MAGNESIUM SULFATE

Class

Anticonvulsant / Antiarrhythmic

Pharmacology and Actions

1. Cardiac: stabilizes potassium pump, correcting repolarization. Shortens the QT interval in the presence of ventricular arrhythmias due to drug toxicity or electrolyte imbalance.
2. Obstetrics: controls seizures by blocking neuromuscular transmission. Also lowers blood pressure and decreases cerebral vasospasm.

Indications

1. Cardiac:
   1. Recommended for use in cardiac arrest only if torsades de pointes or suspected hypomagnesemia is present.
   2. Refractory VF (after lidocaine).
   3. Torsades de pointes with a pulse
2. Obstetrics: Pregnancy >20 weeks with signs and symptoms of pre-eclampsia, defined as:
   1. Blood pressure > 180 mm systolic or > 120 mm diastolic with altered mental status, or,
   2. Seizures

Precautions

1. AV block
2. Decrease in respiratory or cardiac function
3. Use with caution in patients taking digitalis

Administration

1. Torsades de pointes (not in cardiac arrest): Loading dose of 1 gram infused slowly over 60 minutes.
2. In pre-eclampsia/eclampsia patients, 2 grams diluted in 100 mL of normal saline over 5-20 minutes.  May repeat to a total dose of 6 grams.

Side Effects and Special Notes

1. Principle side effect is respiratory depression.  Ventilatory assistance may be needed.
2. Not for pediatric use.
3. Magnesium sulfate is very irritating when administered IV, thus dilution is always recommended.