TRADE NAME: Magnesium
CLASS: Electrolyte, Anticonvulsant, Antidysrhythmic
DESCRIPTION: Electrolyte, cation, Physiologic calcium channel blocker, CNS depressant and anticonvulsant. Acts as neuromuscular blocker.
ACTIONS: Raising magnesium level inhibits calcium flux across cell membranes, corrects hypomagnesemia, depresses CNS and inhibits muscle cell activity.
INDICATIONS: Convulsive states associated with severe preeclampsia and eclampsia, Torsades de Pointes, refractory/recurrent VF or pulseless VT, refractory bronchospasm
Onset: Immediate in IV , IM: 1 hour
Peak Effect: Varies
Duration: 1 hour
CONTRAINDICATIONS: Contraindicated in: High degree heart block, shock, patients on digitalis or who are on dialysis or who are hypocalcemic, or persistent hypertension. Use with caution in patients with other CNS depressants on board.
Patients with impaired renal function may not be able to eliminate excess Mg++
Use with caution in patients with asthma.
CNS: Sedation, confusion, muscle weakness, paralysis
CV: Hypotension, bradycardia, heart block
Resp: Depression, arrest
Other: Flushing, sweating, hypotension, hypocalcemia
INTERACTIONS: Incompatible with many drugs. Those present in the prehospital arena include:
digitalis, alcohol, salicylates, and sodium bicarbonate.
ADULT: VF/VT/Torsade: 1 - 2 grams. Maintenance infusion is indicated following initial IV dose at a rate of 0.5 - 1.0 g/hr. IV for control of Torsade.
PEDIATRIC: VFVT/Torsade: 25 - 50 mg/kg IV/IM
Eclampsia: 1 - 4 grams of 10% solution. Smallest effective dose should be used. Dose rate should not exceed 1.5 ml (150mg)/min.
Bronchospasm: Adults 1 - 2 grams, Pediatric: 25 - 50 mg/kg
ROUTES: IV over 1-20 minutes depending upon illness and seriousness.
It is preferred to use a more dilute solution (10%) when administering IV.
NOTES: Calcium is antidote if respiratory depression occurs. Continuous cardiac monitoring is essential. General signs of toxicity include: sedation, thirst, diarrhea, muscle weakness.