Magnesium Sulfate (MgSO4)

Question 1

Class (3)

Answer 1

• Electrolyte
• CNS depressant
• Anticonvulsant

Question 2

Actions (3)

Answer 2

• For tx or prophylaxis of SZ due to toxemia of pregnancy by decreasing neuronal excitability (anticonvulsant)
• Reduces the incidence of postinfarction ventricular arrhythmias by increasing membrane stability and decreasing ventricular excitability
• May result in relaxation of bronchial and vascular smooth muscle which is probably secondary due to calcium blockade

Question 3

Indications (7)

Answer 3

• Refractory VF/VT
• Torsades
• Refractory SZ related to hypomagnesemia especially in alcoholics
• Eclampsia
• Hyper-reflexia of toxemia of pregnancy (pre-eclampsia)
• Cardiac arrhythmias due to dig toxicity
• Controversial: refractory bronchospasm not responsive to beta agonist, steroids, aminophylline

Question 4

Dosage/Route

Answer 4

• For acute administration during VT, 1 or 2 g of Mag in 10 cc over 1-2 min
• In VF should be given IV push follow up infusion of 0.5-1 g/hr for 24 hr
• Torsades=2 g IV bolus, followed by 2nd 2 g bolus if no response, followed by infusion
• Anticonvulsant=1-4 g IV over 30 minutes or more rapidly if seizing (over 5 min)

Question 5

Standard Prep

Answer 5

1 g/2 mL, 5 g/10 mL

Question 6

Contraindications (2)

Answer 6

• Heart block

- Controversy in acute MI pt

Question 7

Side Effects (1:4, 2:5)

Answer 7

• From too rapid IV administration: flushing, hypotension, sweating, mild bradycardia
• Hypermagnesemia: may produce depressed reflexes (patella), flaccid paralysis, circulatory collapse, respiratory depression or paralysis, and diarrhea

Question 8

Precautions (5)

Answer 8

• Monitor RR because respiratory depression is a serious side effect of hypermagnesemia
• IV Calcium Chloride should be available as an antagonist
• Concurrent use with CNS depressant requires lower dosage adjustments
• Monitor EKG
• Use with caution in renal failure patients