III. Contraindications

  1. Renal Failure
  2. Infants (relative contraindication)
    1. Higher risk for Hypermagnesemia

IV. Mechanism

  1. Magnesium salt Osmotic Laxative
  2. Poorly absorbed, hyperosmolar agent

V. Precautions

  1. Avoid longterm use due to Electrolyte loss risk
    1. These agents are typically used once as part of a bowel regimen

VI. Medications

  1. See Aluminum Hydroxide and Magnesium Hydroxide Antacid
  2. Magnesium Hydroxide Laxative concentrations
    1. Regular strength: 400 mg/5 ml
    2. Extra-Strength: 800 mg/5 ml
    3. Very High Concentration: 1200 mg/5 ml

VII. Dosing: Constipation

  1. See Aluminum Hydroxide and Magnesium Hydroxide Antacid
  2. General
    1. Onset 0.5 to 6 hours
    2. Recommended as a single bedtime dose
  3. Concentration: 400 mg/5 ml (regular strength)
    1. Adult (and age >12 years)
      1. Take 30 to 60 ml (2.4 to 4.8 g) orally divided once to twice for 1 day
    2. Child (age <12 years)
      1. Age <2 years: 0.5 ml/kg/day divided once to twice for 1 day (caution, risk of Hypermagnesemia)
      2. Age 2 to 5 years: 5 to 15 ml (0.4 to 1.2 g) divided once to twice for 1 day
      3. Age 6 to 12 years: 15 to 30 ml (1.2 to 2.4 g) divided once to twice for 1 day
  4. Concentration 800 mg/5 ml (extra strength)
    1. Adult: 15 to 30 ml orally divided once to twice for 1 day
  5. Concentration 1200 mg/5 ml (very high concentration)
    1. Adult: 10 to 20 ml orally divided once to twice for 1 day

VIII. Pharmacokinetics

  1. Rapid onset within 3 hours

IX. Adverse Effects

  1. Abdominal cramping (higher doses)
  2. Hypermagnesemia (in patients with Renal Failure, infants)

X. Safety

  1. Pregnancy Category B
  2. Unknown Safety in Lactation

XII. References

  1. (2023) Management of Constipation, Presc Lett, #390108
  2. Hamilton (2020) Tarascon Pocket Pharmacopoeia

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Related Studies

Cost: Medications

milk of magnesia (on 12/21/2022 at Medicaid.Gov Survey of pharmacy drug pricing)
MILK OF MAGNESIA SUSPENSION Generic OTC $0.01 per ml

Ontology: Magnesium Hydroxide (C0024476)

Definition (NCI) A solution of magnesium hydroxide with antacid and laxative properties. Milk of magnesium exerts its antacid activity in low doses such that all hydroxide ions that enter the stomach are used to neutralize stomach acid. This agent exerts its laxative effect in higher doses so that hydroxide ions are able to move from the stomach to the intestines where they attract and retain water, thereby increasing intestinal movement (peristalsis) and inducing the urge to defecate.
Definition (MSH) An inorganic compound that occurs in nature as the mineral brucite. It acts as an antacid with cathartic effects.
Concepts Pharmacologic Substance (T121) , Inorganic Chemical (T197)
MSH D008276
SnomedCT 387337001, 317584009, 25550008, 60468008
English Magnesium Hydrate, Hydroxide, Magnesium, Magnesium Hydroxide, Hydrate, Magnesium, Magnesium hydroxide (Mg(OH)2), magnesium hydroxide, Magnesium hydroxide [laxative], Magnesium hydrate, antacids magnesium OH, magnesium hydroxide (medication), MAGNESIUM HYDROXIDE, Magnesium Hydroxide [Chemical/Ingredient], magnesium hydrate, hydroxide laxative magnesium, hydroxide magnesium, Magnesium hydroxide [laxative] (product), Magnesium hydrate (substance), Magnesium hydroxide, Magnesium hydroxide (product), Magnesium hydroxide (substance), Magnesium hydroxide [laxative] (substance)
French Hydroxyde de magnésium
Swedish Magnesiumhydroxid
Czech hydroxid hořečnatý
Finnish Magnesiumhydroksidi
Russian MAGNIIA GIDROOKIS', BRUSIT, BRUTSIT, MAGNIIA GIDROKSID, БРУСИТ, БРУЦИТ, МАГНИЯ ГИДРОКСИД, МАГНИЯ ГИДРООКИСЬ
Japanese 水酸化マグネシウム, ブルーサイト
Italian Idrato di magnesio, Idrossido di magnesio
Polish Wodorotlenek magnezowy
Norwegian Magnesiumhydrat, Magnesiumhydroksid
Spanish hidróxido de magnesio (laxante), hidrato de magnesio (sustancia), hidróxido de magnesio (laxante) (producto), hidrato de magnesio, hidróxido de magnesio (producto), hidróxido de magnesio (sustancia), hidróxido de magnesio, Hidróxido de Magnesio
German Magnesiumhydroxid
Portuguese Hidróxido de Magnésio

Ontology: MILK OF MAGNESIA (C0591789)

Concepts Pharmacologic Substance (T121) , Inorganic Chemical (T197)
English MILK OF MAGNESIA, Milk of Magnesia, MILK OF MAGNESIA [VA Product], magnesia milk, milk of magnesia