Indications
Dantrolene Sodium is a muscle relaxant. Taken by mouth, it is used to reduce severe muscle stiffness and spasm (spasticity) caused by conditions such as spinal cord injury, stroke, multiple sclerosis and cerebral palsy. Given by injection in hospital, it is the emergency treatment for malignant hyperthermia, a rare, life threatening reaction to some anaesthetic drugs.
How It Works
Muscles contract when calcium is released inside the muscle fibres. Dantrolene acts directly on the muscle, reducing the release of calcium from its internal stores. This weakens the force of contraction, easing stiffness and spasm. It works on the muscle itself rather than on the brain or nerves.
Dosage and Administration
For spasticity, treatment starts with a low dose, often 25 mg once a day, and is increased slowly over several weeks to the lowest dose that gives benefit, as prescribed by your doctor. The maximum oral dose is usually 400 mg a day. If there is no improvement after about 6 weeks, the doctor will usually stop it. The injection for malignant hyperthermia is given only by a doctor in hospital.
Interactions
- Alcohol, sleeping tablets, benzodiazepines and other sedatives increase drowsiness.
- Oestrogen containing medicines may increase the risk of liver damage.
- Calcium channel blockers such as Verapamil given by injection with Dantrolene injection can cause dangerous heart problems.
- Other medicines that can harm the liver add to the risk.
Contraindications
- Active liver disease (oral use).
- Spasticity that helps a person stand, balance or move, where loosening the muscles would make function worse.
- Allergy to Dantrolene.
Side Effects
Common side effects include drowsiness, dizziness, muscle weakness, tiredness, diarrhoea (which can be severe), nausea, loss of appetite and headache. The most serious risk with long term oral use is liver damage, which is more likely at higher doses, in women and in people over 35.
Get urgent medical help if you notice yellowing of the skin or eyes, dark urine, pale stools, severe stomach pain, severe or bloody diarrhoea, chest pain or breathlessness, or signs of a serious allergic reaction.
Pregnancy and Lactation
Oral Dantrolene should not be used during pregnancy unless a doctor decides it is clearly needed. In malignant hyperthermia, the injection may be life saving and is given when needed. It passes into breast milk, so breastfeeding is not recommended during oral treatment.
Precautions and Warnings
- Liver blood tests should be done before starting and regularly during treatment.
- Do not drive or use machines if you feel drowsy or weak.
- Take care if you have heart or lung disease.
- Avoid too much sun, as it may make the skin sensitive.
Overdose
Overdose may cause severe weakness, drowsiness, confusion, vomiting, diarrhoea and breathing problems. Seek emergency medical help straight away. Treatment is supportive in hospital.
Therapeutic Class
Direct acting skeletal muscle relaxant.
Storage
Store below 30°C in a dry place, away from light and out of the reach of children.
Prepared by the Oshud Alo team from standard drug references. For information only; always follow your doctor's advice.