Dantrolene

Chemical

A phenyl hydantoin derivative

Use

  1. Spasticity from UMN disorders
  2. Malignant Hyperthermia prophylaxis
  3. MH Crisis
  4. Reduce succinylcholine-induced muscle fasciculations and postoperative muscle pain

Presentation

25 or 100mg capsules of dantrolene sodium as a lyophilized orange powder containing 20mg dantrolene and 3g mannitol and NaOH

Dose

2.5mg/kg repeated up to 10mg/kg

Route

PO/IV

Onset

IV unknown

PO 15mins

DoA (duration)

PO unknown

IV 3hrs post infusion

MoA (mechanism)

Direct acting skeletal muscle relaxant

Binds to Ryanodine receptor on SR of skeletal muscle to inhibit calcium release, reducing skeletal muscle contraction

PD

CNS – marked GABA-ergic effects w sedation

GU – improves voiding

MSK – diminishes muscle twitches

PK

A

35% OBA

D

90% PPB to albumin

Vd 0.6L/kg

M

Liver by hydroxylation to active metabolites and by reductive pathways

E

Urinary metabolite excretion

Adverse Effects

CNS – muscle weakness, drowsiness, light-headed, confusion, seizures, fever

CVS – tachycardia

GI – hepatitis, anorexia, constipation, metallic taste, severe diarrhoea, GI bleeding

MSK – myalgia, back pain,

RESP – pleural effusion with pericarditis

Highly irritant with extravasation