Magnesium%2520sulfate

# Magnesium sulfate ## Overview Magnesium sulfate is an electrolyte replacement agent and anticonvulsant. Parenteral administration provides rapid magnesium repletion or therapeutic effects for seizure prophylaxis/treatment. ## Primary Indications - Seizure prophylaxis/treatment in preeclampsia/eclampsia - Hypomagnesemia (severe or symptomatic) - Torsades de pointes (polymorphic ventricular tachycardia) - Acute severe asthma (adjunct, not first-line) - Prevention of cerebral palsy in preterm labor (neuroprotection) ## Adult Dosing **Preeclampsia/eclampsia (seizure prophylaxis/treatment):** - Loading dose: 4–6 g IV over 15–20 minutes - Maintenance: 1–2 g/hour IV continuous infusion - Duration: Usually 24 hours postpartum; local protocol may vary. **Severe hypomagnesemia:** - 1–4 g IV over 1–2 hours; repeat as needed based on serum levels. **Torsades de pointes:** - 1–2 g IV push (over 1–2 minutes); may repeat once after 5–15 minutes if needed. **Acute severe asthma (adjunct):** - 2 g IV over 20 minutes (single dose, not for routine use). **Maximum single dose:** Typically 4–6 g for loading; infusion rates vary. ## Pediatric Dosing **Seizure prophylaxis/treatment (eclampsia is rare in children; but for severe preeclampsia in adolescents):** - Dosing per local protocol; adult weight-based adjustments may apply. **Hypomagnesemia:** - 25–50 mg/kg/dose IV every 4–6 hours, up to 2 g/dose maximum (for severe depletion). **Torsades de pointes:** - 25–50 mg/kg IV push (max 2 g) over 1–2 minutes; may repeat once. **Acute severe asthma:** - 40–50 mg/kg/dose IV (max 2 g) over 20 minutes. ## Dose Adjustments - **Renal impairment:** Reduce dose by 25–50% if CrCl <30 mL/min; monitor serum magnesium and clinical status; avoid continuous infusion in severe renal failure unless titrated. - **Elderly:** Use caution; reduced renal function common; start at lower end of dosing range. ## Contraindications - Hypersensitivity to magnesium sulfate - Heart block (second- or third-degree AV block) or severe myocardial damage (relative) - Severe renal failure (anuria) unless dialysis available - Hypermagnesemia at baseline ## Adverse Effects - **Common:** Flushing, sweating, hypotension, nausea, muscle weakness - **Serious:** Respiratory depression (loss of deep tendon reflexes marks early toxicity), cardiac arrhythmia (bradycardia, heart block), cardiac arrest (at very high levels) - **Signs of toxicity:** Loss of patellar reflexes (4–7 mEq/L), respiratory depression (>7 mEq/L), cardiac arrest (>12 mEq/L) ## Key Drug Interactions - **Neuromuscular blocking agents:** Enhanced paralysis - **Calcium channel blockers (e.g., nifedipine):** Additive hypotension - **CNS depressants (barbiturates, opioids):** Increased sedation/respiratory depression - **Digoxin:** Increased risk of bradycardia/arrhythmias (if hypomagnesemic state corrected rapidly) - **Calcium gluconate:** Antidote for magnesium toxicity (IV calcium reverses neuromuscular/cardiac effects) ## Monitoring - **Serum magnesium:** Target 4–7 mg/dL for eclampsia; 1.5–2.5 mEq/L for replacement (check 2–6 hours after dosing) - **Deep tendon reflexes** (patellar): Assess hourly during infusion; loss indicates impending toxicity - **Respiratory rate, oxygen saturation** - **Vital signs** (BP, heart rate) - **Renal function** (serum creatinine, urine output) - **Continuous ECG** if used for torsades or arrhythmia ## Clinical Pearls - **Antidote:** Calcium gluconate (1 g IV over 3–5 min) for magnesium toxicity; repeat as needed. - **Infusion safety:** Use infusion pump; monitor for phlebitis; do not exceed 2 g/hour without close monitoring. - **Preeclampsia protocol may vary** by institution; confirm loading dose/infusion duration locally. - **Pediatric asthma:** Not first-line; reserve for severe exacerbation unresponsive to standard therapy. - **Subcutaneous/intramuscular** use is avoided due to pain, abscess risk. --- **Disclaimer:** This information is a concise summary for educational use. Dosing and administration may vary by clinical setting, local protocols, and patient-specific factors. Verify current prescribing information (e.g., manufacturer labeling, hospital guidelines, or drug reference) before use.