• Treatment/prevention of hypomagnesemia.
• As a:
  • Laxative,
  • Bowel evacuant in preparation for surgical/radiographic procedures.
• Milk of magnesia has also been used as an antacid.

Contraindicated in:

• Hypermagnesemia
• Hypocalcemia
• Anuria
• Heart block
• OB: Unless used for preterm labor, use during active labor or within 2 hr of delivery may ↑ potential for magnesium toxicity in newborn.

Use Cautiously in:

• Renal impairment.

Derm: flushing, sweating.

GI: diarrhea.

Drug-Drug:

• Potentiates neuromuscular blocking agents.
• May ↓ absorption of fluoroquinolones, nitrofurantoin, and tetracyclines and penicillamine.

Magnesium Chloride

(generic available)

• Sustained-release tablets: 535 mg (64 mg magnesium)^OTC;

Magnesium Citrate

(generic available)

• Oral solution: 240-; 296-; and 300-mL bottles (77 mEq magnesium/100 mL)^OTC;

Magnesium Gluconate

(generic available)

• Tablets: 500 mg^OTC;

Magnesium Hydroxide

(generic available)

• Liquid: 400 mg/5 mL (164 mg magnesium/5 mL)^OTC;
• Concentrated liquid: 800 mg/5 mL (328 mg magnesium/5 mL)^OTC;
• Chewable tablets: 400 mg (173 mg magnesium)^OTC;

Magnesium Oxide

(generic available)

• Tablets: 400 mg (241.3 mg magnesium)^OTC;

Prevention of Deficiency (in mg of Magnesium)

• PO (Adults and Children >10 yr): Adolescent and adult men: 270–400 mg/day; Adolescent and adult women: 280–300 mg/day; Pregnant women: 320 mg/day; Breastfeeding women: 340–355 mg/day.
• PO (Children 7–10 yr): 170 mg/day.
• PO (Children 4–6 yr): 120 mg/day.
• PO (Children birth–3 yr): 40–80 mg/day.

Treatment of Deficiency (in mg of Magnesium)

• PO (Adults): 200–400 mg/day in 3–4 divided doses.
• PO (Children 6–11 yr): 3–6 mg/kg/day in 3–4 divided doses.

Laxative

• PO (Adults): Magnesium citrate: 240 mL; Magnesium hydroxide: 30–60 mL single or divided dose or 10–20 mL as concentrate.
• PO (Children 6–12 yr): Magnesium citrate: 100 mL; Magnesium hydroxide: 15–30 mL single or divided dose.
• PO (Children 2–5 yr): Magnesium hydroxide: 5–15 mL single or divided dose.

magnesium chloride (12% Mg; 9.8 mEq Mg/g): Slo-Mag

magnesium citrate (16.2% Mg; 4.4 mEq Mg/g): Citroma

magnesium hydroxide (41.7% Mg; 34.3 mEq Mg/g): Milk of Magnesia

magnesium oxide (60.3% Mg; 49.6 mEq Mg/g): Mag-Oxide

• Essential for the activity of many enzymes.
• Play an important role in neurotransmission and muscular excitability.
• Are osmotically active in GI tract, drawing water into the lumen and causing peristalsis.

• Replacement in deficiency states.
• Evacuation of the colon.

Therapeutic Classification: mineral and electrolyte replacements/supplements, laxatives

Pharmacologic Classification: salines

Absorption: Up to 30% may be absorbed orally.

Distribution: Widely distributed to tissues.

Metabolism/Excretion: Excreted primarily by the kidneys.

Half-life: Unknown.

(laxative effect)

• Advise patient not to take this medication within 2 hr of taking other medications, especially fluoroquinolones, nitrofurantoin, and tetracyclines.
• Antacids: Caution patient to consult health care professional before taking antacids for more than 2 wk if problem is recurring, if relief is not obtained, or if symptoms of gastric bleeding (black, tarry stools; coffee-ground emesis) occur.
• Laxatives: Advise patient that laxatives should be used only for short-term therapy. Long-term therapy may cause electrolyte imbalance and dependence.
  • Encourage patient to use other forms of bowel regulation, such as increasing bulk in the diet, fluid intake, and mobility. Normal bowel habits are individualized; frequency of bowel movement may vary from 3 times/day to 3 times/wk.
  • Advise patient to notify health care professional if unrelieved constipation, rectal bleeding, or symptoms of electrolyte imbalance (muscle cramps or pain, weakness, dizziness) occur.

magnesium chloride (12% Mg; 9.8 mEq Mg/g): mag-NEE-zhum KLOR-ide

magnesium citrate (16.2% Mg; 4.4 mEq Mg/g): mag-NEE-zhum SI-trate

Magnesium Gluconate (5.4% Mg; 4.4 mEq/g): mag-NEE-zhum GLOO-con-ate

magnesium hydroxide (41.7% Mg; 34.3 mEq Mg/g): mag-NEE-zhum hye-DROX-ide

magnesium oxide (60.3% Mg; 49.6 mEq Mg/g): mag-NEE-zhum OX-ide