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Generic Name: Dantrolene Capsules (DAN troe leen)
Brand Name: Dantrium
Easy-to-read patient leaflet for Dantrium (Dantrolene Capsules). Includes indications, proper use, special instructions, precautions, and possible side effects.
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Drug Information:
This is not a list of all drugs or health problems that interact with Dantrium (dantrolene capsules). Tell your doctor and pharmacist about all of your drugs (prescription or OTC, natural products, vitamins) and health problems. You must check to make sure that it is safe for you to take Dantrium (dantrolene capsules) with all of your drugs and health problems. Do not start, stop, or change the dose of any drug without checking with your doctor. Use Dantrium (dantrolene capsules) as ordered by your doctor. Read all information given to you. Follow all instructions closely. Learn more

Dantrium Side Effects

Dantrium Side Effects

Note: This document contains side effect information about dantrolene. Some of the dosage forms listed on this page may not apply to the brand name Dantrium.

For the Consumer

Applies to dantrolene: oral capsule

Other dosage forms:

  • intravenous powder for solution, intravenous powder for suspension


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 over 35 years old, 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.

Along with its needed effects, dantrolene (the active ingredient contained in Dantrium) 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


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


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

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


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.

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


Postmarketing reports: Anaphylaxis


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

Postmarketing reports: Thrombophlebitis and tissue necrosis


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

Nervous system

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

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


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


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

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


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

Frequency not reported: Myalgia, backache


Frequency not reported: Aplastic anemia, leukopenia, lymphocytic lymphoma, thrombocytopenia


Common (1% to 10%): Blurred vision

Frequency not reported: Visual disturbances, diplopia, excessive tearing


Common (1% to 10%): Feeling abnormal

Frequency not reported: Chills, fever, general malaise


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

Editorial References and Review

Medically reviewed by BestRx Medical Team Last updated on 1/1/2020.

Source: Drugs.com Dantrium