Summary

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:

• intravenous powder for solution, intravenous powder for suspension

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.

General

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]

Hepatic

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

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

Gastrointestinal

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]

Hypersensitivity

Postmarketing reports: Anaphylaxis

Local

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

Postmarketing reports: Thrombophlebitis and tissue necrosis^[Ref]

Dermatologic

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]

Psychiatric

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

Genitourinary

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

Cardiovascular

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]

Respiratory

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]

Musculoskeletal

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

Frequency not reported: Myalgia, backache^[Ref]

Hematologic

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

Ocular

Common (1% to 10%): Blurred vision

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

Other

Common (1% to 10%): Feeling abnormal

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

Renal

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