magnesium salts (oral)

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

Classifications ⬆ ⬇

Therapeutic Classification: mineral and electrolyte replacements/supplements, laxatives

Pharmacologic Classification: salines

Indications ⬆ ⬇

REMS

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.

Action ⬆ ⬇

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.

Therapeutic effects:

Replacement in deficiency states.
Evacuation of the colon.

Pharmacokinetics ⬆ ⬇

Absorption: Up to 30% may be absorbed orally.

Distribution: Widely distributed to tissues.

Metabolism/Excretion: Excreted primarily by the kidneys.

Half-Life: Unknown.

Time/Action Profile ⬆ ⬇

(laxative effect)

ROUTE	ONSET	PEAK	DURATION
PO	3–6 hr	unknown	unknown

Contraind./Precautions ⬆ ⬇

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.

Adv. Reactions/Side Effects ⬆ ⬇

Derm: flushing, sweating

GI: diarrhea

Interactions ⬆ ⬇

Drug-drug:

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

Route/Dosage ⬆ ⬇

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.

Availability ⬆ ⬇

Magnesium Chloride

Magnesium Citrate

Magnesium Gluconate

Magnesium Hydroxide

Magnesium Oxide

Sustained-release tablets: 535 mg (64 mg magnesium)OTC
Oral solution: 240-; 296-; and 300-mL bottles (77 mEq magnesium/100 mL)OTC
Tablets: 500 mgOTC
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
Tablets: 400 mg (241.3 mg magnesium)OTC

Assessment ⬆ ⬇

Laxative: Assess patient for abdominal distention, presence of bowel sounds, and usual pattern of bowel function.
- Assess color, consistency, and amount of stool produced.
Antacid: Assess for heartburn and indigestion as well as location, duration, character, and precipitating factors of gastric pain.

Implementation ⬆ ⬇

PO: To prevent tablets entering small intestine in undissolved form, they must be chewed thoroughly before swallowing. Follow with ½ glass of water.
- Magnesium citrate: Refrigerate solutions to ensure they retain potency and palatability. May be served over ice. Magnesium citrate in an open container will lose carbonation upon standing; this will not affect potency but may reduce palatability.
- Magnesium hydroxide: Shake solution well before administration.
Antacid: Administer 1–3 hr after meals and at bedtime.
- Powder and liquid forms are considered more effective than tablets.
Laxative: Administer on empty stomach for more rapid results. Follow all oral laxative doses with a full glass of liquid to prevent dehydration and for faster effect. Do not administer at bedtime or late in the day.

Patient/Family Teaching ⬆ ⬇

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.

Evaluation/Desired Outcomes ⬆ ⬇

Relief of gastric pain and irritation.
Passage of a soft, formed bowel movement, usually within 3–6 hr.
Prevention and treatment of magnesium deficiency.

US Brand Names ⬆

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

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

magnesium gluconate (5.4% Mg; 4.4 mEq/g):

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

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Pronunciation ⬇