Magnesium Chloride

Pronunciation

(mag NEE zhum KLOR ide)

Dosage Forms

Excipient information presented when available (limited, particularly for generics); consult specific product labeling. [DSC] = Discontinued product

Solution, Injection, as hexahydrate:

Chloromag: 200 mg/mL (50 mL) [contains benzyl alcohol]

Generic: 200 mg/mL (50 mL)

Tablet Delayed Release, Oral:

Mag-SR Plus Calcium: 535 mg (elemental magnesium 64 mg, plus calcium 106 mg) [starch free, sugar free]

Magdelay: Elemental magnesium 70 mg (plus calcium 118 mg)

Nu-Mag: Elemental magnesium 71.5 mg (plus calcium 119 mg) [contains fd&c blue #2 aluminum lake]

Slow Magnesium/Calcium: 535 mg (elemental magnesium 64 mg, plus calcium 106 mg)

Slow-Mag: Elemental magnesium 71.5 mg (plus calcium 119 mg) [contains fd&c blue #2 aluminum lake]

Tablet Extended Release, Oral:

Mag-SR: 535 mg (elemental magnesium 64 mg) [DSC] [starch free, sugar free]

Brand Names: U.S.

• Chloromag
• Mag-SR Plus Calcium [OTC]
• Mag-SR [OTC] [DSC]
• Magdelay [OTC]
• Nu-Mag [OTC]
• Slow Magnesium/Calcium [OTC]
• Slow-Mag [OTC]

Pharmacologic Category

• Electrolyte Supplement, Oral
• Electrolyte Supplement, Parenteral
• Magnesium Salt

Pharmacology

Magnesium is important as a cofactor in many enzymatic reactions in the body involving protein synthesis and carbohydrate metabolism (at least 300 enzymatic reactions require magnesium). Actions on lipoprotein lipase have been found to be important in reducing serum cholesterol and on sodium/potassium ATPase in promoting polarization (eg, neuromuscular functioning).

Absorption

Oral: Inversely proportional to amount ingested; 40% to 60% under controlled dietary conditions; 15% to 36% at higher doses

Distribution

Bone (50% to 60%); extracellular fluid (1% to 2%)

Excretion

Urine (as magnesium)

Protein Binding

30%, to albumin

Use: Labeled Indications

Correction or prevention of hypomagnesemia; dietary supplement

Contraindications

Hypersensitivity to any component of the formulation; renal impairment; myocardial disease; coma

Dosing: Adult

Note: Serum magnesium is poor reflection of repletional status as the majority of magnesium is intracellular; serum levels may be transiently normal for a few hours after a dose is given; therefore, aim for consistently high normal serum levels in patients with normal renal function for most efficient repletion.

Dietary supplement: Oral (Mag 64, Mag-Delay, Slow-Mag): 2 tablets once daily

Hypomagnesemia, prevention (parenteral nutrition supplementation) (ASPEN [Mirtallo 2004]): IV (elemental magnesium): 8 to 20 mEq/day

RDA (elemental magnesium) (IOM 1997): Oral:

19 to 30 years:

Females: 310 mg/day

Pregnancy: 350 mg/day

Lactation: 310 mg/day

Males: 400 mg/day

≥31 years:

Females: 320 mg/day

Pregnancy: 360 mg/day

Lactation: 320 mg/day

Males: 420 mg/day

Dosing: Geriatric

Refer to adult dosing.

Dosing: Pediatric

Note: Serum magnesium is poor reflection of repletional status as the majority of magnesium is intracellular; serum levels may be transiently normal for a few hours after a dose is given; therefore, aim for consistently high normal serum levels in patients with normal renal function for most efficient repletion.

Infants, Children, and Adolescents:

Hypomagnesemia, prevention (parenteral nutrition supplementation) (ASPEN [Mirtallo, 2004]): IV (elemental magnesium):

≤50 kg: 0.3 to 0.5 mEq/kg/day

>50 kg: 10 to 30 mEq/day

RDA (elemental magnesium) (IOM, 1997): Oral:

1 to 3 years: 80 mg/day

4 to 8 years: 130 mg/day

9 to 13 years: 240 mg/day

14 to 18 years:

Females: 360 mg/day

Pregnancy: 400 mg/day

Lactation: 360 mg/day

Males: 410 mg/day

Dosing: Renal Impairment

According to the manufacturer’s labeling, use is contraindicated in patients with renal impairment

Dosing: Hepatic Impairment

No dosage adjustment provided in manufacturer’s labeling.

Reconstitution

Dilute magnesium chloride 4 g in 250 mL D₅W.

Dietary Considerations

Whole grains, legumes, and dark-green leafy vegetables are dietary sources of magnesium.

Storage

Injection: Prior to reconstitution, store at controlled room temperature of 15°C to 30°C (59°F to 86°F).

Drug Interactions

Alfacalcidol: May increase the serum concentration of Magnesium Salts. Consider therapy modification

Alpha-Lipoic Acid: Magnesium Salts may decrease the absorption of Alpha-Lipoic Acid. Alpha-Lipoic Acid may decrease the absorption of Magnesium Salts. Consider therapy modification

Bisphosphonate Derivatives: Magnesium Salts may decrease the serum concentration of Bisphosphonate Derivatives. Management: Avoid administration of oral magnesium salts within: 2 hours before or after tiludronate/clodronate/etidronate; 60 minutes after oral ibandronate; or 30 minutes after alendronate/risedronate. Exceptions: Pamidronate; Zoledronic Acid. Consider therapy modification

Calcitriol (Systemic): May increase the serum concentration of Magnesium Salts. Management: Consider using a non-magnesium-containing antacid or phosphate-binding product in patients also receiving calcitriol. If magnesium-containing products must be used with calcitriol, serum magnesium concentrations should be monitored closely. Consider therapy modification

Calcium Channel Blockers: May enhance the adverse/toxic effect of Magnesium Salts. Magnesium Salts may enhance the hypotensive effect of Calcium Channel Blockers. Monitor therapy

Deferiprone: Magnesium Salts may decrease the serum concentration of Deferiprone. Management: Separate administration of deferiprone and oral medications or supplements that contain polyvalent cations by at least 4 hours. Consider therapy modification

Dolutegravir: Magnesium Salts may decrease the serum concentration of Dolutegravir. Management: Administer dolutegravir at least 2 hours before or 6 hours after oral magnesium salts. Consider therapy modification

Doxercalciferol: May enhance the hypermagnesemic effect of Magnesium Salts. Management: Consider using a non-magnesium-containing antacid or phosphate-binding product in patients also receiving doxercalciferol. If magnesium-containing products must be used with doxercalciferol, serum magnesium concentrations should be monitored closely. Consider therapy modification

Eltrombopag: Magnesium Salts may decrease the serum concentration of Eltrombopag. Management: Administer eltrombopag at least 2 hours before or 4 hours after oral administration of any magnesium-containing product. Consider therapy modification

Gabapentin: Magnesium Salts may enhance the CNS depressant effect of Gabapentin. Specifically, high dose intravenous/epidural magnesium sulfate may enhance the CNS depressant effects of gabapentin. Magnesium Salts may decrease the serum concentration of Gabapentin. Management: Administer gabapentin at least 2 hours after oral magnesium salts administration. Monitor patients closely for evidence of reduced response to gabapentin therapy. Monitor for CNS depression if high dose IV/epidural magnesium sulfate is used. Consider therapy modification

Levothyroxine: Magnesium Salts may decrease the serum concentration of Levothyroxine. Management: Separate administration of oral levothyroxine and oral magnesium salts by at least 4 hours. Consider therapy modification

Multivitamins/Fluoride (with ADE): Magnesium Salts may decrease the serum concentration of Multivitamins/Fluoride (with ADE). Specifically, magnesium salts may decrease fluoride absorption. Management: To avoid this potential interaction separate the administration of magnesium salts from administration of a fluoride-containing product by at least 1 hour. Consider therapy modification

Mycophenolate: Magnesium Salts may decrease the serum concentration of Mycophenolate. Management: Separate doses of mycophenolate and oral magnesium salts. Monitor for reduced effects of mycophenolate if taken concomitant with oral magnesium salts. Consider therapy modification

Neuromuscular-Blocking Agents: Magnesium Salts may enhance the neuromuscular-blocking effect of Neuromuscular-Blocking Agents. Monitor therapy

Phosphate Supplements: Magnesium Salts may decrease the serum concentration of Phosphate Supplements. Management: This applies only to oral phosphate and magnesium administration. Administer oral phosphate supplements at least 1 hour before, or 2 hours after, oral magnesium salt administration. Exceptions: Sodium Glycerophosphate Pentahydrate. Consider therapy modification

Quinolone Antibiotics: Magnesium Salts may decrease the serum concentration of Quinolone Antibiotics. Management: Administer oral quinolones several hours before (4 h for moxi- and sparfloxacin, 2 h for others) or after (8 h for moxi-, 6 h for cipro/dela-, 4 h for lome-, 3 h for gemi-, and 2 h for levo-, nor-, or ofloxacin or nalidixic acid) oral magnesium salts. Exceptions: LevoFLOXacin (Oral Inhalation). Consider therapy modification

Raltegravir: Magnesium Salts may decrease the serum concentration of Raltegravir. Management: Avoid the use of oral / enteral magnesium salts with raltegravir. No dose separation schedule has been established that adequately reduces the magnitude of interaction. Avoid combination

Tetracycline Derivatives: Magnesium Salts may decrease the absorption of Tetracycline Derivatives. Only applicable to oral preparations of each agent. Consider therapy modification

Trientine: May decrease the serum concentration of Magnesium Salts. Magnesium Salts may decrease the serum concentration of Trientine. Consider therapy modification

Adverse Reactions

Frequency not defined: Gastrointestinal: Diarrhea (excessive oral doses)

Warnings/Precautions

Disease-related concerns:

• Neuromuscular disease: Use with extreme caution in patients with myasthenia gravis or other neuromuscular disease.

• Renal impairment: Use with caution in patients with renal impairment; accumulation of magnesium may lead to magnesium intoxication.

Special populations:

• Obstetrics: Vigilant monitoring and safe administration techniques (ISMP Medication Safety Alert, 2005) recommended to avoid potential for errors resulting in toxicity. Monitor patient and fetal status, and serum magnesium levels closely.

Dosage form specific issues:

• Aluminum: The parenteral product may contain aluminum; toxic aluminum concentrations may be seen with high doses, prolonged use, or renal dysfunction. Premature neonates are at higher risk due to immature renal function and aluminum intake from other parenteral sources. Parenteral aluminum exposure of >4 to 5 mcg/kg/day is associated with CNS and bone toxicity; tissue loading may occur at lower doses (Federal Register, 2002). See manufacturer’s labeling.

• Benzyl alcohol and derivatives: Some dosage forms may contain benzyl alcohol; large amounts of benzyl alcohol (≥99 mg/kg/day) have been associated with a potentially fatal toxicity (“gasping syndrome”) in neonates; the “gasping syndrome” consists of metabolic acidosis, respiratory distress, gasping respirations, CNS dysfunction (including convulsions, intracranial hemorrhage), hypotension, and cardiovascular collapse (AAP ["Inactive" 1997]; CDC, 1982); some data suggests that benzoate displaces bilirubin from protein binding sites (Ahlfors, 2001); avoid or use dosage forms containing benzyl alcohol with caution in neonates. See manufacturer’s labeling.

Other warnings/precautions:

• Electrolyte abnormalities: Concurrent hypokalemia or hypocalcemia can accompany a magnesium deficit. Hypomagnesemia is associated with hypokalemia and requires correction in order to normalize potassium.

• Parenteral administration: Monitor serum magnesium level, respiratory rate, blood pressure, deep tendon reflex, and renal function when administered parenterally, particularly with repeated dosing; magnesium toxicity can lead to fatal cardiovascular arrest and/or respiratory paralysis.

Monitoring Parameters

IV: Rapid administration: ECG monitoring, vital signs, deep tendon reflexes; magnesium, calcium, and potassium levels; renal function during administration

Oral: Renal function; magnesium levels; bowel movements

Pregnancy Risk Factor

C

Pregnancy Considerations

Animal reproduction studies have not been conducted. Magnesium crosses the placenta; serum levels in the fetus correlate with those in the mother (Idama, 1998; Osada, 2002).

Patient Education

• Discuss specific use of drug and side effects with patient as it relates to treatment. (HCAHPS: During this hospital stay, were you given any medicine that you had not taken before? Before giving you any new medicine, how often did hospital staff tell you what the medicine was for? How often did hospital staff describe possible side effects in a way you could understand?)

• Have patient report immediately to prescriber flushing, sweating a lot, dizziness, passing out, loss of strength and energy, shortness of breath, sensation of cold, severe nausea, severe vomiting, or severe diarrhea (HCAHPS).

• Educate patient about signs of a significant reaction (eg, wheezing; chest tightness; fever; itching; bad cough; blue skin color; seizures; or swelling of face, lips, tongue, or throat). Note: This is not a comprehensive list of all side effects. Patient should consult prescriber for additional questions.

Intended Use and Disclaimer: Should not be printed and given to patients. This information is intended to serve as a concise initial reference for health care professionals to use when discussing medications with a patient. You must ultimately rely on your own discretion, experience, and judgment in diagnosing, treating, and advising patients.