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Dantrolene for chronic muscle spasm


When you first start taking dantrolene, your doctor will give you a small dose (one capsule a day). Your dose will then be increased at weekly intervals.

Dantrolene can make you feel sleepy or dizzy. It can slow your reactions, so please take care if you are using tools or machines, or if you drive.

Dantrolene can cause liver damage in a few people. Signs of this are loss of appetite, tiredness, itching, jaundice, and sickness. Let your doctor know straightaway if you develop any of these, so that it can be investigated.

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About dantrolene

Type of medicine

A muscle relaxant

Used for

Muscle spasms and spasticity

Also called


Available as


Dantrolene belongs to a group of medicines called muscle relaxants. Muscle relaxants are medicines that are used to prevent or reduce muscle spasms and spasticity. Muscle spasms occur when there is an uncontrolled (involuntary) contraction of a group of muscles. This often causes pain and discomfort. Spasticity occurs when the muscles contract tightly and then become stiff and harder to use.

Dantrolene is used to relieve muscle spasms and spasticity which result from long-term conditions affecting the nervous system, such as multiple sclerosis, motor neurone disease or cerebral palsy, or following long-term injuries to the head or back. It works by causing the muscles to relax and this reduces pain and discomfort.

Before taking dantrolene

Some medicines are not suitable for people with certain conditions, and sometimes a medicine may only be used if extra care is taken. For these reasons, before you start taking dantrolene it is important that your doctor knows:

  • If you have any problems with the way your liver works, or if you have a heart condition, or if you have any difficulties with your breathing.

  • If you are pregnant or breastfeeding.

  • If you are taking or using any other medicines. This includes any medicines you are taking which are available to buy without a prescription, as well as herbal and complementary medicines.

  • If you have ever had an allergic reaction to a medicine.

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How to take dantrolene

  • Before you start the treatment, read the manufacturer's printed information leaflet from inside the pack. It will give you more information about dantrolene and will provide you with a full list of the side-effects which you may experience from taking it.

  • When starting the treatment, your doctor will give you a small dose (usually one 25 mg capsule daily) and will then gradually increase your dose at weekly intervals. This allows your doctor to make sure that you have the dose that helps your condition but avoids any unwanted symptoms.

  • Swallow the capsule with a drink of water. You can take dantrolene either before or after a meal.

  • Continue to take dantrolene exactly as your doctor tells you to. Your dose will be printed on the label of the pack to remind you about what your doctor said to you. Once you are established on a regular dose of dantrolene, try to take your doses at the same times of day each day, as this will help you to remember to take them.

  • If you do forget to take a dose, take it when you remember unless your next dose is about due. If it is nearly time for your next dose then take the next dose when it is due but leave out the forgotten dose. Do not take two doses together to make up for a missed dose.

Getting the most from your treatment

  • Try to keep your regular appointments with your doctor. This is so your doctor can check on your progress, as it may take a few weeks before you begin to feel the benefit from dantrolene.

  • If after six weeks or so you don't feel you are improving, please speak with your doctor about this, as your treatment could need reviewing.

  • Dantrolene can cause drowsiness and may affect your reactions. Be careful this does not put you at risk if you are using any tools or machines, or if you drive.

  • It is recommended that you do not drink alcohol while you are on dantrolene. This is because the risk of side-effects, such as feeling sleepy and dizzy, is increased.

  • Treatment with dantrolene is usually long-term unless you experience an adverse event. Continue to take the capsules unless your doctor tells you otherwise. If your muscle spasms increase or if you have difficulty doing things because you feel your muscles have become weak, let your doctor know about this, as your dose may need adjusting.

  • If you are having an operation or dental treatment, tell the person carrying out the treatment which medicines you are taking.

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Can dantrolene cause problems?

Along with their useful effects, most medicines can cause unwanted side-effects although not everyone experiences them. The table below contains some of the most common ones associated with dantrolene. You will find a full list in the manufacturer's information leaflet supplied with your medicine. The unwanted effects often improve as your body adjusts to the new medicine but speak with your doctor or pharmacist if any of the following continue or become troublesome.

Common dantrolene side-effects (these affect fewer than 1 in 10 people)

What can I do if I experience this?

Feeling dizzy, sleepy, or very tired

If this happens, do not drive and do not use tools or machines. Do not drink alcohol


Drink plenty of water to replace the lost fluids. If the diarrhoea is severe, speak with your doctor about this as you may need to stop taking dantrolene for a while

Feeling sick (nausea) or being sick (vomiting), tummy (abdominal) pain

Eat simple meals - avoid rich or spicy foods


Drink plenty of water and ask your pharmacist to recommend a suitable painkiller. If the headaches continue, let your doctor know

Loss of appetite, skin rash or acne, speech or sight difficulties, high temperature (fever), chills, difficulties breathing, fits, and inflammation of the lining around the heart (sometimes with fluid in the lungs)

If you are concerned about any of these, speak with your doctor for advice

Important: your doctor will discuss with you the possibility that dantrolene can cause damage to your liver. If you experience any of the following you should let your doctor know straightaway so that it can be investigated:

  • Loss of appetite

  • Extreme tiredness

  • Dark urine

  • Itching

  • Yellowing of your skin or the whites of your eyes (jaundice)

  • Constantly feeling sick (nausea) or being sick (vomiting)

  • Pain in your tummy (abdomen)

These are signs that your liver could be being damaged and your doctor will want you to have a blood test to check for this.

If you experience any other symptoms which you think may be due to this medicine, discuss them with your doctor or pharmacist.

How to store dantrolene

  • Keep all medicines out of the reach and sight of children.

  • Store in a cool, dry place, away from direct heat and light.

Important information about all medicines

Important information about all medicines

Never take more than the prescribed dose. If you suspect that you or someone else might have taken an overdose of this medicine, go to the accident and emergency department of your local hospital. Take the container with you, even if it is empty.

This medicine is for you. Do not give it to other people even if their condition appears to be the same as yours.

If you buy any medicines, check with a pharmacist that they are suitable to take with your other medicines.

Do not keep out-of-date or unwanted medicines. Take them to your local pharmacy which will dispose of them for you.

If you have any questions about this medicine ask your pharmacist.

Report side effects to a medicine or vaccine

If you experience side effects, you can report them online through the Yellow Card website.

Further reading and references

Article history

The information on this page is written and peer reviewed by qualified clinicians.

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