Dantrolene may also be used before surgery for people at risk of malignant hyperthermia and for follow-up treatment of this condition.  Malignant hyperthermia is a syndrome of muscle rigidity and greatly increased body temperature that can be caused by a reaction to certain anaesthetics.  If left untreated, malignant hyperthermia can lead to death.

Your doctor may have suggested this medication for conditions other than the ones listed in these drug information articles.  If you have not discussed this with your doctor or are not sure why you are taking this medication, speak to your doctor.  Do not stop taking this medication without consulting your doctor. 

Do not give this medication to anyone else, even if they have the same symptoms as you do.  It can be harmful for people to take this medication if their doctor has not prescribed it.

How should I use this medication?

The usual starting dose for adults is 25 mg once daily.  The dose is then increased gradually until the best dose is found, based on individual response and needs.  The best dose is the lowest dose that will control the muscle spasms.  Most people respond to doses of 400 mg daily (given in divided doses, usually as 100 mg 4 times daily) or less.  Children's dosing is based on body weight.  Children should not be given doses higher than 100 mg 4 times daily.

Many things can affect the dose of a medication that a person needs, such as body weight, other medical conditions, and other medications.  If your doctor has recommended a dose different from the ones listed here, do not change the way that you are taking the medication without consulting your doctor.

It is important that this medication be taken on a regular schedule and exactly as prescribed by the doctor.  If you miss a dose of this medication, check with your health care professional.  Do not take a double dose to make up for a missed one.

What form(s) does this medication come in?

25 mg

Each opaque orange and brown capsule (opaque orange cap and opaque light tan to brown body), coded with 1 black bar and "DANTRIUM 25 mg 0149 0030", contains dantrolene sodium 25 mg.  Nonmedicinal ingredients: carnauba wax, edible black ink, FD&C Yellow No.  6, gelatin, iron oxide red, iron oxide yellow, lactose, magnesium stearate, starch, talc, titanium dioxide, and may contain one or more of the following: FD&C Blue No.  2, D&C Red No.  33.

100 mg

Each opaque orange and brown capsule (opaque orange cap and opaque light tan to brown body), coded with 3 black bars and "DANTRIUM 100 mg 0149 0033", contains dantrolene sodium 100 mg.  Nonmedicinal ingredients: carnauba wax, edible black ink, FD&C Yellow No.  6, gelatin, iron oxide red, iron oxide yellow, lactose, magnesium stearate, starch, talc, titanium dioxide, and may contain one or more of the following: FD&C Blue No.  2, D&C Red No.  33.

Some medications may have other generic brands available.  Always ask your doctor or pharmacist about the safety of switching between brands of the same medication.

Who should NOT take this medication?

Dantrolene should not be taken by anyone who:

is allergic to dantrolene or any of the ingredients of the medication

has active liver disease (such as hepatitis or cirrhosis)

has a particular type of muscle spasm (one that, in the doctor's opinion, may actually help increase or maintain the person's ability to function)

has poor lung function

What side effects are possible with this medication?

Many medications can cause side effects.  A side effect is an unwanted response to a medication when it is taken in normal doses.  Side effects can be mild or severe, temporary or permanent.  The side effects listed below are not experienced by everyone who takes this medication.  If you are concerned about side effects, discuss the risks and benefits of this medication with your doctor.

The following side effects have been reported by at least 1% of people taking this medication.  Many of these side effects can be managed, and some may go away on their own over time.

Contact your doctor if you experience these side effects and they are severe or bothersome.  Your pharmacist may be able to advise you on managing side effects.

More common:

diarrhea (mild)

dizziness or lightheadedness

drowsiness

general feeling of discomfort or illness

muscle weakness

nausea or vomiting

unusual tiredness

Less common:

abdominal or stomach cramps or discomfort

blurred or double-vision or any change in vision

chills and fever

constipation (mild)

difficulty swallowing

frequent urge to urinate or uncontrolled urination

headache

loss of appetite

slurring of speech or other speech problems

sudden decrease in amount of urine

trouble sleeping

unusual nervousness

Although most of the side effects listed below don't happen very often, they could lead to serious problems if you do not seek medical attention.

Check with your doctor as soon as possible if any of the following side effects occur:

Less common:

bloody or dark urine

chest pain

confusion

constipation (severe)

depression

diarrhea (severe)

difficult urination

skin rash, hives, or itching

yellow eyes or skin

Stop taking the medication and seek immediate medical attention if any of the following occur:

Less common:

convulsions (seizures)

pain, tenderness, changes in skin colour, or swelling of foot or leg

shortness of breath or slow or troubled breathing

Are there any other precautions or warnings for this medication?

Before you begin using a medication, be sure to inform your doctor of any medical conditions or allergies you may have, any medications you are taking, whether you are pregnant or breast-feeding, and any other significant facts about your health.  These factors may affect how you should use this medication.

Drowsiness/reduced alertness: This medication may temporarily cause drowsiness, which may impair your ability to drive or operate machinery.  These effects should only last about a week.  Avoid hazardous tasks for the first week of treatment.

Heart function: While taking this medication, people with heart disease should be closely monitored by their doctors.

Liver injury: Dantrolene capsules may be toxic to the liver, or worsen existing liver damage.  The risk of liver injury is greater for women, people over 35 years of age, and people taking other medications.  If you have liver disease, talk to your doctor about whether you should use this medication.  People using this medication will likely have liver tests before and during use.

Pregnancy: This medication should not be used during pregnancy unless the benefits outweigh the risks.  If you are or may be pregnant, discuss with your doctor the benefits and risks of using this medication.

Breast-feeding: This medication should not be used by women who are breast-feeding.

Children: The safety and effectiveness of using this medication have not been established for children under 5 years of age.

What other drugs could interact with this medication?

Tell your doctor or prescriber about all prescription, over-the-counter (non-prescription), and herbal medications that you are taking.  Also tell them about any supplements you take.  Since caffeine, alcohol, the nicotine from cigarettes, or street drugs can affect the action of many medications, you should let your prescriber know if you use them.  Depending on your specific circumstances, your doctor may want you to:

stop taking one of the medications,

change one of the medications to another,

change how you are taking one or both of the medications, or

leave everything as is. 

An interaction between two medications does not always mean that you must stop taking one of them.  In many cases, interactions are intended or are managed by close monitoring.  Speak to your doctor about how any drug interactions are being managed or should be managed.

The contents of this site are for informational purposes only and are meant to be discussed with your physician or other qualified health care professional before being acted on.  Never disregard any advice given to you by your doctor or other qualified health care professional.  Always seek the advice of a physician or other licensed health care professional regarding any questions you have about your medical condition(s) and treatment(s).  This site is not a substitute for medical advice.

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