Dantrolene

Ryanodine Antagonist·Musculoskeletal & Rheumatology

Malignant Hyperthermia (triggered by volatile anaesthetics/suxamethonium), chronic severe spasticity

ANTIDOTEDantrium25 mgS4TGA

Max Dose

10 mg/kg (IV Load)

Half-life

4-8 h

Hepatotoxicity

CRITICAL

Muscle Weakness

PROFOUND

Rapid Summary

Overview

Direct-acting skeletal muscle relaxant. The absolute life-saving, definitive antidote for Malignant Hyperthermia (MH) and Neuroleptic Malignant Syndrome (NMS).

Maximum Dose

Max 10 mg/kg (IV for MH crisis). Oral max is 400 mg/day.

Clinical Focus

Directly paralyzes skeletal muscle. Causes profound, dose-dependent hepatotoxicity if used orally for chronic spasticity.

Bottom Line

Dantrolene is the only specific treatment for malignant hyperthermia and NMS, but causes hepatotoxicity requiring liver function monitoring and significant muscle weakness.

Formulation & Access

Brand Names

Dantrium

Oral Routes

Capsules (25 mg, 50 mg).

Parenteral

Vials (20 mg powder). Extremely difficult to dissolve. Requires massive volumes of sterile water (60 mL per vial) and intense shaking by multiple staff during a crisis.

Prescribing & PBS

Hospital OT/ICU emergency supply.

Indications & Use

Primary

TGA

Malignant Hyperthermia (triggered by volatile anaesthetics/suxamethonium), chronic severe spasticity.

Off-Label

OFF

Neuroleptic Malignant Syndrome, severe MDMA/Amphetamine-induced hyperthermia/rigidity.

Clinical Place

Emergency rescue drug stored in every operating theatre 'MH Cart'.

Quick reference

Class & Role

Ryanodine Antagonist — Direct-acting skeletal muscle relaxant.

Route / Formulation

Capsules (25 mg, 50 mg). (Dantrium)

Usual Dose & Max

IV 2.5 mg/kg STAT rapid push. Repeat 1 mg/kg every 5 mins until symptoms (rigidity/hypercarbia/fever) stop. Max 10 mg/kg.

Key Indication Doses

Malignant Hyperthermia (Crisis): IV 2.5 mg/kg STAT rapid push. Repeat 1 mg/kg every 5 mins until symptoms (rigidity/hypercarbia/fever) stop. Max 10 mg/kg. Neuroleptic Malignant Syndrome: IV 1-2.5 mg/kg, or PO 50-200 mg/day in divided doses (Off-label, but standard of care). Chronic Spasticity (Oral): Start PO 25 mg OD. Titrate up weekly. Max 400 mg/day (rarely used due to liver toxicity).

Best Uses

Dantrolene is the only specific treatment for malignant hyperthermia and NMS, but causes hepatotoxicity requiring liver function monitoring and significant muscle weakness.

Avoid / Cautions

Active liver disease (for chronic oral use). NONE for IV emergency use. Pregnancy Category C.

Key Risks

Hepatic: Fatal symptomatic hepatitis (especially in females > 35 years taking oral doses > 300 mg/day for chronic spasticity). Neuromuscular: Profound, generalized muscle weakness (can impair respiratory muscles and swallowing). Gastrointestinal: Severe diarrhea, nausea.

Key Interactions

Calcium Channel Blockers (Verapamil, Diltiazem). Co-administration of IV Dantrolene with CCBs causes catastrophic cardiovascular collapse and hyperkalemia. NEVER mix.

Monitoring

For chronic oral use, baseline and frequent (monthly) LFTs. Stop immediately if transaminases rise. Check U&E (K+) and ABGs during acute crisis. Continuous ICU-level monitoring (Core temp, ETCO2, HR, BP) during MH crisis.

Clinical Pearl

Dantrolene powder is highly lipophilic and notoriously stubborn to dissolve in water. In an MH crisis, you need ~10 vials for an average adult. It takes multiple nurses furiously shaking 60mL syringes for minutes to prepare it. Newer formulations (Ryanodex) dissolve in 5mL instantly but are highly expensive.

Access

Dantrium25 mg

Brand: Dantrium
Formulation: Capsules (25 mg, 50 mg)

Dantrolene

Ryanodine Antagonist·Musculoskeletal & Rheumatology

Malignant Hyperthermia (triggered by volatile anaesthetics/suxamethonium), chronic severe spasticity

ANTIDOTEDantrium25 mgS4TGA

Max Dose

10 mg/kg (IV Load)

Half-life

4-8 h

Hepatotoxicity

CRITICAL

Muscle Weakness

PROFOUND

Rapid Summary

Overview

Direct-acting skeletal muscle relaxant. The absolute life-saving, definitive antidote for Malignant Hyperthermia (MH) and Neuroleptic Malignant Syndrome (NMS).

Maximum Dose

Max 10 mg/kg (IV for MH crisis). Oral max is 400 mg/day.

Clinical Focus

Directly paralyzes skeletal muscle. Causes profound, dose-dependent hepatotoxicity if used orally for chronic spasticity.

Bottom Line

Dantrolene is the only specific treatment for malignant hyperthermia and NMS, but causes hepatotoxicity requiring liver function monitoring and significant muscle weakness.

Formulation & Access

Brand Names

Dantrium

Oral Routes

Capsules (25 mg, 50 mg).

Parenteral

Vials (20 mg powder). Extremely difficult to dissolve. Requires massive volumes of sterile water (60 mL per vial) and intense shaking by multiple staff during a crisis.

Prescribing & PBS

Hospital OT/ICU emergency supply.

Indications & Use

Primary

TGA

Malignant Hyperthermia (triggered by volatile anaesthetics/suxamethonium), chronic severe spasticity.

Off-Label

OFF

Neuroleptic Malignant Syndrome, severe MDMA/Amphetamine-induced hyperthermia/rigidity.

Clinical Place

Emergency rescue drug stored in every operating theatre 'MH Cart'.

Quick reference

Class & Role

Ryanodine Antagonist — Direct-acting skeletal muscle relaxant.

Route / Formulation

Capsules (25 mg, 50 mg). (Dantrium)

Usual Dose & Max

IV 2.5 mg/kg STAT rapid push. Repeat 1 mg/kg every 5 mins until symptoms (rigidity/hypercarbia/fever) stop. Max 10 mg/kg.

Key Indication Doses

Best Uses

Dantrolene is the only specific treatment for malignant hyperthermia and NMS, but causes hepatotoxicity requiring liver function monitoring and significant muscle weakness.

Avoid / Cautions

Active liver disease (for chronic oral use). NONE for IV emergency use. Pregnancy Category C.

Key Risks

Key Interactions

Calcium Channel Blockers (Verapamil, Diltiazem). Co-administration of IV Dantrolene with CCBs causes catastrophic cardiovascular collapse and hyperkalemia. NEVER mix.

Monitoring

Clinical Pearl

Access

Dantrium25 mg

Brand: Dantrium
Formulation: Capsules (25 mg, 50 mg)