Magnesium Sulfate

Question 1

Class

Answer 1

Electrolyte

Anticonvulsant

Question 2

Description

Answer 2

Reduces striated muscle contractions & block’s peripheral neuromuscular transmission by reducing acetylcholine release @ the myoneural junction

Toxemia of pregnancy (eclampsia) seizures

Uterine relaxation (inhibit premature labor contractions)

Bronchodilator after beta agonist & anticholinergic agents have been used

Magnesium deficiency

Torsades de pointes or hypomagnesemia cardiac arrest

Question 3

Onset & Duration

Answer 3

Onset:
IV: immediate IM: 3-4 hours

Duration:
IV: 30 minutes IM: 3-4 hours

Question 4

Indications

Answer 4

Eclampsia seizures

Torsades de pointes or hypomagnesemia cardiac arrest

Deadly V dysrhythmias (digitalis toxicity)

Hypomagnesemia

Status asthmaticus not responsive to beta adrenergic drugs

Question 5

Contraindications

Answer 5

Heart block or myocardial damage

Hypermagnesemia or hypercalcemia

Diabetic coma

Question 6

Adverse Reactions

Answer 6

Diaphoresis
Facial flushing
Depressed reflexes
Hypothermia
Bradycardia
Circulatory collapse
Respiratory depression/arrest
Diarrhea
Nausea/Vomiting

Question 7

Drug Interactions

Answer 7

CNS depressant effects may be enhanced if the pt is taking other CNS depressants

Serious changes in cardiac function may occur w/ cardiac glycosides (avoid excess magnesium administration)

Question 8

How supplied

Answer 8

10%, 12.5%, 50% solutions in 40, 80, 100, & 125 mg/ml

Question 9

Dosage & Administration (Adult)

Answer 9

Eclamptic seizures:
4 g diluted in D5W or NS for IV piggyback load over 15-20 minutes, followed by continuous infusion of 1-2 g/h; max dose of 30-40 g/d

Pulseless Arrest (hypomagnesemia or Torsades de pointes) or Status Asthmaticus:
1-2 g (2-4 mL of a 50% solution) diluted in 10 mL of D5W IV/IO push

Torsades de pointes w/ Pulse or Acute MI w/ Hypomagnesemia:
Loading dose 1-2 g in 50-100 mL of D5W over 5-60 minutes IV; followed w/ 0.5-1 g/h IV (titrate dose to control Torsades de pointes)

Question 10

Dosage & Administration (Peds)

Answer 10

Pulseless Arrest (hypomagnesemia or Torsades de pointes) or Status Asthmaticus:
25-50 mg/kg IV/IO (max 2 g) over 10-20 minutes; over 15-30 minutes for Status Asthmaticus

Torsades de pointes w/ Pulse or Acute MI w/ Hypomagnesemia:
same as Pulseless arrest

Question 11

Special considerations

Answer 11

Pregnancy Safety: Category A

For tx of eclampsia.

Recommend not to be given 2 hours before delivery if possible.

IV calcium gluconate/chloride should be available as an antagonist if needed.

Convulsions may occur up to 48 hours after delivery, necessitating continued therapy.

Having the baby is the cure for eclampsia.

Caution must be exercised in pts w/ renal failure because it’s cleared by the kidneys & can reach toxic levels easily