Skip to Content

Dantrolene Side Effects

In Summary

Commonly reported side effects of dantrolene include: drowsiness. See below for a comprehensive list of adverse effects.

For the Consumer

Applies to dantrolene: oral capsule

Other dosage forms:

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

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

Nervous system

Nervous system side effects have commonly included drowsiness (30%), dizziness (14%), and malaise. Speech disturbances, headache, seizures and hallucinations have been reported less frequently.[Ref]


Several reports of severe constipation and abdominal distention leading to functional obstruction have been reported.[Ref]

Gastrointestinal side effects have frequently included diarrhea which may be severe enough to require discontinuation. Constipation, abdominal cramps, nausea, and vomiting have been reported less frequently.[Ref]


Hematologic side effects have included aplastic anemia, leukopenia, and lymphocytic lymphoma.[Ref]


Musculoskeletal side effects have commonly included weakness which is usually tolerable. Myalgia and backache have also been reported.[Ref]


Risk of hepatic injury is greater in females, patients over 35 years of age, and in patients on concurrent medications. The severity of the reaction appears to increase with increases in dose and duration.[Ref]

Hepatic side effects have included hepatic injury (1.8%), hepatitis (0.6%), and fatal hepatitis (0.3%).[Ref]


Respiratory side effects have infrequently included pulmonary edema with the use of intravenous dantrolene. Pleural effusion and pneumonitis have also been reported.[Ref]


Cardiovascular side effects have infrequently included pericarditis (both with and without pleural effusion) in patients receiving oral dantrolene. Cardiovascular side effects reported postmarketing have included heart failure.[Ref]


Local side effects have included thrombophlebitis in patients receiving intravenous dantrolene.[Ref]


Dermatologic side effects have included rare reports of acne.[Ref]


Ocular side effects have included visual disturbances.[Ref]


Other side effects have included one case of bilateral hearing loss which was thought to have been secondary to dantrolene treatment.[Ref]


Hypersensitivity side effects reported postmarketing have included anaphylaxis.


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

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

3. "Product Information. Dantrium (dantrolene)." Procter and Gamble Pharmaceutic, Cincinnati, OH.

4. 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

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

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

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

8. Utili R, Boitnott JK, Zimmerman HJ "Dantrolene-associated hepatic injury. Incidence and character." Gastroenterology 72 (1977): 610-6

9. Wilkinson SP, Portmann B, Williams R "Hepatitis from dantrolene sodium." Gut 20 (1979): 33-6

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

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

12. 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

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

14. 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.