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Overview: Dantrolene is used for muscle spasms and to prevent very high body temperatures in certain people. It works by relaxing muscles and reducing spasms. Common side effects include drowsiness and dizziness. Serious side effects are rare, but can include liver damage. Notify your healthcare provider right away if you have nausea and vomiting or a reduced appetite.

Uses

What is dantrolene used for?

Dantrolene is commonly used for muscle spasticity, including muscle spasms due to certain conditions, such as spinal cord injury, stroke, cerebral palsy, and multiple sclerosis. This medicine may also be used to prevent or lessen very high body temperature (malignant hyperthermia) in certain people.

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

How does dantrolene work (mechanism of action)?

Dantrolene works by relaxing muscles and reducing muscle spasms in people with muscle spasticity.

How is dantrolene supplied (dosage forms)?

Brand and other names

  • Dantrium

Dosage forms and strengths

  • 25 mg, 50 mg, 100 mg oral capsules

How should I store dantrolene?

Store 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 dantrolene?

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

  • Drowsiness and dizziness (see below)
  • Weakness 
  • General feeling of being unwell, tired, or not having your usual energy 
  • Tiredness
  • Diarrhea

There may be other side effects of dantrolene 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 dantrolene?

While less common, the most serious side effects of dantrolene are described below, along with what to do if they happen. These side effects may vary depending on the condition that is being treated. Tell your healthcare provider if you have any of these side effects that bother you.

Severe Allergic Reactions. Dantrolene may cause allergic reactions, which can be serious. Stop taking dantrolene 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

Liver Damage. Liver damage, also called hepatotoxicity, can happen when taking dantrolene. Call your healthcare provider right away if you have any of the following symptoms of liver damage.

  • Nausea or vomiting
  • Stomach or belly pain
  • Fever
  • Weakness or unusual tiredness
  • Itching
  • Loss of appetite
  • Light-colored poop
  • Dark-colored urine (pee)
  • Your skin or the whites of your eyes turning yellowish in color (also called jaundice)

Drowsiness and Dizziness. Dantrolene can affect your alertness or coordination and cause dizziness and drowsiness. Do not drive or do other activities that require alertness or coordination until you know how dantrolene affects you.

Warnings & Precautions

Who should not use dantrolene?

Allergies to Ingredients. People who are allergic to any of the following should not use dantrolene.

  • Dantrium
  • Revonto
  • Ryanodex
  • Dantrolene
  • Any of the ingredients in the specific product dispensed

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

Liver Problems. Dantrolene should not be used 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 use this medicine.

Beneficial Muscle Stiffness. Dantrolene should not be used if your spasticity helps you to function such as walking or sitting upright. 

What should I know about dantrolene before using it?

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

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

Keep dantrolene out of the reach of children.

Dantrolene can make your skin more sensitive to light from the sun, sunlamps, and tanning beds. This is called photosensitivity. Exposure to this light can cause severe sunburns, blisters, and swelling. If you need to be in sunlight, wear sunscreen, a hat, and clothing that covers your skin.

People who are ages 65 years and older can be at greater risk for some side effects. Talk to your healthcare provider about your risks if you are in this age group.

What should I tell my healthcare provider before using dantrolene?

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 dantrolene 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.

  • Breathing or lung problems
  • Heart problems
  • Liver problems

Other Medicines and Supplements. Dantrolene may interact with other medicines and supplements. Before using dantrolene, 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 dantrolene could affect pregnancy or harm an unborn baby. Tell your healthcare provider if you are or plan to become pregnant.

Breastfeeding. Dantrolene 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 stop breastfeeding or stop dantrolene.

Interactions

Does dantrolene interact with foods or drinks?

There are no known interactions between dantrolene and foods or drinks.

It is unknown if drinking alcohol will affect dantrolene. The risk of drowsiness and dizziness may be increased if you drink alcohol while taking dantrolene.

Does dantrolene 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 using dantrolene.

  • Calcium channel blockers, such as verapamil (Verelan and others), which is a medicine used for high blood pressure and other conditions
  • Estrogen, such as certain birth control pills or estrogen patches, creams, rings, or vaginal suppositories 
  • A muscle relaxant, such as carisoprodol (Soma), cyclobenzaprine, metaxalone, or tizanidine (Zanaflex) 
  • 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 dantrolene. 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 dantrolene?

If you or someone else has used too much dantrolene, 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 dantrolene?

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.