Dantrolene is used to treat spasticity (muscle stiffness and tightness) or muscle spasms associated with spinal cord injuries, stroke, multiple sclerosis, or cerebral palsy. It is also used to prevent, treat, or reduce the risk of malignant hyperthermia (a disorder that causes a fast rise in body temperature and muscle contractions), Dantrolene is in a class of medications called skeletal muscle relaxants. Dantrolene acts on the spinal cord nerves to treat spasticity and to prevent and treat malignant hyperthermia.

Side Effects Of Dantrolene

Dantrolene may cause side effects. Tell your doctor if any of these symptoms are severe or do not go away:

  • muscle weakness
  • dizziness
  • diarrhea
  • fatigue

In addition to the symptoms mentioned in the WARNINGS AND PRECAUTIONS section, if you experience any of the following symptoms, call your doctor immediately:

  • seizures
  • difficulty breathing or slow, shallow breathing

Warnings & Precautions

Before taking dantrolene:

  • tell your doctor and pharmacist if you are allergic to dantrolene, any other medications, or any of the ingredients in dantrolene capsules. Ask your pharmacist for a list of the ingredients.
  • tell your doctor and pharmacist what other prescription and nonprescription medications, vitamins, nutritional supplements, and herbal products you are taking or plan to take. Be sure to mention any of the following: antidepressants; medications for anxiety; calcium channel blockers such as amlodipine (Norvasc), diltiazem (Cardizem, Dilacor, Tiazac, others), felodipine (Plendil), isradipine (DynaCirc), nicardipine (Cardene), nifedipine (Adalat, Procardia), nimodipine (Nimotop), nisoldipine (Sular), and verapamil (Calan, Verelan); estrogen-containing contraceptives (birth control pills, patches, rings, and injections); or estrogen replacement therapy; medications for mental illness; medications for seizures; sedatives; sleeping pills; or tranquilizers. Your doctor may need to change the doses of your medications or monitor you carefully for side effects.
  • tell your doctor if you have or have ever had muscle spasms from a rheumatic disorder, or heart or lung disease.
  • tell your doctor if you are pregnant, plan to become pregnant, or are breast-feeding. If you become pregnant while taking dantrolene, call your doctor immediately.
  • if you are having surgery, including dental surgery, tell the doctor or dentist that you are taking dantrolene.
  • you should know that dantrolene may make you drowsy. Do not drive a car or operate machinery until you know how this medication affects you.
  • ask your doctor about the safe use of alcoholic beverages while you are taking dantrolene. Alcohol can make the side effects of dantrolene worse.
  • you should plan to avoid unnecessary or prolonged exposure to sunlight and to wear protective clothing, sunglasses, and sunscreen. Dantrolene may make your skin sensitive to sunlight.

Dosage Of Dantrolene

Dantrolene comes as a capsule to take by mouth. When used to treat spasticity, it is usually taken once a day for 7 days and then increased gradually every 7 days to three to four times a day. When used to prevent malignant hyperthermia, it is usually given three to four times a day, starting 1 or 2 days before surgery. When used after a malignant hyperthermia crisis, it is usually given in 4 divided doses for 1 to 3 days. Follow the directions on your prescription label carefully, and ask your doctor or pharmacist to explain any part you do not understand. Take dantrolene exactly as directed. Do not take more or less of it or take it more often than prescribed by your doctor.

Your doctor will probably start you on a low dose of dantrolene for spasticity and gradually increase your dose, not more than once every 7 days. If your symptoms do not improve or get worse within 45 days of taking dantrolene, call your doctor.


Do not let anyone else take your medication. Ask your pharmacist any questions you have about refilling your prescription.

It is important for you to keep a written list of all of the prescription and nonprescription (over-the-counter) medicines you are taking, as well as any products such as vitamins, minerals, or other dietary supplements. You should bring this list with you each time you visit a doctor or if you are admitted to a hospital. It is also important information to carry with you in case of emergencies.


All information has been provided courtesy of MedLinePlus from the National Library of Medicine and from the FDA.