Boots WebMD Partners in Health
Return To Boots

Medicines & treatments centre

Terms Of Use


Brand Name(s) : Dantrium, Dantrium Intravenous
Side Effects


Dantrolene should be used with caution in: patients who have heart or lung function problems; patients who have liver problems or notice signs or symptoms of liver toxicity (e.g. discoloured faeces, intense itching, jaundice, anorexia, nausea, vomiting during therapy); patients who are elderly.

It should not be used in: patients who are allergic to dantrolene or any of the ingredients in the product; patients who have known liver function problems; patients who have acute skeletal muscle spasm (your muscles go rigid suddenly); patients who need spasticity to stand up, walk or cope with daily activities; children.

Also see list of precautions and interactions


Store below 30°C


What is it used for?

  • Dantrolene is used to treat muscle tightness and cramping (spasms) caused by certain nerve disorders such as spinal cord injury, stroke, cerebral palsy and multiple sclerosis.
  • It is a muscle relaxant.
  • It is used to relax muscles.
  • In general this drug is used to treat the symptoms of severe, long term muscle stiffness in adults and also malignant hyperthermia (high fever triggered by exposure to certain drugs used for general anaesthesia).
  • Benefits of being on this drug can include helping to reduce muscle pain and stiffness and improves your ability to move around.

Listed below are the typical uses of dantrolene:

  • Treatment of chronic, spasticity of skeletal muscle in adults
  • Treatment of malignant hyperthermia (high fever)

On occasion your doctor may prescribe this medicine to treat a condition not on the above list.


How often do I take it?

  • This medication is available as a capsule or as an intravenous (to go into the vein) injection.
  • Take the capsule by mouth with water, as directed by your doctor. For the treatment of long-term muscle tightness and spasms, your doctor may slowly increase your dose to lower your chance of side effects until the right dose for you is determined. The manufacturer recommends that you do not take more than 400 milligrams per day
  • The intravenous formulation may need to be taken more or less frequently, but your doctor will advise you. This formulation is used to treat malignant hyperthermia.
  • Use this medication regularly in order to get the most benefit from it.
  • Remember to use it at the same time each day - unless specifically told otherwise by your doctor.
  • It may take a few weeks before the full benefit of this drug takes effect. However, in view of the potential for hepatotoxicity (causing liver damage) in long term use, if no observable benefit is gained from taking dantrolene after 6 to 8 weeks, your doctor will tell you to stop taking it.
  • Certain medical conditions may require different dosage instructions as directed by your doctor.

What dose?

  • Dosage is based on your age, gender, medical condition, response to therapy, and use of certain interacting medicines.

Do I need to avoid anything?

  • Patients should be advised not to drive a motor vehicle or to undertake potentially dangerous work until dantrolene therapy has been stabilised, because some patients experience drowsiness and dizziness. The effects of alcohol are enhanced, so limit your alcohol intake. Consult your doctor or pharmacist for more details.

When can I stop?

  • It is important to continue taking this medication even if you feel well, unless your doctor tells you to stop.


If any of these persist or you consider them severe then inform your doctor or pharmacist

Tell your doctor immediately if you develop any of the following symptoms:

  • Hepatotoxicity (such as discoloured faeces, generalized pruritus, jaundice, anorexia, nausea, vomiting)
  • Sunburn (sun sensitivity)
  • Vision changes
  • Vomit that looks like coffee grounds
  • Mental/mood changes
  • Trouble swallowing
  • Problems with urination
  • Severe/ persistent constipation
  • Seizures
  • Fast heartbeat
  • Easy bruising/ bleeding
  • Signs of infection (e.g., fever, chills, persistent sore throat)
  • Chest pain
  • Swelling of the ankles/feet
  • Trouble breathing

Remember that your doctor has prescribed this medication because he or she has judged that the benefit to you is greater than the risk of side effects. Many people using this medication do not have serious side effects.

A serious allergic reaction to this drug is unlikely, but seek immediate medical attention if it occurs. Symptoms of a serious allergic reaction include: rash, itching/swelling (especially of the face/tongue/throat), dizziness, trouble breathing.

This is not a complete list of possible side effects. If you notice other effects not listed above, contact your doctor or pharmacist.

The Yellow Card Scheme allows you to report suspected side effects from any type of medicine (which includes vaccines, herbals and over the counter medicines) that you are taking. It is run by the medicines safety watchdog called the Medicines and Healthcare products Regulatory agency (MHRA). Please report any suspected side effect on the Yellow Card Scheme website.


Before taking dantrolene, tell your doctor or pharmacist if you are allergic to it; or to other muscle relaxants; or if you have any other allergies.

This medication should not be used if you have certain medical conditions. Before using this medicine, consult your doctor or pharmacist if you: use muscle stiffness (spasticity) to sustain an upright posture and balance inmovement; have liver problems (such as hepatitis or hepatic dysfunction or cirrhosis); have acute skeletal muscle spasms; are a child.

Before using this medication, tell your doctor or pharmacist your medical history, especially any of the following: breathing problems (e.g. chronic obstructive pulmonary disease); heart problems.

Liver function tests should be performed frequently before starting and during dantrolene therapy as the risk of liver toxicity appears to be greater in: females; patients over 30 years old; patients taking other medication; women using oral oestrogen contraception.

Before having surgery, tell your doctor or dentist that you are taking this medication.

Does alcohol intake affect this drug?

  • Avoid taking alcohol with this medicine as it may enhance side effects, such as dizziness and drowsiness.

The elderly: A similar dosage regime to adults can be used with the elderly; however caution is advised when liver function is impaired.

Pregnancy and breastfeeding - please ensure you read the detailed information below


Dantrolene is not safe to take if you are, or are planning to become, pregnant, as it crosses the placenta. Ask your doctor or pharmacist if you have any doubts or questions about this.

It is sensible to limit use of medication during pregnancy whenever possible. However, your doctor may decide that the benefits outweigh the risks in individual circumstances and after a careful assessment of your specific health situation.

If you have any doubts or concerns you are advised to discuss the medicine with your doctor or pharmacist.


Dantrolene is not safe to take if you are breastfeeding, as it passes into breast milk.

It is sensible to limit use of medication during breastfeeding whenever possible. However, your doctor may decide that the benefits outweigh the risks in individual circumstances and after a careful assessment of your specific health situation.

If you have any doubts or concerns you are advised to discuss the medicine with your doctor or pharmacist.


Before using this medicine, tell your prescriber of all the medicines you are taking including prescription medicines and medicines you have bought over the counter without a prescription. Tell your prescriber if you are taking vitamins or complementary remedies such as herbal products, as these can also interact with medicines.

If you are taking more than one medicine, these may interact with each other. Your prescriber may decide to use medicines which interact with each other if the benefit outweighs the risks. In these cases, the dose of your medicines may need to be adjusted or you may be monitored more closely.

The following medicines may interact with dantrolene:

  • Oestrogen (found in most oral contraceptive pills and hormone replacement therapy)
  • Medicines used for anxiety, such as diazepam, lorazepam or temazepam
  • Medicines used to treat abnormal heartbeat, angina or high blood pressure (e.g. products containing verapamil)
  • Products normally used to help doctors anaesthetise patients (e.g. products containing vecuronium)
  • Medicines for high blood pressure and angina called calcium channel blockers

This information does not contain all possible interactions. Therefore, tell your prescriber of all the products you are using before taking this medicine.

If you have a question or want to discuss anything about your medicine, speak to your local pharmacist.


An overdose of dantrolene may cause: muscular weakness; alterations in the state of consciousness (e.g. lethargy, coma); vomiting; diarrhoea.

If you think you, or someone you care for, might have accidentally taken more than the recommended dose of dantrolene or intentional overdose is suspected, contact your local hospital, GP or if in England call 111. In Scotland call NHS 24. In Wales, call NHS Direct Wales. In the case of medical emergencies, always dial 999.


If you miss a dose, take it as soon as you remember. If it is near the time of the next dose, skip the missed dose and resume your usual dosing schedule. Do not double the dose to catch up.

Find a medication

Search by medication name for information on over-the-counter or prescription medications including side effects and interactions.
indicates detailed medicines information

Source: Selected from data included with permission and copyrighted by Boots UK Limited. This copyrighted material is sourced from a licensed data provider and is not for distribution, except as may be authorised by the applicable terms of use.
CONDITIONS OF USE: The information in this database is intended to supplement, not substitute for, the expertise and judgement of healthcare professionals. The information is not intended to cover all possible uses, directions, precautions, drug interactions or adverse events, nor should it be construed to indicate that use of a particular medicine is safe, appropriate or effective for you or anyone else. A healthcare professional should be consulted before taking any medicine, changing any diet, or discontinuing any course of treatment.

Search for a medicine or treatment

Search by medicine name or treatment for information including side effects and interactions.

Ex. Simvastatin, Ibuprofen, Amitriptyline Hydrochlorine

Popular slideshows & tools on BootsWebMD

How to help headache pain
rash on skin
Top eczema triggers to avoid
Causes of fatigue & how to fight it
Tips to support digestive health
woman looking at pregnancy test
Is your body ready for pregnancy?
woman sleeping
Sleep better tonight
Treating your child's cold or fever
bucket with cleaning supplies in it
Cleaning and organising tips
adult man contemplating
When illness makes it hard to eat
woman holding stomach
Understand this common condition
cold sore
What you need to know