👤 By the CinnaRN Clinical Content Team🕐 Updated 2026-08-23🏷️ Pharmacological Therapies🔖 Free to read, print, and share
Also known as: mag · mag sulfate · magnesium drip · seizure prevention drug in pregnancy
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Use this quick-reference guide to spot, treat, and prevent Magnesium Sulfate Therapy on the NCLEX. Keep it handy during review and on exam day!
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📒 The 1-minute cheat sheet
📌 Use
Seizure prevention (preeclampsia)
Tocolytic for preterm labor
🧪 Monitor
Therapeutic level 4-7 mEq/L
DTRs, RR, urine output, LOC
📌 Toxicity
Absent DTRs = early toxicity
RR < 12, urine < 30 mL/hr → HOLD
↓ LOC, resp/cardiac arrest
✅ Antidote
Calcium gluconate at bedside
📚 Magnesium Sulfate Therapy — 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 a central nervous system depressant used in obstetrics primarily to prevent and control seizures in preeclampsia and eclampsia, and secondarily as a tocolytic to slow preterm labor and for fetal neuroprotection. It works by relaxing smooth muscle and depressing neuromuscular transmission. Because it has a narrow therapeutic range, the nurse must continuously monitor for toxicity. Antidote memory aid: Calcium gluconate reverses magnesium toxicity.
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Key points
Understand these first
It depresses the central nervous system and relaxes smooth muscle, reducing seizure activity and uterine contractions.
The therapeutic serum range for seizure prophylaxis is about 4-7 mEq/L; normal serum magnesium is 1.3-2.1 mEq/L.
Early toxicity appears as loss of deep tendon reflexes, the first warning sign.
Progressive toxicity causes respiratory depression, decreased urine output, hypotension, and eventually cardiac arrest.
Because it is renally excreted, low urine output rapidly raises serum levels and toxicity risk.
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Nursing priorities
What to do, in order
Assess deep tendon reflexes, respiratory rate, blood pressure, and level of consciousness hourly during infusion.
Monitor urine output and keep it at 30 mL/hr or more, since the drug is excreted by the kidneys.
Use an infusion pump and frequently verify the rate to prevent accidental overdose.
Keep calcium gluconate readily available at the bedside as the antidote for magnesium toxicity.
Monitor the fetal heart rate and newborn for respiratory depression and decreased muscle tone after birth.
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Red flags — report now
Escalate immediately
Stop the infusion and notify the provider for absent deep tendon reflexes, respirations under 12, or urine output under 30 mL/hr.
Administer calcium gluconate immediately for signs of serious magnesium toxicity.
Report a serum magnesium level above the therapeutic range or signs of cardiac changes.
Watch the newborn for hypotonia and respiratory depression if the mother received magnesium near delivery.
Loss of deep tendon reflexes around 8-10 mEq/L; respiratory depression around 10-13 mEq/L
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Patient teaching
What patients must know
Expect to feel warm, flushed, or sleepy during the infusion; report difficulty breathing or feeling unable to move.
Tell the nurse if you feel weak, very drowsy, or have trouble urinating.
Frequent assessments are normal and necessary to keep you safe on this medication.
❓ Magnesium Sulfate Therapy: NCLEX FAQs
What are the priority nursing interventions for Magnesium Sulfate Therapy?
Assess deep tendon reflexes, respiratory rate, blood pressure, and level of consciousness hourly during infusion. Monitor urine output and keep it at 30 mL/hr or more, since the drug is excreted by the kidneys. Use an infusion pump and frequently verify the rate to prevent accidental overdose. Keep calcium gluconate readily available at the bedside as the antidote for magnesium toxicity.
What are the warning signs of Magnesium Sulfate Therapy a nurse must report?
Stop the infusion and notify the provider for absent deep tendon reflexes, respirations under 12, or urine output under 30 mL/hr. Administer calcium gluconate immediately for signs of serious magnesium toxicity. Report a serum magnesium level above the therapeutic range or signs of cardiac changes. Watch the newborn for hypotonia and respiratory depression if the mother received magnesium near delivery.
What do I need to know about Magnesium Sulfate Therapy for the NCLEX?
It depresses the central nervous system and relaxes smooth muscle, reducing seizure activity and uterine contractions. The therapeutic serum range for seizure prophylaxis is about 4-7 mEq/L; normal serum magnesium is 1.3-2.1 mEq/L. Early toxicity appears as loss of deep tendon reflexes, the first warning sign. Progressive toxicity causes respiratory depression, decreased urine output, hypotension, and eventually cardiac arrest.
What patient teaching is important for Magnesium Sulfate Therapy?
Expect to feel warm, flushed, or sleepy during the infusion; report difficulty breathing or feeling unable to move. Tell the nurse if you feel weak, very drowsy, or have trouble urinating. Frequent assessments are normal and necessary to keep you safe on this medication.
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Quick Tip
It depresses the central nervous system and relaxes smooth muscle, reducing seizure activity and uterine contractions.