QAS Magnesium Sulphate DTP

Vocabulary practice flashcards covering the pharmacological actions, indications, dosing presentation, pharmacokinetics, contraindications, and side effects of magnesium from the Queensland Ambulance Service clinical guidelines.

Drug class

Electrolyte.

Pharmacology

Acts as an important cofactor in multiple processes, producing vasodilation and bronchodilation through inhibition of smooth muscle contraction; also possesses anticonvulsant and anti-dysrrhythmic properties.

Metabolism

Filtered in the kidneys and excreted predominantly in urine, with small amounts eliminated in faeces and saliva.

Indications

1. Box jellyfish (Chironex fleckeri) envenomation (unresponsive to antivenom therapy)

2. Eclampsia

3. Irukandji syndrome (with intractable pain unrelieved by narcotic analgesia AND/OR systolic BP $> 160\,\text{mmHg}$)

4. Torsades de Pointes

5. Severe life-threatening asthma (only in patients who have required IM/IV adrenaline)

Contraindications

1. Allergy AND/OR Adverse Drug Reaction

2. Atrioventricular (AV) block

3. Renal failure.

Precautions

Renal impairment.

Side effects

1. Pain at the cannulation site

2. Magnesium toxicity (manifesting as hypotension/respiratory depression and loss of deep tendon reflexes).

Presentation

Ampoule, containing 10mmol (2.5g)/5ml, of magnesium sulphate heptahydrate.

Pharmacokinetics

Onset: Immediate.

Duration: 30 minutes

Half-life: Variable

Half-life

Variable.

Adult doses:

1. Irukandji

2. Box Jellyfish

3. Severe life threatening asthma

IV & IO: 10mmol over 20 minutes. Repeated once at 20 minutes, total max dose 20mmol.

Mix 10mmol (5ml) of magnesium sulphate with 15ml of sodium chloride in a 30ml springfusor syringe to achieve 10mmol/20ml. Administer at a rate of 60ml/hour (over 20 minutes)

Adult doses: Eclampsia

IV & IO: 20mmol over 20 minutes.

Mix 20mmol (10ml) of magnesium sulphate with 10ml of sodium chloride in a 30ml springfusor syringe to achieve 20mmol/20ml. Administer at a rate of 60ml/hour (over 20 minutes).

Adult doses: Torsades de Pointes

IV & IO: 10mmol over 10 minutes. Repeated once at 10 minutes, total max dose 20mmol.

Mix 10mmol (5ml) of magnesium sulphate with 5ml of sodium chloride in a 30ml springfusor syringe to achieve a concentration of 10mmol/10ml. Administer at a rate of 60ml/hour (over 10 mins).

Paediatric doses:

1. Irukandji

2. Box jellyfish

IV: 0.1mmol/kg over 15 minutes (rounded to the nearest 0.5mmol). Single dose does not exceed 5mmol. Repeated once at 15 minutes. Total max dose 10mmol.

Mix 0.1mmol/kg of magnesium sulphate with sodium chloride in a 30ml springfusor syringe to achieve a concentration of 0.1mmol/kg in 15ml. Administer at a rate of 60ml/hour (over 15 minutes)

IO: Contact the consult line for approval.

Paediatric dose: Torsades de Pointes

IV & IO: 0.1mmol/kg over 10 minutes (rounded to the nearest 0.5mmol). Single dose does not exceed 5mmol. Repeated once at 10 minutes. Total max dose 10mmol.

Mix 0.1mmol/kg of magnesium sulphate with sodium chloride in a 30ml springfusor syringe to achieve a concentration of 0.1mmol/kg in 10ml. Administer at a rate of 60ml/hour (over 10 minutes)

Paediatric dose: severe life threatening asthma

IV & IO: 0.1mmol/kg over 10 minutes (rounded to the nearest 0.5mmol). Single dose does not exceed 5mmol.

Mix 0.1mmol/kg of magnesium sulphate with sodium chloride in a 30ml springfusor syringe to achieve a concentration of 0.1mmol/kg in 10ml. Administer at a rate of 60ml/hour (over 10 minutes)