Schedule H

Intravenous (IV), Intramuscular (IM)

• Injection: 50% w/v solution (500 mg/mL) in 2 mL ampoule (1 g total)

• Injection: 50% w/v solution (500 mg/mL) in 10 mL ampoule (5 g total)

INDICATIONS + DOSING — FOR CLINICIAN USE ONLY

Primary Indications (Approved / Standard in India)

1. Eclampsia and Severe Pre-Eclampsia — Seizure Prophylaxis and Treatment

Pritchard Regimen (IM-Based — Standard in India)

Step Dose Clinical Notes

Starting dose (Loading) 4 g IV over 5–10 minutes PLUS 10 g IM (5 g deep IM into each buttock) Dilute IV dose to 20% solution; mix IM dose with 1 mL 2% lignocaine to reduce pain

Titration Not applicable Fixed protocol

Usual maintenance dose 5 g IM into alternate buttock every 4 hours Continue for 24 hours after last seizure or delivery (whichever is later)

Maximum dose Loading: 14 g; Maintenance: 5 g per dose Total dependent on duration of therapy

Zuspan Regimen (IV-Only — Alternative)

Step Dose Clinical Notes

Starting dose (Loading) 4 g IV over 15–20 minutes Dilute to 20% solution (8 mL of 50% + 12 mL NS)

Titration Not applicable Fixed protocol

Usual maintenance dose 1–2 g/hour continuous IV infusion Use infusion pump; continue for 24 hours post-delivery or last seizure

Maximum dose 2 g/hour infusion Higher rates increase toxicity risk

Key points:

• Drug of choice for eclampsia/severe pre-eclampsia as per MoHFW/WHO/ICMR guidelines

• Check reflexes, respiratory rate (>12/min), and urine output (>30 mL/hour) before EACH maintenance dose

• Target serum Mg²⁺: 4–7 mEq/L (2–3.5 mmol/L or 4.8–8.4 mg/dL)

• Keep 10% calcium gluconate 10 mL ready at bedside as antidote

1. Torsades de Pointes (Polymorphic Ventricular Tachycardia with Prolonged QT)

Intravenous Route

Step Dose Clinical Notes

Starting dose 1–2 g IV over 5–20 minutes Dilute in 50–100 mL NS or D5W

Titration May repeat if arrhythmia recurs Based on ECG response

Usual maintenance dose 0.5–1 g/hour IV infusion (if recurrent) For refractory cases

Maximum dose 2 g bolus; infusion based on clinical response

Key points:

• Effective even in patients with normal serum magnesium

• First-line treatment for torsades regardless of magnesium status

• Continue cardiac monitoring throughout

1. Severe/Symptomatic Hypomagnesaemia (Serum Mg²⁺ <1.2 mg/dL or <0.5 mmol/L)

Intravenous Route

Step Dose Clinical Notes

Starting dose 1–2 g (2–4 mL of 50% solution) IV over 30–60 minutes Dilute in 100 mL NS or D5W

Titration Based on serum Mg²⁺ levels Check levels 6–12 hours after loading

Usual maintenance dose 1 g IV every 6–12 hours Adjust based on serum levels and renal function

Maximum dose 12 g in 24 hours Higher doses in severe deficiency under monitoring

1. Fetal Neuroprotection in Preterm Labour (<32 Weeks Gestation)

Intravenous Route

Step Dose Clinical Notes

Starting dose 4 g IV over 20–30 minutes Administer when preterm delivery imminent

Titration Not applicable Fixed regimen

Usual maintenance dose 1 g/hour continuous IV infusion Continue until delivery or maximum 24 hours

Maximum dose 4 g loading + 24 g maintenance (over 24 hours)

Key points:

• Reduces risk of cerebral palsy in preterm infants

• Recommended by ICMR and select tertiary obstetric protocols

• Monitor for maternal toxicity signs

Secondary Indications — Adults (Off-label)

Indication Dose Duration Notes

Acute Severe Asthma (Refractory to bronchodilators) 2 g IV over 20 minutes Single dose; may repeat once OFF-LABEL; ER/ICU specialist only; Evidence: Meta-analyses (Cochrane); Indian ER protocols at tertiary centres

Tetanus (adjunct for muscle spasm control) 4 g IV loading then 2–3 g/hour infusion Until spasm control achieved OFF-LABEL; ICU specialist only; Evidence: Case series; used when diazepam/baclofen inadequate

PAEDIATRIC DOSING (Specialist Only)

Primary Indications

1. Severe/Symptomatic Hypomagnesaemia

Intravenous Route — Weight-Based

Step Dose Clinical Notes

Starting dose 25–50 mg/kg IV over 30–60 minutes Dilute appropriately; maximum 2 g per dose

Titration Based on serum Mg²⁺ levels Recheck 6–12 hours after loading

Usual maintenance dose 25–50 mg/kg IV every 8–12 hours Duration based on underlying cause

Maximum dose 2 g per single dose

1. Torsades de Pointes

Intravenous Route — Weight-Based

Step Dose Clinical Notes

Starting dose 25–50 mg/kg IV over 10–20 minutes Maximum 2 g per dose

Titration May repeat once if arrhythmia persists

Usual maintenance dose Not applicable Single-dose intervention

Maximum dose 2 g total

Safety monitoring:

• Continuous cardiac monitoring

• Frequent assessment of deep tendon reflexes

• Respiratory rate monitoring

• Renal function assessment

Secondary Indications — Paediatrics (Off-label)

Indication Dose Duration Notes

Acute Severe Asthma (refractory to bronchodilators) 25–50 mg/kg IV over 20 minutes (max 2 g) Single dose OFF-LABEL; PICU specialist only; Evidence: Paediatric RCTs; limited Indian data

Minimum age: Not recommended in infants <6 months except under neonatologist/paediatric intensivist supervision

eGFR <15 or dialysis Avoid unless life-threatening indication (eclampsia, torsades); significant accumulation risk; monitor Mg²⁺ before each dose

Notes:

• Magnesium is primarily renally excreted (>95%)

• Haemodialysis removes magnesium effectively

• In eclampsia with oliguria: Continue therapy but omit maintenance dose if urine output <30 mL/hour; monitor reflexes carefully

Note: Magnesium is not hepatically metabolised; dose adjustment determined by renal function only

• Heart block (second or third-degree AV block without pacemaker)

• Myasthenia gravis

• Severe renal failure with oliguria/anuria (relative — may use with caution in eclampsia)

• Untreated hypocalcaemia

• Known hypersensitivity to magnesium sulphate

• Diabetic coma

• Within 2 hours of delivery if neonatal resuscitation facilities not available (for obstetric use)

• Mild-to-moderate renal impairment — risk of accumulation; adjust dose and monitor closely

• Elderly patients — increased susceptibility to CNS depression

• Concurrent calcium channel blockers — additive hypotension and neuromuscular blockade

• Concurrent use of other CNS depressants

• Respiratory disease — may worsen respiratory depression

• Neuromuscular disorders (other than myasthenia gravis)

• Digitalis therapy — monitor for AV block

• Rapid IV administration — risk of flushing, hypotension, bradycardia

Parameter Recommendation

Safety category Drug of choice for eclampsia and severe pre-eclampsia; extensive safety data

Preferred alternatives No alternatives for seizure prophylaxis in eclampsia — MgSO₄ is standard of care

When it may be used Eclampsia; severe pre-eclampsia; imminent preterm delivery (<32 weeks) for neuroprotection

Monitoring Maternal: Deep tendon reflexes hourly; respiratory rate (>12/min); urine output (>30 mL/hour); BP; Fetal: Continuous fetal heart rate monitoring

Notes:

• Crosses placenta; transient neonatal hypotonia and respiratory depression possible

• Prolonged use (>5–7 days) may cause fetal bone abnormalities — limit duration

• Continue monitoring for 24 hours after last dose

Parameter Recommendation

Compatibility Compatible with breastfeeding

Drug levels in milk Low (increases slightly during therapy but not clinically significant)

Preferred alternatives Not required — safe during breastfeeding

Infant monitoring Observe for diarrhoea or sedation (rare); routine monitoring usually sufficient

• Recommended starting dose: Use lower end of dosing range; standard loading dose for emergencies but with enhanced monitoring

• Titration: Slower; more frequent clinical assessment

• Additional risks:

• Higher risk of CNS depression (lethargy, confusion)

• Age-related decline in renal function — calculate/estimate GFR; adjust accordingly

• Increased susceptibility to hypotension

• Higher risk of respiratory depression

• Monitoring: Reflexes, respiratory rate, BP, and renal function before each dose

Drug Interaction Management

Neuromuscular blocking agents (vecuronium, rocuronium, atracurium) Prolonged and enhanced neuromuscular blockade Reduce dose of neuromuscular blocker; use with caution; ensure availability of reversal agents

Calcium salts (IV calcium gluconate/chloride) Pharmacological antagonism; chemical precipitation if mixed Do NOT mix in same line; keep calcium gluconate available as ANTIDOTE for magnesium toxicity

CNS depressants (opioids, benzodiazepines, barbiturates) Additive CNS and respiratory depression Use with caution; reduce doses; enhanced monitoring

Digoxin Increased risk of AV block with hypermagnesaemia Monitor ECG; caution with high magnesium doses

Drug Interaction Management

Calcium channel blockers (nifedipine, amlodipine) Additive hypotension; enhanced neuromuscular blockade Common combination in pre-eclampsia; monitor BP closely; avoid sublingual nifedipine

Loop diuretics (furosemide) Increased renal magnesium wasting → hypomagnesaemia Monitor serum Mg²⁺; may need supplementation

Thiazide diuretics Increased renal magnesium wasting Monitor serum Mg²⁺

Aminoglycoside antibiotics (gentamicin, amikacin) Additive neuromuscular blockade Use with caution; monitor neuromuscular function

Amphotericin B Increases renal magnesium wasting Monitor serum Mg²⁺

Quinolone and tetracycline antibiotics (oral) Reduced antibiotic absorption if taken with oral magnesium Separate administration by 2–4 hours (relevant only for oral use)

• Flushing and sensation of warmth

• Nausea and vomiting (especially with rapid IV)

• Hypotension

• Injection site pain (IM route)

• Dizziness

• Muscle weakness

• Diminished deep tendon reflexes (at therapeutic levels)

• Diaphoresis

Reaction Action Required

Respiratory depression (respiratory rate <12/min) STOP infusion immediately; administer calcium gluconate 10% 10 mL IV over 3 minutes; supportive ventilation if needed

Cardiac arrest / Asystole (at very high levels >15 mEq/L) STOP infusion; CPR; calcium gluconate 10% 10–20 mL IV; advanced cardiac life support

Severe hypotension STOP or slow infusion; IV fluids; calcium gluconate if refractory

Complete heart block STOP infusion; calcium gluconate; temporary pacing may be required

Pulmonary oedema STOP infusion; diuretics; oxygen; supportive care

Loss of deep tendon reflexes (early toxicity sign) Withhold next dose; recheck reflexes; resume only when reflexes return

Antidote: Calcium gluconate 10% — 10 mL IV over 3 minutes; keep at bedside for ALL patients receiving MgSO₄

Before EACH maintenance dose Deep tendon reflexes (patellar); respiratory rate (must be >12/min); urine output (must be >30 mL/hour over preceding 4 hours)

During IV infusion Continuous cardiac monitoring in ICU/CCU settings; hourly BP and respiratory rate

Serum Mg²⁺ levels Every 4–6 hours if on IV infusion >12 hours; target 4–7 mEq/L (4.8–8.4 mg/dL)

Post-therapy Continue monitoring for 24 hours after last dose; watch for delayed toxicity in renal impairment

Clinical toxicity thresholds:

• 4–7 mEq/L: Therapeutic range

• 7–10 mEq/L: Loss of deep tendon reflexes

• 10–15 mEq/L: Respiratory depression

• 15 mEq/L: Cardiac arrest

Single-ingredient products:

• Magnesium Sulphate Injection IP (government supply — multiple PSU manufacturers)

• Magneon (Neon)

• Magmin (Abbott)

• MGSO4 (Cadila)

• Magsulf (Samarth Pharma)

Note: Widely available through government supply chains for maternal health facilities; included in essential drug kits for obstetric emergencies

NLEM status: Magnesium Sulphate Injection 50% is included in NLEM 2022 — ceiling price applicable under NPPA

Government supply: Available free through JSY (Janani Suraksha Yojana) and NHM maternal health programmes at all public health facilities

• Always have calcium gluconate ready: Keep 10% calcium gluconate 10 mL at bedside for ALL patients receiving MgSO₄; this is the antidote for toxicity

• Clinical monitoring beats serum levels: In resource-limited settings, check reflexes, respiratory rate, and urine output before each dose — laboratory Mg²⁺ levels are helpful but not essential

• IM injections are painful: Always mix with 1 mL of 2% lignocaine for deep IM injection; use Z-track technique

• Dilute for IV use: 50% solution is too concentrated for IV bolus; dilute to 20% (add 8 mL of 50% to 12 mL NS for 20 mL of 20% solution)

• Stop if reflexes absent: Loss of patellar reflex is early warning of toxicity — withhold dose and reassess

• Avoid in myasthenia gravis: Absolutely contraindicated — worsens muscle weakness

magnesium sulphate; eclampsia; pre-eclampsia; obstetric emergency; anticonvulsant; torsades de pointes; hypomagnesaemia; neuroprotection; NLEM India; government supply

RxIndia v1.1 — 14 Jun 2025

• CDSCO Approved Product Information

• Indian Pharmacopoeia 2022

• National Formulary of India 2021

• NLEM 2022 (National List of Essential Medicines)

• MoHFW Guidelines on Prevention and Management of Pre-eclampsia and Eclampsia

• ICMR Guidelines on Pre-eclampsia and Eclampsia

• FOGSI Good Clinical Practice Recommendations

• AIIMS Obstetrics Protocols

• API Textbook of Medicine (11th Edition)

• IAP Guidelines (Paediatric Critical Care)

• Goodman & Gilman's The Pharmacological Basis of Therapeutics (13th Edition)

• Magpie Trial (Lancet 2002) — Eclampsia prevention

• BEAM Trial (NEJM 2008) — Fetal neuroprotection (for off-label preterm neuroprotection reference)