MAGNESIUM HYDROXIDE  (mag-nes'i-um)  Magnesia, Magnesia Magma, Milk of Magnesia, M.O.M. Classifications: saline cathartic; antacid; Therapeutic: laxative; antacid Pregnancy Category: B
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Availability
311 mg tablets; 400 mg/5 mL, 800 mg/5 mL suspension
Action
Aqueous suspension of magnesium hydroxide with rapid and long-acting neutralizing action. May cause slight acid rebound.
Causes osmotic retention of fluid, which distends colon, resulting in mechanical stimulation of peristaltic activity.
Therapeutic Effect
Acts as antacid in low doses and as mild saline laxative at higher doses.
Uses
Short-term treatment of occasional constipation, for relief of GI symptoms associated with hyperacidity, and as adjunct
in treatment of peptic ulcer. Also has been used in treatment of poisoning by mineral acids and arsenic, and as mouthwash
to neutralize acidity.
Contraindications
Abdominal pain, nausea, vomiting, chronic diarrhea, severe kidney dysfunction, fecal impaction, intestinal obstruction or
perforation, rectal bleeding, colostomy, ileostomy, children <2 y is not established.
Cautious Use
Older adults, renal impairment, renal disease; pregnancy category B, lactation.
Route & Dosage
Laxative Adult: PO 2.44.8 g (3060 mL)/d in 1 or more divided doses Child: PO 25 y, 0.41.2 g (515 mL)/d in 1 or more divided doses; 611 y, 1.22.4 g (1530 mL)/d in 1 or more divided doses
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Administration
Oral
- Shake bottle well before pouring to assure mixing of suspension.
- Follow drug with at least a full glass of water to enhance drug action for laxative effect. Administer in the morning or
at bedtime. Most effective when taken on an empty stomach.
- Store at 15°30° C (59°86° F) in tightly covered container. Slowly absorbs carbon dioxide
on exposure to air. Avoid freezing.
Adverse Effects (≥1%)
GI: Nausea, vomiting, abdominal cramps,
diarrhea. Urogenital: Alkalinization of urine.
Body as a Whole: Weakness, lethargy, mental
depression, hyporeflexia, dehydration,
coma. Metabolic: Electrolyte imbalance with prolonged use.
CV: Hypotension, bradycardia,
complete heart block and
other ECG abnormalities. Respiratory: Respiratory depression.
Interactions
Drug: Milk of Magnesia decreases absorption of
chlordiazepoxide, dicumarol, digoxin, isoniazid, quinolones,
tetracyclines.
Pharmacokinetics
Absorption: 1530% of magnesium is absorbed.
Onset: 36 h.
Distribution: Small amounts distributed in saliva and breast milk.
Elimination: In feces; some renal excretion.
Nursing Implications
Assessment & Drug Effects
- Evaluate the patient's continued need for drug. Prolonged and frequent use of laxative doses may lead to dependence. Additionally,
even therapeutic doses can raise urinary pH and thereby predispose susceptible patients to urinary infection and urolithiasis.
- Lab tests: Monitor serum magnesium with signs of hypermagnesemia such as bradycardia (see Appendix F), especially with frequent
use or any degree of renal impairment.
Patient & Family Education
- Investigate the cause of persistent or recurrent constipation or gastric distress with physician.