magnesium sulfate (Rx)

Frequency Not Defined

Circulatory collapse

Respiratory paralysis

Hypothermia

Pulmonary edema

Depressed reflexes

Hypotension

Flushing

Drowsiness

Depressed cardiac function

Diaphoresis

Hypocalcemia

Hypophosphatemia

Hyperkalemia

Visual changes

Contraindications

Hypersensitivity

Myocardial damage, diabetic coma, heart block

Hypermagnesemia

Hypercalcemia

Administration during 2 hours preceding delivery for mothers with toxemia of pregnancy

Cautions

Fetal skeletal demineralization, hypocalcemia, and hypermagnesemia abnormalities reported with continuous long-term use (ie, longer than 5-7 days) for off-label treatment of preterm labor in pregnant women; the effect on the developing fetus may result in neonates with skeletal abnormalities

In patients with renal impairment, ensure that renal excretory capacity is not exceeded

Use with caution in digitalized patients

Use with extreme caution in patients with myasthenia gravis or other neuromuscular disease

Hypomagnesemia is usually associated with hypokalemia (potassium levels must be normalized)

Monitor renal function, blood pressure, respiratory rate, and deep tendon reflex when magnesium sulfate is administered parenterally

Pregnancy category: D

Fetal skeletal demineralization, hypocalcemia, and hypermagnesemia reported with continuous long-term use (ie, longer than 5-7 days) for off-label treatment of preterm labor in pregnant women; the effect on the developing fetus may result in neonates with skeletal abnormalities

Continuous administration of magnesium sulfate injection to treat preterm labor is not approved and that the safety and efficacy of use for this indication are not established

Lactation: Safe

Pregnancy Categories

A: Generally acceptable. Controlled studies in pregnant women show no evidence of fetal risk.

B: May be acceptable. Either animal studies show no risk but human studies not available or animal studies showed minor risks and human studies done and showed no risk.

C: Use with caution if benefits outweigh risks. Animal studies show risk and human studies not available or neither animal nor human studies done.

D: Use in LIFE-THREATENING emergencies when no safer drug available. Positive evidence of human fetal risk.

X: Do not use in pregnancy. Risks involved outweigh potential benefits. Safer alternatives exist.

NA: Information not available.

Mechanism of Action

Depresses CNS, blocks peripheral neuromuscular transmission, produces anticonvulsant effects; decreases amount of acetylcholine released at end-plate by motor nerve impulse

Slows rate of SA node impulse formation in myocardium and prolongs conduction time

Promotes movement of calcium, potassium, and sodium in and out of cells and stabilizes excitable membranes

Promotes osmotic retention of fluid in colon, causing distention and increased peristaltic activity, which subsequently results in bowel evacuation

Absorption

Onset (anticonvulsant): IV, immediate; IM, 1 hr

Duration (anticonvulsant): IV, 30 min; IM, 3-4 hr

Distribution

Protein bound: 30%

Extracellular distribution: 1-2%

Elimination

Excretion: Urine

IV Incompatibilities

Solution: IV fat emulsion 10%

Additive: Amphotericin B, cyclosporine, dobutamine, polymyxin B sulfate, procaine, sodium bicarbonate

Y-site: Alatrofloxacin, amiodarone (at 500 mg/mL MgSO4; may be compatible at 20 mg/mL), amphotericin B cholesteryl sulfate, cefepime, ciprofloxacin (?)

IV Preparation

Intermittent infusion: Dilute to 60 mg/mL

IV Administration

Infuse over 2-4 hr (hypomagnesemia) or as otherwise specified; rate not to exceed 125 mg/kg/hr

In severe cases, half of the dose may be infused over first 15-20 minutes

Rapid infusions (over 10-20 minutes) may be used for treatment of severe asthma or torsades de pointes ventricular tachycardia

Cautiously infuse diluted solution through patent IV line

IM Administration

Dilute to maximum concentration of 200 mg/mL before injection