Dantrolene

Dantrolene is thought to work in MH by interfering with the release of calcium from sarcoplasmic reticulum to the myoplasm.The average dose required to reverse the manifestations of MH is 2.5 mg/kg. If a relapse or recurrence occurs, dantrolene should be re-administered at the last effective dose.When used for the short-term treatment of MH there are usually no side-effects. Dantrolene has been used in the treatment of hyperthermia and rhabdomyolysis caused by theophylline overdose, consumption of ‘Ecstasy’ and ‘Eve’, and in the neuroleptic malignant syndrome and thyrotoxic storm. Neuroleptic malignant syndrome is characterised by hyperthermia, muscle rigidity, tachycardia, labile BP, sweating, autonomic dysfunction, urinary incontinence and fluctuating level of consciousness. It has been reported with haloperidol, fluphenazine, chlorpromazine, droperidol, thioridazine, metoclopramide, flupenthixol decanoate and tricyclic antidepressants.

Uses:
MH
Neuroleptic malignant syndrome (unlicensed)
Thyrotoxic storm (unlicensed)
Hyperthermia and rhabdomyolysis associated with theophylline overdose,
consumption of ‘Ecstasy’ and ‘Eve’ (unlicensed)

Contraindications:
Hepatic impairment (worsens)

Administration:
• IV: 1 mg/kg, repeated PRN up to 10 mg/kg
Reconstitute each 20 mg vial with 60 ml WFI and shake well
Each vial contains a mixture of 20 mg dantrolene sodium, 3 g mannitol and sodium hydroxide to yield a pH 9.5 when reconstituted with 60 ml WFI

Adverse effects:
Rash
Diarrhoea
Muscle weakness
Hepatotoxicity

Cautions:
Concurrent use of diltiazem (arrhythmias)
Concurrent use of calcium channel blockers (hypotension,myocardial
depression and hyperkalaemia reported with verapamil)