MAGNESIUM SULFATE IN DEXTROSE 5% IN PLASTIC CONTAINER
Clinical safety rating
cautionComprehensive clinical and safety monograph for MAGNESIUM SULFATE IN DEXTROSE 5% IN PLASTIC CONTAINER (MAGNESIUM SULFATE IN DEXTROSE 5% IN PLASTIC CONTAINER).
Magnesium sulfate provides magnesium ions, which are essential for various physiological processes. It acts as a cofactor for enzymatic reactions, stabilizes excitable membranes, and antagonizes calcium entry at the neuromuscular junction, leading to reduced acetylcholine release and muscle relaxation. In the CNS, it may act as a noncompetitive antagonist of NMDA receptors, exerting anticonvulsant effects.
| Metabolism | Magnesium is not metabolized; it is primarily excreted unchanged by the kidneys via glomerular filtration and tubular reabsorption. Elimination half-life is approximately 4-6 hours in normal renal function. |
| Excretion | Primarily renal (90-100% as unchanged magnesium). Less than 1% biliary/fecal. |
| Half-life | Terminal half-life approximately 4-5 hours in normal renal function; prolonged in renal impairment (up to 40 hours). |
| Protein binding | Approximately 25-30% bound to albumin. |
| Volume of Distribution | 0.2-0.3 L/kg; distributes primarily in extracellular fluid. |
| Bioavailability | IV: 100%. Not administered orally for systemic effect due to poor GI absorption (<30%). |
| Onset of Action | IV: immediate (within seconds to minutes). |
| Duration of Action | IV: 30 minutes (anticonvulsant effect); continuous infusion required for sustained effect. |
| Molecular Weight | 246.47 |
1 to 4 g intravenously as a 5% to 20% solution, rate not exceeding 150 mg/min; dosing frequency depends on indication (e.g., preeclampsia/eclampsia: 4-5 g IV loading then 1-2 g/hr infusion; hypomagnesemia: 1-2 g IV over 1-2 hours, may repeat based on serum magnesium levels).
| Dosage form | INJECTABLE |
| Renal impairment | GFR 30-50 mL/min: reduce dose by 50% and monitor serum magnesium; GFR <30 mL/min: contraindicated or use extreme caution with dose reduction to 25% of normal and frequent monitoring. |
| Liver impairment | Child-Pugh A (mild): no specific adjustment; Child-Pugh B (moderate): use with caution, consider dose reduction; Child-Pugh C (severe): avoid use or reduce dose by 50% with close monitoring of magnesium levels and renal function. |
| Pediatric use | Loading dose: 20-40 mg/kg intravenously over 1-2 hours; maintenance: 10-20 mg/kg IV every 4-6 hours as needed; maximum infusion rate 150 mg/min; monitor serum magnesium during therapy. |
| Geriatric use | Reduce initial dose by 25-50% due to age-related decline in renal function; monitor serum magnesium and renal function closely; adjust dose based on GFR and clinical response. |
| 1st trimester | Magnesium sulfate crosses the placenta. Use caution; studies show increased risk of congenital abnormalities (e.g., skeletal defects) with prolonged use in first trimester. |
| 2nd trimester | Use with caution; monitor maternal serum magnesium levels. Risk of fetal hypocalcemia and skeletal abnormalities with prolonged therapy. |
| 3rd trimester | Approved for prevention of eclampsia; short-term use is generally safe. Prolonged infusion (>5 days) may cause fetal hypocalcemia and osteopenia. |
Clinical note
Comprehensive clinical and safety monograph for MAGNESIUM SULFATE IN DEXTROSE 5% IN PLASTIC CONTAINER (MAGNESIUM SULFATE IN DEXTROSE 5% IN PLASTIC CONTAINER).
| Placental transfer | Readily crosses the placenta; achieves fetal serum concentrations approximately equal to maternal levels. |
| Breastfeeding | Magnesium sulfate is excreted into breast milk in low concentrations. Levels are unlikely to cause adverse effects in the infant. However, caution with high maternal doses or prolonged therapy. |
| Lactation Rating | L2 (Safer) |
| Teratogenic Risk | Magnesium sulfate crosses the placenta and is not associated with major teratogenic effects when used for standard obstetric indications. Prolonged exposure (e.g., >5-7 days) in the second/third trimester may cause fetal hypocalcemia, skeletal abnormalities, or neonatal hypotonia. Continuous infusion near delivery may lead to neonatal respiratory depression and flaccidity. |
| Fetal Monitoring | Monitor maternal vital signs (BP, HR, RR), deep tendon reflexes, urine output, serum magnesium levels (therapeutic 4-8 mg/dL), and fetal heart rate tracing during continuous infusion. Watch for signs of magnesium toxicity (≥9 mg/dL): loss of DTRs, respiratory depression, altered consciousness. |
| Fertility Effects | No known adverse effects on fertility with short-term use. Long-term or high-dose exposure in animal studies suggests potential ovarian suppression, but human data are lacking. |
■ FDA Black Box Warning
WARNING: Do not administer undiluted intravenously. Continuous monitoring of serum magnesium levels, respiratory rate, deep tendon reflexes, and urine output is required. Hazardous infusion rates may cause respiratory arrest, cardiac arrest, or death.
| Serious Effects |
Hypersensitivity to magnesium sulfateHeart block or myocardial damageSerious renal impairment (creatinine clearance <20 mL/min) without dialysis
| Precautions | May cause respiratory depression or arrest if given too rapidly or in excessive doses., Use with caution in patients with renal impairment due to risk of accumulation and toxicity., Administer IV with caution in patients receiving digitalis glycosides; may cause heart block., Monitor deep tendon reflexes, respiratory rate, and urine output during infusion., Avoid concurrent use of neuromuscular blocking agents; may potentiate blockade., Use with caution in patients with myasthenia gravis or other neuromuscular disorders., Risk of hypotension, flushing, and bradycardia with rapid IV administration. |
| Food/Dietary | Avoid high-calcium or high-phosphate foods that may interfere with magnesium absorption. Limit alcohol and caffeine. No specific dietary restrictions beyond general healthy diet. |
| Clinical Pearls | Monitor serum magnesium levels closely, especially in renal impairment. Infusion site reactions (phlebitis) may occur; use central line for prolonged therapy. Calcium gluconate should be available as antidote for magnesium toxicity. Assess deep tendon reflexes before and during infusion; loss of patellar reflex indicates impending toxicity. Correct hypokalemia and hypocalcemia concomitantly to enhance magnesium retention. |
| Patient Advice | Report any flushing, sweating, or feeling of warmth during infusion. · Do not stop the medication abruptly; dose tapering may be needed. · Inform your doctor if you have kidney disease or are taking diuretics. · Avoid alcohol and caffeine, which can worsen electrolyte imbalances. · Stay hydrated but follow fluid restrictions if advised by your doctor. |
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