Magnesium Sulphate PK Simulator
Indication: Pre-eclampsia and Eclampsia (seizure prophylaxis)
Free interactive pharmacokinetic simulator for magnesium sulphate (MgSO₄) in pre-eclampsia and eclampsia. Based on Salinger et al. (2013) population PK model: 1-compartment, IV/IM dosing, body weight and serum creatinine covariates. Compare MAGPIE IV vs IM regimens, explore therapeutic window (2.0–3.5 mmol/L), and optimize seizure prophylaxis dosing.
Drug Overview
Clinical Context
- Molecular Target
- NMDA receptor antagonist / CNS depressant
- Drug Class
- Anticonvulsant / Electrolyte
- Therapeutic Area
- Obstetrics / Maternal Medicine
- Indication
- Pre-eclampsia and Eclampsia (seizure prophylaxis)
- Route of Administration
- IV, IM
Model Information
- Model Type
- PopPK — 1-Compartment, IV/IM
- Reference
- Salinger et al. (2013), BJOG 120:894–900
This simulator was built from published pharmacometric literature using PKPDBuilder's AI-powered model extraction pipeline.
Pharmacokinetic Parameters
PK Parameters
| Parameter | Value |
|---|---|
| CL | 4.81 L/h |
Additional Parameters
| Parameter | Value |
|---|---|
| V | 15.6 L |
| BL | 0.85 mmol/L (endogenous baseline) |
| F1 | 86.2% (IM bioavailability) |
| KA | 0.317 h⁻¹ (IM absorption) |
Parameters sourced from published population pharmacokinetic models. Values represent typical population estimates; individual patient parameters may vary.
🧬 Magnesium Sulphate in Pre-eclampsia: Clinical Background
Therapeutic Window: 2.0–3.5 mmol/L
Serum magnesium concentrations must be maintained within a narrow therapeutic window for effective seizure prophylaxis while avoiding toxicity. The simulator shades three zones on the concentration-time plot:
| Level (mmol/L) | mg/dl | mEq/L | Clinical Significance |
|---|---|---|---|
| < 2.0 | < 4.8 | < 4 | Potentially sub-therapeutic |
| 2.0–3.5 | 4.8–8.5 | 4–7 | ✅ Therapeutic (seizure prophylaxis) |
| 3.5–5.0 | 8.5–12 | 7–10 | ⚠️ Loss of patellar reflexes |
| 5.0–6.5 | 12–15.8 | 10–13 | 🚨 Respiratory paralysis risk |
| > 7.5 | > 18 | > 15 | ❌ Cardiac conduction changes |
Note: 1 mmol/L ≈ 2.43 mg/dl ≈ 2 mEq/L for Mg²⁺. Antidote: calcium gluconate 1 g IV.
MAGPIE Trial Standard Protocols
💉 IV Protocol
- Loading: 4 g IV over 20 minutes
- Maintenance: 1 g/h continuous infusion
- Achieves: Rapid therapeutic levels
- Monitoring: Continuous
💊 IM Protocol
- Loading: 4 g IV + 10 g IM (5 g each gluteal)
- Maintenance: 5 g IM Q4H
- Bioavailability: ~86% (F = 0.862)
- Use when: IV access limited
Clinical monitoring before each dose: deep tendon reflexes (must be present), respiratory rate (≥12/min), urine output (≥25 mL/h). Serum Mg levels should be checked if toxicity is suspected.
📊 Population PK Model — Salinger et al. (2013)
This simulator implements the population pharmacokinetic model published by Salinger et al. (2013) in BJOG, derived from 258 pregnant women with pre-eclampsia enrolled in the Magpie Trial (India cohort). The model was fit using NONMEM 7 with mixed-effects modeling and proportional residual error.
| Parameter | Value | Units | %RSE |
|---|---|---|---|
| Clearance (CL) | 4.81 | L/h | 10% |
| Volume of distribution (V) | 15.6 | L | 8% |
| IM absorption rate (Kₐ) | 0.317 | h⁻¹ | 16% |
| IM bioavailability (F) | 86.2% | — | 3.2% |
| Endogenous baseline (BL) | 0.85 | mmol/L | — |
| Residual CV | 22.9% | — | — |
Covariate Effects
V_i = 15.6 × (WT/55)^0.692CL_i = 4.81 × (0.8/SCr)^1.48Reference: WT = 55 kg (study median) | SCr = 0.8 mg/dl
About This Simulator
This interactive pharmacokinetic simulator for Magnesium Sulphate allows you to explore concentration-time profiles under different dosing scenarios. The underlying PopPK — 1-Compartment, IV/IM model characterizes the pharmacokinetics of this anticonvulsant / electrolyte following iv, im administration.
Use the simulator to visualize key exposure metrics including AUC (area under the curve), Cmax (peak concentration), and Ctrough (trough concentration).
Built with PKPDBuilder — an AI-powered platform that transforms published pharmacometric literature into interactive, deployable Shiny applications. No coding required.
Frequently Asked Questions
What is the therapeutic range for magnesium sulphate in pre-eclampsia?
The therapeutic serum magnesium range for seizure prophylaxis in pre-eclampsia is 2.0–3.5 mmol/L (4.8–8.5 mg/dl, or 4–7 mEq/L). Levels below 2.0 mmol/L may be sub-therapeutic, while levels above 3.5 mmol/L carry increasing risk of toxicity: loss of deep tendon reflexes occurs at 3.5–5.0 mmol/L, respiratory paralysis risk at 5.0–6.5 mmol/L, and cardiac conduction changes at >7.5 mmol/L. Calcium gluconate (1 g IV) is the antidote for overdose.
What is the difference between IV and IM magnesium sulphate regimens?
Both the IV and IM regimens (the MAGPIE protocol) are used for eclampsia prevention, but they differ pharmacokinetically. The IV regimen (4 g loading over 20 min + 1 g/h maintenance) produces faster, higher peak concentrations. The IM regimen (4 g IV + 10 g IM loading + 5 g IM Q4H) produces a lower, sustained release due to the depot absorption from muscle, with IM bioavailability of ~86% and absorption rate constant Ka ≈ 0.317 h⁻¹. The Salinger et al. (2013) population PK study showed that despite different concentration-time profiles, both regimens can achieve therapeutic magnesium concentrations when dosed appropriately.
How does body weight affect magnesium sulphate pharmacokinetics?
Body weight significantly influences the volume of distribution of magnesium sulphate. In the Salinger et al. (2013) population PK model, volume of distribution scales with body weight as: V_i = 15.6 L × (WT/55 kg)^0.692. This means heavier patients have larger volumes of distribution, resulting in lower peak concentrations for the same dose. The reference weight in this model is 55 kg (median for the study population of 258 Indian pregnant women). The simulator adjusts V automatically when you change body weight.
How does renal function affect magnesium sulphate dosing?
Magnesium is almost exclusively eliminated by renal filtration with no significant hepatic metabolism. Clearance is proportional to glomerular filtration rate. In the Salinger (2013) model, clearance scales with serum creatinine as: CL_i = 4.81 L/h × (0.8/SCr)^1.48, where 0.8 mg/dl is the reference creatinine. Impaired renal function (higher SCr) significantly reduces magnesium clearance, prolonging half-life and increasing accumulation risk. Patients with renal impairment require dose reduction and closer monitoring of deep tendon reflexes, respiratory rate, and urine output.
What is the MAGPIE trial protocol for magnesium sulphate?
The Magpie Trial (2002) established magnesium sulphate as the gold standard for eclampsia prevention, showing 58% reduction in eclampsia risk vs. placebo. The standard MAGPIE IV protocol is: 4 g IV loading dose over 20 minutes, followed by 1 g/h continuous IV maintenance infusion. The IM protocol (used where IV access is limited): 4 g IV load + 10 g IM loading (5 g each gluteal) + 5 g IM Q4H. Clinical monitoring should include deep tendon reflexes (must be present), respiratory rate (≥12/min), and urine output (≥25 mL/h) before each dose.
What is the Magnesium Sulphate PK simulator?
This is a free, interactive pharmacokinetic simulator for Magnesium Sulphate used in Pre-eclampsia and Eclampsia (seizure prophylaxis). It allows researchers, pharmacologists, and students to explore concentration-time profiles, dosing regimens, and exposure metrics based on published population PK models.
What drug class does Magnesium Sulphate belong to?
Magnesium Sulphate is classified as a Anticonvulsant / Electrolyte that targets NMDA receptor antagonist / CNS depressant. It is used in the Obstetrics / Maternal Medicine therapeutic area.
What route of administration does this model simulate?
This simulator models IV, IM administration of Magnesium Sulphate. The pharmacokinetic parameters (absorption rate, bioavailability, volume of distribution) are specific to this route.
What type of PK model is used?
This simulator uses a PopPK — 1-Compartment, IV/IM model. Population PK models account for interindividual variability and covariate effects on drug exposure.
Is this simulator free to use?
Yes, all PKPDBuilder simulators are completely free. They are built from published pharmacokinetic literature and are intended for research and educational purposes. No login is required to run simulations.
Can I use this for clinical dosing decisions?
No. This simulator is for research and educational purposes only. It should not be used for clinical decision-making or patient dosing. Always consult the prescribing information and clinical pharmacology guidelines for therapeutic drug use.
What is the half-life of Magnesium Sulphate?
Based on the published model parameters, the elimination half-life of Magnesium Sulphate is approximately ~2.2 h. Note that half-life can vary based on patient-specific factors such as body weight, organ function, and genetic polymorphisms.
What is the clearance of Magnesium Sulphate?
The clearance (CL) of Magnesium Sulphate is approximately 4.81 L/h. Clearance represents the volume of plasma from which drug is completely removed per unit time and is a key determinant of drug exposure and steady-state concentrations.
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⚠️ Disclaimer
This simulator is for research and educational purposes only. It is not intended for clinical decision-making, patient dosing, or therapeutic drug monitoring. Pharmacokinetic parameters are derived from published literature and represent population-level estimates. Individual patient pharmacokinetics may differ significantly. Always consult approved prescribing information and qualified healthcare professionals for clinical decisions.
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