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Dantrolene Side Effects

Medically reviewed by Last updated on Sep 27, 2022.


Commonly reported side effects of dantrolene include: drowsiness. Continue reading for a comprehensive list of adverse effects.

Applies to dantrolene: oral capsule. Other dosage forms:


Oral route (Capsule)

Dantrolene may cause hepatotoxicity, and symptomatic hepatitis (fatal and nonfatal) has been reported at various dose levels. Risk of hepatic injury appears to be greater in patients taking a higher dosage, in females, in patients older than 35 years, and in patients taking additional medication(s). Monitor hepatic function, including frequent determination of SGOT or SGPT, during therapy. Discontinue therapy after 45 days if there is no observable benefit.

Serious side effects of Dantrolene

Along with its needed effects, dantrolene may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention. Serious side effects are very rare when dantrolene is taken for a short time, for example, when it is used for a few days before, during, or after surgery or anesthesia to prevent or treat malignant hyperthermia. However, serious side effects may occur, especially when the medicine is taken for a long time.

Check with your doctor immediately if any of the following side effects occur while taking dantrolene:

Less common

  • Bloody or black, tarry stools
  • bloody or dark urine
  • bluish color changes in skin color
  • changes in speech
  • chest pain
  • confusion
  • constipation
  • convulsions (seizures)
  • decrease in frequency of urination
  • decrease in urine volume
  • difficult urination
  • difficulty in moving
  • difficulty in passing urine (dribbling)
  • difficulty in swallowing
  • fast, pounding, or irregular heartbeat or pulse
  • increased frequency of urination
  • increased urge to urinate during the night
  • joint pain
  • light-colored stools
  • lightheadedness
  • loss of bladder control
  • mental depression
  • muscle aching or cramping
  • muscle pains or stiffness
  • muscle spasm or jerking of all extremities
  • nausea and vomiting
  • pain in lower back
  • pain or burning while urinating
  • pain, tenderness, or changes in skin color
  • painful urination
  • severe stomach pain
  • shortness of breath
  • skin rash, hives, or itching
  • slow or troubled breathing
  • sudden decrease in amount of urine
  • sudden loss of consciousness
  • swelling of foot or leg
  • swollen joints
  • unusual tiredness or weakness
  • upper right abdominal pain
  • vomiting of blood or material that looks like coffee grounds
  • waking to urinate at night
  • yellow eyes or skin

Other side effects of Dantrolene

Some side effects of dantrolene may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. Also, your health care professional may be able to tell you about ways to prevent or reduce some of these side effects.

Check with your health care professional if any of the following side effects continue or are bothersome or if you have any questions about them:

More common

  • Diarrhea
  • dizziness
  • drowsiness
  • general feeling of discomfort or illness
  • muscle weakness

Less common

  • Abdominal or stomach cramps or discomfort
  • abnormal hair growth
  • acne-like rash
  • blurred or double vision or any change in vision
  • change in taste
  • chills and fever
  • disturbed color perception
  • excessive tearing
  • halos around lights
  • headache
  • itching skin
  • loss of appetite
  • night blindness
  • overbright appearance of lights
  • redness of skin
  • seeing double
  • skin rash, encrusted, scaly and oozing
  • sleeplessness
  • slurring of speech or other speech problems
  • sudden decrease in amount of urine
  • sweating
  • trouble in sleeping
  • tunnel vision
  • unable to sleep
  • unusual nervousness
  • weight loss

For Healthcare Professionals

Applies to dantrolene: intravenous powder for injection, oral capsule.


The more commonly reported adverse reactions have included loss of grip strength, leg weakness, drowsiness, dizziness, nausea, fatigue, diarrhea, thrombophlebitis, and injection site reactions.[Ref]


Common (1% to 10%): Hepatotoxicity, liver function test abnormalities

Frequency not reported: Jaundice, hepatitis, hepatic dysfunction including fatal hepatic failure[Ref]


Several reports of severe constipation and abdominal distention leading to functional obstruction have been reported. Diarrhea may be severe and may necessitate temporary withdrawal of therapy. If diarrhea recurs, therapy should probably be permanently discontinued.[Ref]

Common (1% to 10%): Dysphagia, nausea, vomiting, abdominal pain

Uncommon (0.1% to 1%): Constipation

Rare (less than 0.1%): Intestinal obstruction

Frequency not reported: Abdominal cramps, anorexia, alteration of taste, gastrointestinal bleeding, gastric irritation, diarrhea[Ref]


Postmarketing reports: Anaphylaxis


Common (1% to 10%): Infusion site pain

Postmarketing reports: Thrombophlebitis and tissue necrosis[Ref]


Frequency not reported: Abnormal hair growth, acne-like rash, eczematoid eruption, sweating, urticaria, rash, erythema[Ref]

Nervous system

Very common (10% or more): Somnolence (up to 17%), dysphonia (13%)

Common (1% to 10%): Headache, dizziness, seizure, lightheadedness, drooling[Ref]


Frequency not reported: Mental depression, mental confusion, insomnia, nervousness


Frequency not reported: Incontinence, increased urinary frequency, urinary retention, hematuria, crystalluria, nocturia, difficult urination and/or urinary retention, difficult erection


Very common (10% or more): Flushing

Common (1% to 10%): Pericarditis, atrioventricular block, tachycardia

Uncommon (0.1% to 1%): Exacerbation of preexisting cardiac insufficiency

Frequency not reported: Bradycardia, labile blood pressure, erratic blood pressure, heart failure, phlebitis[Ref]


Common (1% to 10%): Pleural effusion with associated eosinophilia

Rare (0.01% to 0.1%): -or- Rare (less than 0.1%):

Frequency not reported: Feeling of suffocation, respiratory depression, respiratory failure, dyspnea

Postmarketing reports: Pulmonary edema[Ref]

Pulmonary edema has developed during treatment of malignant hyperthermia; the contributory effect of the diluent volume and mannitol in these cases is not known.[Ref]


Common (1% to 10%): Muscular weakness, extremity pain

Frequency not reported: Myalgia, backache[Ref]


Frequency not reported: Aplastic anemia, leukopenia, lymphocytic lymphoma, thrombocytopenia[Ref]


Common (1% to 10%): Blurred vision

Frequency not reported: Visual disturbances, diplopia, excessive tearing[Ref]


Common (1% to 10%): Feeling abnormal

Frequency not reported: Chills, fever, general malaise[Ref]


Frequency not reported: Transient lowering of GFR and renal plasma flow following 8 weeks of oral therapy


1. Cerner Multum, Inc. "UK Summary of Product Characteristics." O 0

2. Cerner Multum, Inc. "Australian Product Information." O 0

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5. Chan CH "Dantrolene sodium and hepatic injury." Neurology 40 (1990): 1427-32

6. "Product Information. Dantrium (dantrolene)." Procter and Gamble Pharmaceuticals (2001):

7. Dykes MH "Evaluation of a muscle relaxant: dantrolene sodium (Dantrium)." JAMA 231 (1975): 862-4

8. Shaivitz SA "Letter: Dantrolene." JAMA 229 (1974): 1282-3

9. Pembroke AC, Saxena SR, Kataria M, Zilkha KD "Acne induced by dantrolene." Br J Dermatol 104 (1981): 465-8

10. Allen GC, Cattran CB, Peterson RG, Lalande M "Plasma levels of dantrolene following oral administration in malignant hyperthermia-susceptible patients." Anesthesiology 69 (1988): 900-4

11. Chyatte SB, Basmajian JV "Dantrolene sodium: long-term effects in severe spasticity." Arch Phys Med Rehabil 54 (1973): 311-5

12. Andrews LG, Muzumdar AS, Pinkerton AC "Letter: Hallucinations associated with dantrolene sodium therapy." Can Med Assoc J 112 (1975): 148

13. Petusevsky ML, Faling LJ, Rocklin RE, Snider GL, Merliss AD, Moses JM, Dorman SA "Pleuropericardial reaction to treatment with dantrolene." JAMA 242 (1979): 2772-4

14. Miller DH, Haas LF "Pneumonitis with dantrolene." J Neurol Neurosurg Psychiatry 47 (1984): 553-4

15. Felz MW, HavilandFoley DJ "Eosinophilic pleural effusion due to dantrolene: Resolution with steroid therapy." South Med J 94 (2001): 502-4

16. Pace-Balzan A, Ramsden RT "Sudden bilateral sensorineural hearing loss during treatment with dantrolene sodium (dantrium)." J Laryngol Otol 102 (1988): 57-8

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

Some side effects may not be reported. You may report them to the FDA.