👤 By the CinnaRN Clinical Content Team🕐 Updated 2026-08-23🏷️ Pharmacological Therapies🔖 Free to read, print, and share
Also known as: mag · MgSO4 · Epsom salt (oral)
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Use this quick-reference guide to spot, treat, and prevent Magnesium Sulfate on the NCLEX. Keep it handy during review and on exam day!
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📒 The 1-minute cheat sheet
📌 Use
Preeclampsia → prevent seizures
Preterm labor → tocolytic
📌 Toxic
Loss of DTRs = first sign
RR <12, ↓BP, ↓LOC
Resp/cardiac arrest if severe
🧪 Monitor
Mg level 4-7 mEq/L therapeutic
DTRs, RR, BP, urine output q hr
✅ Do
Antidote: calcium gluconate ready
Hold + report absent reflexes
📚 Magnesium Sulfate — full study notes
The cheat sheet above is your quick recall card. These notes go deeper — what it is, what to do first, what must be reported, and what to teach.
Magnesium sulfate is used to prevent and treat seizures in preeclampsia and eclampsia and as a tocolytic for preterm labor; IV mag also treats severe hypomagnesemia and certain arrhythmias. It depresses the CNS and smooth muscle. Key principle: monitor for magnesium toxicity, and keep calcium gluconate at the bedside as the antidote.
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Key points
Understand these first
In obstetrics it prevents seizures in preeclampsia and relaxes the uterus in preterm labor.
Calcium gluconate is the antidote for magnesium toxicity.
The first signs of toxicity are loss of deep tendon reflexes, then respiratory depression, then cardiac arrest.
Therapeutic level for preeclampsia is about 4-7 mEq/L; higher levels cause toxicity.
It also causes flushing, warmth, decreased urine output, and lowered blood pressure.
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Nursing priorities
What to do, in order
Assess deep tendon reflexes; absent reflexes signal early toxicity, so hold and notify the provider.
Monitor respiratory rate (keep above 12), blood pressure, and urine output (at least 30 mL/hour).
Keep calcium gluconate available at the bedside as the antidote.
Use an infusion pump and monitor serum magnesium levels.
For preeclampsia, monitor maternal vitals and fetal heart rate.
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Red flags — report now
Escalate immediately
Hold infusion and report absent deep tendon reflexes, respirations below 12, or urine below 30 mL/hour (toxicity).
Have calcium gluconate ready for severe toxicity.
Report sudden hypotension or decreased level of consciousness.
Expect a feeling of warmth or flushing during the infusion.
Report difficulty breathing, muscle weakness, or feeling very drowsy.
Frequent monitoring of reflexes, breathing, and the baby is expected.
❓ Magnesium Sulfate: NCLEX FAQs
What are the priority nursing interventions for Magnesium Sulfate?
Assess deep tendon reflexes; absent reflexes signal early toxicity, so hold and notify the provider. Monitor respiratory rate (keep above 12), blood pressure, and urine output (at least 30 mL/hour). Keep calcium gluconate available at the bedside as the antidote. Use an infusion pump and monitor serum magnesium levels.
What are the warning signs of Magnesium Sulfate a nurse must report?
Hold infusion and report absent deep tendon reflexes, respirations below 12, or urine below 30 mL/hour (toxicity). Have calcium gluconate ready for severe toxicity. Report sudden hypotension or decreased level of consciousness.
What do I need to know about Magnesium Sulfate for the NCLEX?
In obstetrics it prevents seizures in preeclampsia and relaxes the uterus in preterm labor. Calcium gluconate is the antidote for magnesium toxicity. The first signs of toxicity are loss of deep tendon reflexes, then respiratory depression, then cardiac arrest. Therapeutic level for preeclampsia is about 4-7 mEq/L; higher levels cause toxicity.
What patient teaching is important for Magnesium Sulfate?
Expect a feeling of warmth or flushing during the infusion. Report difficulty breathing, muscle weakness, or feeling very drowsy. Frequent monitoring of reflexes, breathing, and the baby is expected.
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Quick Tip
In obstetrics it prevents seizures in preeclampsia and relaxes the uterus in preterm labor.