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Overview: Metaxalone is used short-term to relieve muscle, bone, and joint pain. It seems to relax muscles by affecting nerve activity in the spinal cord. Common side effects include dizziness and drowsiness. Do not drive or do other activities that require alertness or coordination until you know how metaxalone affects you.

Uses

What is metaxalone used for?

Metaxalone is commonly used for discomfort related to short-term, painful musculoskeletal conditions. These are conditions that affect the muscles, bones, and joints of your body.

Metaxalone may also be used for other conditions as determined by your healthcare provider.

How does metaxalone work (mechanism of action)?

Metaxalone may work by slowing down your nervous system, which leads to muscle relaxation and relief.

How is metaxalone supplied (dosage forms)?

Dosage forms and strengths

  • 400 mg, 800 mg oral tablets

How should I store metaxalone?

Metaxalone should be stored at room temperature, between 68 F to 77 F (20 C to 25 C). It can be exposed to temperatures between 59 F to 86 F (15 C to 30 C) for shorter periods of time, such as when transporting it. Store in a cool, dry place.

Side Effects

What are the most common side effects of metaxalone?

The most common side effects of metaxalone are listed below. Tell your healthcare provider if you have any of these side effects that bother you.

  • Nausea and vomiting
  • Drowsiness
  • Dizziness
  • Headache
  • Nervousness
  • Irritability
  • Upset stomach

There may be other side effects of metaxalone that are not listed here. Contact your healthcare provider if you think you are having a side effect of a medicine. In the U.S., you can report side effects to the FDA at www.fda.gov/medwatch or by calling 800-FDA-1088. In Canada, you can report side effects to Health Canada at www.health.gc.ca/medeffect or by calling 866-234-2345.

What are the serious side effects of metaxalone?

While less common, the most serious side effects of metaxalone are described below, along with what to do if they happen.

Severe Allergic Reactions. Metaxalone may cause allergic reactions, which can be serious. Stop taking metaxalone and get help right away if you have any of the following symptoms of a serious allergic reaction.

  • Breathing problems or wheezing
  • Racing heart
  • Fever or general ill feeling
  • Swollen lymph nodes
  • Swelling of the face, lips, mouth, tongue, or throat
  • Trouble swallowing or throat tightness
  • Itching, skin rash, or pale red bumps on the skin called hives
  • Nausea or vomiting
  • Dizziness, feeling lightheaded, or fainting
  • Stomach cramps
  • Joint pain

Central Nervous System (CNS) Depression. Metaxalone may slow down your central nervous system (CNS), which controls many important functions throughout the body. Call your healthcare provider right away if you have any of the following symptoms of CNS depression.

  • Confusion
  • Excessive sleepiness or trouble staying awake
  • Memory problems
  • Slow or shallow breathing
  • Slowed response or reaction time
  • Slurred speech

Serotonin Syndrome. Serotonin syndrome is when there is too much of a substance called serotonin in your body. Metaxalone can cause serotonin syndrome when it is taken alone or with other medicines that affect serotonin. This condition can be life-threatening. Get emergency help if you have any of the following symptoms of serotonin syndrome.

  • Sweating, fever, or flushing
  • Confusion
  • Feeling agitated or restless
  • Seeing or hearing unusual things
  • Dizziness
  • Fast or racing heartbeat
  • Nausea, vomiting, or diarrhea
  • Muscle twitching, stiffness, or tremor
  • Seizures

Warnings & Precautions

Who should not use metaxalone?

Allergies to Ingredients. People who are allergic to any of the following should not take metaxalone.

  • Metaxalone
  • Any of the ingredients in the specific product dispensed

Your pharmacist can tell you all of the ingredients in the specific metaxalone products they stock.

Kidney Problems. Metaxalone should not be taken if your kidneys are not working as well as they should be. If there is a concern about the health of your kidneys, your healthcare provider may do tests to determine if they are working well enough to take this medicine.

Liver Problems. Metaxalone should not be taken if your liver is not working as well as it should be. If there is a concern about the health of your liver, your healthcare provider may do tests to determine if it is working well enough to take this medicine.

Anemia. Metaxalone should not be taken if you have a tendency to anemia, which is when you have low levels of red blood cells. Anemia can be caused by many things, including medicines. Tell your healthcare provider if you have had any type of anemia, including hemolytic anemia.

What should I know about metaxalone before using it?

Do not take metaxalone unless it has been prescribed to you by a healthcare provider. Take it as prescribed.

Do not share metaxalone with other people, even if they have the same condition as you. It may harm them.

Keep metaxalone out of the reach of children.

Metaxalone is usually used with rest, physical therapy, or other measures to help with discomfort related to painful musculoskeletal conditions.

Metaxalone can affect your alertness or coordination. Do not drive or do other activities that require alertness or coordination until you know how metaxalone affects you.

People who are aged 65 years and older can be at greater risk for some side effects from metaxalone. Talk to your healthcare provider about your risks if you are 65 years and older.

What should I tell my healthcare provider before using metaxalone?

Tell your healthcare provider about all of your health conditions and any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using. This will help them determine if metaxalone is right for you.

In particular, make sure that you discuss any of the following.

Current and Past Health Conditions. Tell your healthcare provider if you have any of the following.

  • Kidney problems
  • Liver problems

Other Medicines and Supplements. Metaxalone may interact with other medicines and supplements. Before taking metaxalone, tell your healthcare provider about any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using. See the Interactions section for more details.

Pregnancy. It is not known if or how metaxalone could affect pregnancy or harm an unborn baby. Tell your healthcare provider if you are or plan to become pregnant.

Breastfeeding. It is not known if metaxalone passes into breast milk. Tell your healthcare provider if you are breastfeeding or plan to breastfeed. Your healthcare provider will advise you if you should take metaxalone while breastfeeding.

Interactions

Does metaxalone interact with foods or drinks?

Taking metaxalone with food may enhance certain side effects, such as drowsiness and dizziness. If you have questions about the best time to take metaxalone, ask your pharmacist or other healthcare provider. 

Do not drink alcohol while taking metaxalone. The risk of drowsiness and dizziness may be increased if you drink alcohol with it.

Does metaxalone interact with other medicines (drug interactions)?

Always tell your healthcare provider about any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using.

In particular, make sure that you discuss if you are using any of the following before taking metaxalone.

  • A benzodiazepine, such as clonazepam (Klonopin), diazepam (Valium and others), or lorazepam (Ativan and others), which is a medicine used for anxiety, muscle spasms, or seizures
  • An opioid, such as oxycodone, morphine, codeine, or fentanyl, which is a medicine used for certain types of pain
  • A tricyclic antidepressant, such as amitriptyline, nortriptyline, or protriptyline, even if it is not used for depression
  • A selective serotonin reuptake inhibitor (SSRI) or serotonin norepinephrine reuptake inhibitor (SNRI), which is a medicine commonly used for anxiety and depression
  • A monoamine oxidase inhibitor (MAOI), which is a medicine usually used for depression or Parkinson’s disease
  • A type of medicine called a triptan, such as sumatriptan (Imitrex and others), eletriptan (Relpax), and others, which is commonly used to treat migraines
  • Mirtazapine (Remeron, Remeron Soltab), which is a medicine commonly used for depression
  • Trazodone, which is a medicine commonly used for depression, difficulty sleeping, and others
  • Tramadol (Qdolo, and others), which is a medicine commonly used for certain types of pain
  • Linezolid (Zyvox), which is a medicine commonly used for certain infections
  • Any other medicine that causes dizziness and sleepiness, such as prescription pain medicines, sleep medicines, and medicines for anxiety

This may not be a complete list of medicines that can interact with metaxalone. Always check with your healthcare provider.

Does interact with other drugs you are taking?

Enter your medication into the WebMD interaction checker

Overdose/Missed Dose

What should I do if I accidentally use too much metaxalone?

If you or someone else has used too much metaxalone, get medical help right away, call 911, or contact a Poison Control center at 800-222-1222.

What should I do if I miss a dose of metaxalone?

If you miss a dose, take it as soon as you remember. If it is almost time for your next dose, skip the missed dose and only take the next dose. Do not take double or extra doses.