Magnesium Sulphate
Chemical
Magnesium Sulphate
Use
- Electrolyte replacement
- Tx Eclampsia & Pre-Eclampsia
- TdP
- Severe Asthma
- Box jellyfish envenomation
- Irukandji syndrome
Presentation
Ampoule, 10mmol/5ml
Dose
10-20mmol infused at a rate of 10mmol/20mins
Route
IV/IO
Onset
Immediate
DoA
30mins
MoA
- Co-factor of enzyme systems
- NMDA receptor antagonism – anticonvulsant
- Reduces Ach release at NMJ – reducing striated muscle contraction
- Inhibits Ca++ influx through dihdropyridine sensitive voltage-gated channels – relaxing smooth muscle
PD
PK
A
N/A
D
25-30%
M
None
E
Excreted by kidney, proportional to GFR
Adverse Effects
Hypotension
ECG changes
Diarrhoea
Urinary retention
CNS depression
Loss of deep tendon reflexes
Respiratory depression
Contradictions
Renal impairment, heart block, myasthenia gravis