Reviewed on 1/31/2022

What Is Dantrolene and How Does It Work?

Dantrolene is a prescription medication used to treat Malignant Hyperthermia (per MHAUS), Malignant Hyperthermia Prevention, and Spasticity

What Are Dosages of Dantrolene?

Adult and pediatric dosage


  • 25mg
  • 50mg
  • 100mg

Powder for injection

  • 20mg/vial (Dantrium, Revonto)
  • 250mg/vial (Ryanodex)

Malignant Hyperthermia (per MHAUS)

Adult and pediatric dosage

  • 2.5 mg/kg rapid IV bolus, repeat as needed
  • Sometimes over 10mg/kg (cumulative dose) is necessary (up to 30 mg/kg)
  • Maintenance: 1 mg/kg IV every 4-6 hours or 0.25 mg/kg/hr IV infusion
  • Monitor overnight in hospital for 24-48 hours

Malignant Hyperthermia, Prevention

Adult and pediatric dosage

NOT recommended by MHAUS

  • 1-3 days before surgery: 4-8 mg/kg/day orally divided every 6 hours
  • 75 minutes before anesthesia: 2.5 mg/kg IV once over 60 minutes; administer additional doses as needed


Adult dosage

  • 25 mg orally once daily for 7 days, then
  • 25 mg orally every 8 hours for 7 days, then
  • 50 mg orally every 8 hours for 7 days, then
  • 100 mg orally every 8 hours, not to exceed 100 mg orally every 6 hours
  • Discontinue if no benefits within 6-7 weeks

Pediatric dosage

  • Monitor: LFTs, bilirubin

Children younger than 5 years of age: 

  • 0.5 mg/kg orally once daily for 7 days, then 
  • 0.5 mg/kg orally every 8 hours for 7 days, then 
  • 1 mg/kg orally every 8 hours for 7 days, then 
  • 2 mg/kg orally every 8 hours, not to exceed 100 mg orally every 6 hours

Children older than 5 years of age:

  • Initial: 1 mg/kg/day orally divided every 12 hours
  • Maximum maintenance: 12 mg/kg/day orally divided every 6 hours
  • Not to exceed 3 mg/kg orally every 6-12 hours or 400 mg/24 hours orally

Dosage Considerations – Should be Given as Follows: 

  • See "Dosages."


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What Are Side Effects Associated with Using Dantrolene?

Common side effects of Dantrolene include:

  • drowsiness, 
  • dizziness, 
  • weakness, 
  • tiredness, 
  • nausea, 
  • diarrhea, 
  • headache, 
  • constipation, 
  • trouble speaking, and
  • drooling

Serious side effects of Dantrolene include:

  • hives, 
  • difficulty breathing, 
  • swelling of the face, lips, tongue, or throat, 
  • vision changes, 
  • black or tarry stools, 
  • vomit that looks like coffee grounds, 
  • mental or mood changes, 
  • trouble swallowing, 
  • difficulty urinating, 
  • severe and persistent constipation, 
  • seizures, 
  • fast heartbeat, 
  • easy bruising, 
  • unusual bleeding, 
  • fever, 
  • chills, 
  • persistent sore throat
  • chest pain, 
  • swelling of the ankles, and feet, and
  • severe dizziness

Rare side effects of Dantrolene include:

  • none 
This is not a complete list of side effects and other serious side effects or health problems may occur as a result of the use of this drug. Call your doctor for medical advice about serious side effects or adverse reactions. You may report side effects or health problems to FDA at 1-800-FDA-1088.

What Other Drugs Interact with Dantrolene?

If your medical doctor is using this medicine to treat your pain, your doctor or pharmacist may already be aware of any possible drug interactions and may be monitoring you for them.  Do not start, stop, or change the dosage of any medicine before checking with your doctor, health care provider or pharmacist first.

  • Dantrolene has severe interactions with the following drugs:
  • Dantrolene has serious interactions with at least 21 other drugs. 
  • Dantrolene has moderate interactions with at least 174 other drugs. 
  • Dantrolene has minor interactions with the following drugs:

This information does not contain all possible interactions or adverse effects. Visit the RxList Drug Interaction Checker for any drug interactions. Therefore, before using this drug, tell your doctor or pharmacist of all the drugs you use. Keep a list of all your medications with you, and share the list with your doctor and pharmacist. Check with your physician if you have health questions or concerns.

What Are Warnings and Precautions for Dantrolene?


  • NO CONTRAINDICATIONS for IV use in MH management/prophylaxis
  • Hypersensitivity
  • Impaired hepatic, cardiac or pulmonary function
  • Upper motor neuron disorder
  • Patients in whom spasticity is utilized to maintain upright posture and balance

Effects of drug abuse

  • None

Short-Term Effects

  • See “What Are Side Effects Associated with Using Dantrolene?”

Long-Term Effects

  • See “What Are Side Effects Associated with Using Dantrolene?”


  • Possibility of severe hepatotoxicity
  • Risk of muscle weakness
  • Risk of photosensitivity reactions
  • Females, over 35 years, receiving other drugs, history of liver disease
  • Not indicated in muscle spasms due to rheumatic disorder or musculoskeletal trauma
  • Ineffective in ALS
  • Use caution when administering oral therapy in patients with severely impaired cardiac function resulting from myocardial disease
  • Use caution when administering oral therapy in patients with impaired pulmonary function
  • In combination with calcium channel blockers IV dantrolene may increase risk for hyperkalemia and cardiac arrest (combination not recommended)
  • Severely impaired cardiac function due to myocardial disease
  • Associated with pleural effusion with associated eosinophilia

Pregnancy and Lactation

  • Available data on use in pregnant women are insufficient to evaluate for a drug-associated risk of major birth defects, miscarriage, or adverse maternal or fetal outcomes; the drug readily crosses placenta; however, no serious adverse events reported in neonate following maternal administration of drug prior to delivery; there are risks to pregnant woman and fetus associated with untreated malignant hyperthermia
  • Malignant hyperthermia is a medical emergency which can be fatal for the pregnant woman and fetus if left untreated; life-sustaining therapy should not be withheld due to pregnancy
  • Labor or Delivery
    • In uncontrolled study, 100 mg per day of prophylactic oral dantrolene sodium was administered to term pregnant patients awaiting labor and delivery; the drug readily crosses placenta, with maternal and fetal whole blood levels approximately equal at delivery; neonatal levels then fell approximately 50% per day for 2 days before declining sharply; no neonatal respiratory and neuromuscular side effects were observed in this study. 
    • Lactation: Dantrolene is reported to be present in human milk following intravenous administration over 3 days; there are no data on effects on breastfed infant or effects on milk production; because of potential for serious adverse reactions in breastfed infant, including respiratory depression and muscle weakness, advise patients that breastfeeding is not recommended during treatment and for 3 days after last dose
    • A lactating woman should interrupt breastfeeding and pump and discard breast milk during treatment and for 3 days after the last dose administered.


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Medscape. Dantrolene.


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