What is the action of magnesium sulfate in this practice setting?

• A. Membrane stabilization, raises seizure threshold
• B. Causes vasodilation
• C. Increases heart rate
• D. Acts as a diuretic

Answer: (A)

Magnesium sulfate works primarily by stabilizing excitable membranes and raising the seizure threshold. It acts as a physiologic calcium antagonist, reducing calcium influx into neurons and at the neuromuscular junction, which lowers neurotransmitter release and dampens neuronal excitability. This makes seizures less likely or easier to control in settings like eclampsia or other seizure scenarios encountered in the field.

While magnesium can cause some vasodilation and may influence heart rate at high doses, those effects are not the main reason it’s used in this setting. It is not used as a diuretic. The key therapeutic action here is membrane stabilization that raises the seizure threshold.