorption: The peak plasma concentration of the drug occurs within three hours after taking 400 milligrams of oral dosage without a meal. Increasing the dose from 400 to 800 milligrams is expected to result in a proportional increase in drug exposure. Also, the absolute bioavailability of the drug has yet to be established.

• Distribution: The drug's volume of distribution is 800 liters (L). However, the drug's plasma protein binding is not known.

• Metabolism: The drug gets metabolized by the hepatic system or liver.

• Excretion: The drug gets excreted in urine through unidentified metabolites.

Ingredients

• Active Ingredient: Metaxalone.

• Inactive Ingredients: Lactose monohydrate, povidone, alginic acid, propylene glycol alginate, magnesium stearate, and FD and C Yellow No. 6.

Contraindications

The drug is contraindicated in the following cases:

• Any known history of hypersensitivity reaction to Metaxalone or any of its components.

• Significant hepatic (liver) or renal (kidney) impairment.

• History of drug-induced hemolytic anemia (unusual breakdown of red blood cells due to some medicine).

What Are the Warnings and Precautions For Metaxalone?

CNS or Central Nervous System Depression:

Metaxalone is known to cause central nervous system depressant effects, thus leading to impaired physical and mental abilities needed for performing hazardous tasks, such as driving a vehicle or operating machinery, especially when the drug is used with other central nervous system depressants and alcohol. Elderly patients are also more susceptible to CNS depression linked with Metaxalone use. Additionally, the concomitant use of Metaxalone and other central nervous system depressants, such as benzodiazepines, alcohol, tricyclic antidepressants, and opioids, cause sedative effects that may be additive. A class of skeletal muscle relaxants has also been known to cause drowsiness or sedation to varying degrees.

A crossover trial with Metaxalone 800 milligrams (mg) tablets reported 10.7 percent of adverse effects related to nervous system disorders, such as dizziness, headache, and lethargy, and zero percent side effects among individuals taking 640 mg of the drug. However, individuals who have been prescribed Metaxalone Tablets, 640 mg, must be closely monitored for symptoms of sedation and respiratory depression (ineffective and slow breathing). In case of concomitant use of the drug and another central nervous system depressant, the patient must be monitored carefully for signs of sedation and respiratory depression, especially during the start of the treatment and dosage modification.

Thus, the patient should be monitored carefully during dose initiation and modification while prescribing Metaxalone.

Serotonin Syndrome:

The drug is also known to cause a life-threatening condition called serotonin syndrome (a condition caused by the use of serotonin drugs), which can occur within the recommended dosage range and also with other serotonergic drugs. The syndrome can also occur with the use of the drug as the only serotonergic drug prescribed at a dosage higher than the recommended dosage. Examples of serotonergic drugs include serotonin and norepinephrine reuptake inhibitors (SNRIs), selective serotonin reuptake inhibitors (SSRIs), tricyclic antidepressants (TCAs), opioids (such as Fentanyl, Methadone, and Meperidine) affecting the serotonergic neurotransmitter system (such as Mirtazapine, Tramadol, and Trazodone), triptans, 5-HT3 receptor antagonists drugs, and also the drugs that impair metabolism of serotonin, such as Monoamine oxidase (MAO) inhibitors, which intend to treat psychiatric disorders and also other drugs, such as Linezolid and intravenous Methylene blue.

The symptoms of serotonin syndrome may occur a few days after a few days of starting a treatment or even much later than that. The symptoms include changes in mental status (including hallucinations, agitation, and coma), neuromuscular aberrations (including hyperreflexia (overactive reflex response by the skeletal muscles), rigidity, and incoordination), autonomic instability (including hyperthermia (overheating or abnormally high temperature), tachycardia (rapid irregular or regular heart rate), and labile blood pressure, and or gastrointestinal symptoms (including vomiting, nausea, and diarrhea). Therefore, the patient must be carefully monitored if prescribed Metaxalone or any other serotonergic drugs, especially during the start of the treatment and dose modification.

Associated Risks with Inappropriate Switching of Metaxalone Tablets:

Inappropriate switching on a mg-to-mg basis from Metaxalone Tablets, 640 (milligrams) to 800 mg to achieve total daily drug dosage may significantly decrease Metaxalone exposure and effect clinically. The drug tablets 640 and 800 milligrams cannot be mutually substitutable on a mg-to-mg basis.

Switching between 640 and 800-milligram tablets is generally not recommended to treat Metaxalone-associated hypersensitive or allergic adverse reactions.

Drug Interactions

• Alcohol.

• Amphetamine or Dextroamphetamine.

• Naproxen.

• Fexofenadine.

• Zolpidem.

• Aspirin.

• Diphenhydramine.

• Celecoxib.

• Ubiquinone.

• Rosuvastatin.

• Duloxetine.

• Fish Oil (omega-3 polyunsaturated fatty acids).

• Cyclobenzaprine.

• Fluticasone nasal.

• Escitalopram.

• Pregabalin.

• Metoprolol.

• Acetaminophen or Hydrocodone.

• Albuterol.

• Montelukast.

• Levothyroxine.

• Acetaminophen.

• Vitamin B12.

• Vitamin C.

• Vitamin D2.

• Vitamin D3.

• Bupropion.

• Alprazolam.

• Ondansetron.

• Sertraline.

• Cetirizine.

Use in Specific Populations:

Pregnancy

No specific data is available on the use of the drug in pregnancy to evaluate the risks associated with the drug, such as miscarriage, major birth defects, or other adverse fetal or maternal outcomes with the use of Metaxalone. The drug does not have any known evidence of impaired fertility or harm to the fetus in reproduction studies on rats as well. However, the drug should be prescribed to this population after estimating the potential risks and benefits of the drug and the patient's potential need for this drug.

Breastfeeding

No data shows Metaxalone or its metabolite excreted in human or animal milk, the effects on milk production, or the effects produced on breastfeeding infants. Therefore, doctors must consider the health and developmental benefits of breastfeeding and the mother’s potential need for the drug and associated adverse effects on the infant or the underlying maternal conditions affecting the baby.

Renal Impairment

The drug is contraindicated in this population as well. Careful monitoring is advised while prescribing Metaxalone in patients with renal impairment (mild to moderate). The drug goes through renal excretion. However, the effects of renal impairment on the pharmacokinetics of the drug are not known.

Hepatic Impairment

The drug is contraindicated in this population, and therefore, Metaxalone should be cautiously used in people with hepatic impairment (mild to moderate) with continuous monitoring. The drug undergoes extensive hepatic metabolism; however, the effects of hepatic impairment on the drug's pharmacokinetics are unknown.

Geriatric Use

Clinical studies on the drug lack sufficient data on this population group and, thus, do not show if this drug works differently in the geriatric population. The safety and effectiveness of Metaxalone are not established in this population group. Therefore, senior people are more at risk of developing central nervous system (CNS) depression associated with the drug.

Pediatric Use

The safety and effectiveness of the drug are established for children aged 12 years and above. The drug is not recommended for children below 12 years of age.