Dantrolene acts peripherally at the motor end-plate within muscles therefore causing less potential for central nervous system side effects. However, its use is limited by hepatic side effects. Please note that the therapeutic effect may take weeks to develop.
Side Effects
1) Hepatitis (approx 2% risk) with potential for life threatening hepatotoxicity.
- Liver effects are reversible if identified early.
- Factors which increase the risk of hepatotoxicity include:
- Higher daily doses (exceeding 400 mg daily).
- Duration of therapy (most frequently reported between two and twelve months of treatment).
- Female gender.
- Age greater than 30 years.
- Prior history of liver disease/dysfunction.
- Receiving other hepatotoxic therapies concomitantly.
- Risk management:
- Advise patient about risks and early warning features of hepatotoxicity.
- Monitor liver function:
- 2 weekly for 6 weeks after start.
- 6 weekly for 6 months after start.
- If initiating any new liver enzyme inducing medication.
2) Other uncommon side effects are generally transient and occur early in treatment:
- Drowsiness, dizziness, weakness.
- General malaise or fatigue.
- Seizure.
- Diarrhoea.
Dose
- Start at 25mg daily.
- Increase in weekly increments of 25mg per day, dividing dose into 4 times daily increments as dose rises.
- Maximum dose is 100mg 4 times daily (usual maintenance is 75mg 3 times daily).