magnesium sulfate (parenteral)

Contraindicated in:

Hypermagnesemia;
Hypocalcemia;
Anuria;
Heart block.

Use Cautiously in:

Renal impairment;
OB: Avoid using for more than 5–7 days for preterm labor (may ↑ risk of hypocalcemia and bone changes in newborn); avoid continuous use during active labor or within 2 hr of delivery due to potential for magnesium toxicity in newborn;
Geri: Older adults may require ↓ dosage due to age-related ↓ in renal function.

Adv. Reactions/Side Effects ⬆ ⬇

CV: arrhythmias, bradycardia, hypotension

Derm: flushing, sweating

GI: diarrhea

Metab: hypothermia

MS: muscle weakness

Neuro: drowsiness

Resp: ↓respiratory rate

Interactions ⬆ ⬇

Drug-drug:

May potentiate calcium channel blockers and neuromuscular blocking agents.

Availability ⬆ ⬇

(Generic available)

Solution for injection (8.1 mEq Mg/g): 500 mg/mL (50%)
Premixed infusion: 1 g/100 mL; 2 g/50 mL; 4 g/50 mL; 4 g/100 mL; 20 g/500 mL; 40 g/1000 mL

Route/Dosage ⬆ ⬇

Treatment of Deficiency

IM IV (Adults ): Severe deficiency: 8–12 g/day in divided doses; Mild deficiency: 1 g every 6 hr for 4 doses or 250 mg/kg over 4 hr.
IM IV (Children >1 mo): 25–50 mg/kg/dose every 4–6 hr for 3–4 doses (max single dose = 2 g).
IV (Neonates ): 25–50 mg/kg/dose every 8–12 hr for 2–3 doses.

Seizures Associated with Eclampsia/Pre-Eclampsia

IV (Adults ): 4–6 g loading dose over 15–30 min at onset of labor or induction/cesarean delivery, followed by 1–2 g/hr continuous infusion for ≥24 hr after delivery (max infusion rate = 3 g/hr). If seizure occurs while receiving magnesium, an additional bolus of 2–4 g may be administered over ≥5 minutes. Max dose = 40 g/24 hr.
IM (Adults ): 10 g loading dose administered as 5 g in each buttock at onset of labor or induction/cesarean delivery, followed by 5 g every 4 hr for ≥24 hr after delivery.

Torsades de Pointes

IV (Adults ): 1–2 g over 15 minutes. If no response or torsades de pointes recurs, may repeat dose up to a total of 4 g in 1 hour; may follow with a continuous IV infusion of 0.5–1 g/hr.
IV (Infants and Children): 25–50 mg/kg/dose (max dose = 2 g).

Bronchodilation

IV (Adults ): 2 g single dose.
IV (Children ): 25 mg/kg/dose (max dose = 2 g).

Parenteral Nutrition

IV (Adults ): 4–24 mEq/day.
IV (Children ): 0.25–0.5 mEq/kg/day.

Action ⬆ ⬇

Essential for the activity of many enzymes.
Plays an important role in neurotransmission and muscular excitability.

Therapeutic effects:

Replacement in deficiency states.
Resolution of eclampsia.

Classifications ⬆ ⬇

Therapeutic Classification: mineral and electrolyte replacements/supplements

Pharmacologic Classification: minerals electrolytes

Pharmacokinetics ⬆ ⬇

Absorption: IV administration results in complete bioavailability; well absorbed from IM sites.

Distribution: Widely distributed to tissues

Metabolism/Excretion: Excreted primarily by the kidneys.

Half-Life: Unknown.

Time/Action Profile ⬆ ⬇

(anticonvulsant effect)

ROUTE	ONSET	PEAK	DURATION
IM	60 min	unknown	3–4 hr
IV	immediate	unknown	30 min

Patient/Family Teaching ⬆ ⬇

Explain purpose of medication to patient and family.
Rep: Monitor vital signs, oxygen saturation, respiration, deep tendon reflexes, level of consciousness, fetal heart rate, maternal uterine activity, and renal function when used during pregnancy. Monitor magnesium concentrations every 4 hr in patients with renal dysfunction (every 2 hr if serum magnesium is elevated). Breast milk concentrations are increased for only 24 hr after end of therapy. When used for prevention of seizures, magnesium sulfate is considered compatible with breastfeeding.

section name header

Indications ⬇

Contraind./Precautions ⬆ ⬇