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Calculates the total 24-hour magnesium sulfate dose for seizure prophylaxis in preeclampsia with severe features or eclampsia using standard intravenous regimens (ACOG 2020): a 4–6 g IV loading dose over 20–30 minutes followed by a 1–2 g/hour maintenance infusion.
Total 24-h dose (g) = Loading dose (4–6 g IV) + Maintenance (1–2 g/h) × 24 h
Therapeutic serum magnesium target is 4.8–8.4 mg/dL (2–3.5 mEq/L); toxicity: loss of patellar reflexes ~ 10 mg/dL, respiratory depression ~ 12 mg/dL, cardiac arrest ~ 15–17 mg/dL.
Magnesium sulfate is the drug of choice for seizure prophylaxis in preeclampsia with severe features and for eclampsia. ACOG (PB 222, 2020) recommends an initial IV loading dose of 4–6 g over 20–30 minutes, followed by a maintenance infusion of 1–2 g/h (typically 2 g/h) for 24 hours. The Zuspan regimen (4 g IV + 2 g/h) and Pritchard regimen (4 g IV + 10 g IM, then 5 g IM every 4 h) are classic alternatives. This calculator sums the total 24-hour dose for the selected IV load and maintenance rate.
Specialty
ObstetricsCategory
Obstetrics & GynecologyDifficulty
Basic
Estimated Time
30 seconds
Version
1.0
Last Updated
2026-08-16
Formula
Keywords
Normal Range
Therapeutic serum magnesium target is 4.8–8.4 mg/dL (2–3.5 mEq/L); toxicity: loss of patellar reflexes ~ 10 mg/dL, respiratory depression ~ 12 mg/dL, cardiac arrest ~ 15–17 mg/dL.
| Classification | Range |
|---|---|
Therapeutic serum magnesium target | 4.8–8.4 mg/dL |
Calculates the total 24-hour magnesium sulfate dose for seizure prophylaxis in preeclampsia with severe features or eclampsia from the IV loading dose (4–6 g) and maintenance infusion rate (1–2 g/h) per ACOG (2020).
The total 24-hour dose equals the loading dose plus 24 × the maintenance rate (e.g., 4 g + 2 g/h = 52 g). The therapeutic serum magnesium range is 4.8–8.4 mg/dL; loss of patellar reflexes occurs near 10 mg/dL and respiratory depression near 12 mg/dL, treated with IV calcium gluconate.
Magnesium sulfate remains the standard of care for seizure prophylaxis in preeclampsia with severe features and for eclampsia, substantially reducing the risk of eclamptic seizures and associated mortality.
A patient with preeclampsia with severe features is started on the standard ACOG regimen: 4 g IV loading dose and a 2 g/h maintenance infusion.
Inputs:
Total 24-hour magnesium sulfate dose 52 g (4 g load + 2 g/h × 24 h); therapeutic serum magnesium 4.8–8.4 mg/dL.
Therapeutic serum magnesium is approximately 4.8–8.4 mg/dL (2–3.5 mEq/L). Levels above 10 mg/dL cause loss of deep tendon reflexes, and respiratory depression occurs near 12 mg/dL.
Most protocols continue therapy for 24 hours after delivery (or 24 hours after the last seizure), after which it is discontinued if severe features have resolved.
Disclaimer: This calculator is intended for educational and clinical decision support purposes only. Magnesium sulfate therapy requires individualized dosing, monitoring for toxicity, and prompt treatment of adverse effects.