Magnesium sulfate

Mechanism of Action: Depresses CNS, blocks peripheral neuromuscular transmission, produces anticonvulsant effects; decreases amount of acetylcholine released at end-plate by motor nerve impulse.

Slows rate of SA node impulse formation in myocardium and prolongs conduction time. Promotes movement of calcium, potassium, and sodium in and out of cells and stabilizes excitable membranes. Promotes osmotic retention of fluid in colon, causing distention and increased peristaltic activity, which subsequently results in bowel evacuation

Classification; electrolyte, anticonvulsant, saline laxative, antacid


  • Hypomagnesaemia
  • Arrhythmias
  • Severe acute asthma
  • Seizures

Contraindications: abdominal pain, nausea/vomiting, acute surgical abdomen, rectal bleeding, heart block, myocardial damage

Side effects: flaccid paralysis, circulatory collapse, hypotension, heart block, nausea, vomiting, anorexia, cramps, fluid imbalances, respiratory depression/paralysis

Controlled: High-Alert