Dantrolene Oral Side Effects 

Side Effects of Dantrolene - for the Consumer 

Dantrolene 

All medicines may cause  side effects, but many people have no, or minor, side effects. Check with your doctor if any of these most COMMON side  effects persist or become bothersome when using Dantrolene: 

Decreased grip strength; diarrhea; dizziness; drowsiness; general body discomfort; lightheadedness; muscle weakness; nausea; pain or redness at injection site; unusual tiredness; weakness. 

Seek medical attention right away if any of these SEVERE side effects occur when using Dantrolene: 

Severe allergic reactions (rash; hives; itching; difficulty breathing; tightness in the chest; swelling of the mouth, face, lips, or tongue); blood vessel inflammation; chest pain; dark urine; difficulty swallowing; inflammation at the injection site; severe stomach or abdominal pain; shallow breathing; unusual tiredness; yellowing of skin or eyes. 

Dantrolene Capsules 

All medicines  may cause side effects, but many people have no, or minor, side  effects. Check with  your doctor if any of these most COMMON side effects persist or become bothersome when using Dantrolene Capsules: 

Diarrhea; dizziness; drowsiness; general body discomfort; nausea; sensitivity to sunlight; unusual tiredness; vision changes; weakness. 

Seek medical attention right away if any of these SEVERE side effects occur when using Dantrolene Capsules: 

Severe allergic reactions (rash; hives; difficulty breathing; tightness in the chest; swelling of the mouth, face, lips, or tongue); blood in the urine; bloody or black, tarry stools; chest pain; coffee ground-like vomit; confusion; dark urine; depression; difficulty urinating; fast heartbeat; fever or chills; seizures;  severe or persistent diarrhea; severe stomach or abdominal pain; shortness of breath; unusual tiredness; vomiting; yellowing of the skin or eyes. 

Dantrolene Side Effects - for the Professional 

Dantrolene 

The most frequently occurring side effects of Dantrolene sodium have been drowsiness, dizziness, weakness, general malaise, fatigue, and diarrhea. These are generally transient, occurring early in treatment, and can often be obviated by beginning with a low dose and increasing dosage gradually until an optimal regimen is established. Diarrhea may be severe and may necessitate temporary withdrawal of Dantrolene sodium therapy. If diarrhea recurs upon readministration of Dantrolene sodium, therapy should probably be withdrawn permanently. 

Other less frequent side effects, listed according to system, are: 

Gastrointestinal: Constipation, GI bleeding, anorexia, swallowing difficulty, gastric irritation, abdominal cramps. 

Hepatobiliary: Hepatitis. 

Neurologic: Speech disturbance, seizure, headache, light-headedness, visual disturbance, diplopia, alteration of taste, insomnia. 

Cardiovascular: Tachycardia, erratic blood pressure, phlebitis. 

Psychiatric: Mental depression, mental confusion, increased nervousness. 

Urogenital: Increased urinary frequency, crystalluria, hematuria, difficult erection, urinary incontinence and/or nocturia, difficult urination and/or urinary retention. 

Integumentary: Abnormal hair growth, acne-like rash, pruritus, urticaria, eczematoid eruption, sweating. 

Musculoskeletal: Myalgia, backache. 

Respiratory: Feeling of suffocation. 

Special Senses:  Excessive tearing. 

Hypersensitivity:  Pleural effusion with pericarditis. 

Other: Chills and fever. 

Side Effects by Body System 

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. 

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

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. 

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

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

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

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. 

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

Cardiovascular 
Cardiovascular side effects have infrequently included pericarditis (both with and without pleural effusion) in patients receiving oral dantrolene. 

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

Dermatologic 
Dermatologic side effects have included rare reports of acne. 

Ocular 
Ocular side effects have included visual disturbances. 

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