magnesium hydroxide/aluminum hydroxide


mag-nee-zhum hye-drox-ide/ a-loo-mi-num hye-drox-ide

Trade Name(s)

  • Alamag
  • Diovol Plus Canadian Tradename
  • Maalox
  • Mylanta Ultimate
  • Rulox

Ther. Class.
antiulcer agents

Pharm. Class.


Useful in a variety of GI complaints, including:

  • Hyperacidity,
  • Indigestion,
  • GERD,
  • Heartburn.


  • Neutralize gastric acid following dissolution in gastric contents.
  • Inactivate pepsin if pH is raised to ≥4.

Therapeutic Effect(s):

Neutralization of gastric acid with healing of ulcers and decrease in associated pain.


Absorption: During routine use, antacids are nonabsorbable. With chronic use, 15–30% of magnesium and smaller amounts of aluminum may be absorbed.

Distribution: Small amounts absorbed are widely distributed, cross the placenta, and appear in breast milk. Aluminum concentrates in the CNS.

Metabolism and Excretion: Excreted by the kidneys.

Half-life: Unknown.


Aluminum POslightly delayed30 min30 min-1 hr (empty stomach); 3 hr (after meals)
Magnesium POslightly delayed30 min30 min-1 hr (empty stomach); 3 hr (after meals)


Contraindicated in:

  • Severe abdominal pain of unknown cause, especially if accompanied by fever
  • Renal failure (CrCl <30 mL/min)
  • Products containing tartrazine or sugar in patients with known intolerance.

Use Cautiously in:

  • Antacids containing magnesium in patients with any degree of renal insufficiency
  • ↓ bowel motility
  • Dehydration
  • Upper GI hemorrhage
  • Children <12 yr (safety not established).

Adverse Reactions/Side Effects

GI:  aluminum salts: constipation  magnesium salts: diarrhea

F and E:  magnesium salts: hypermagnesemia  aluminum salts: hypophosphatemia

* CAPITALS indicate life-threatening.
Underline indicate most frequent.



Absorption of  tetracyclines,  phenothiazines,  ketoconazole,  itraconazole,  iron salts,  fluoroquinolones, and  isoniazid  may be ↓ (separate by at least 2 hr).


PO (Adults and Children ≥12 yr): 5–30 mL or 1–2 tablets 1–3 hr after meals and at bedtime.

Availability (generic available)

Chewable Tablets: 300 mg aluminum hydroxide/150 mg magnesium hydroxideOTC

Suspension: 225 mg aluminum hydroxide/200 mg magnesium hydroxide/5 mLOTC, 500 mg aluminum hydroxide/500 mg magnesium hydroxide/5 mLOTC

In Combination with: simethiconeOTC . See combination drugs.


  • Antacid: Assess for heartburn and indigestion as well as location, duration, character, and precipitating factors of gastric pain.

Lab Test Considerations:

Monitor serum phosphate, potassium, and calcium levels periodically during chronic use. May cause ↑ serum calcium and ↓ serum phosphate concentrations.

Potential Diagnoses


  • Magnesium and aluminum are combined as antacids to balance the constipating effects of aluminum with the laxative effects of magnesium.
  • PO 

    To prevent tablets from entering small intestine in undissolved form, they must be chewed thoroughly before swallowing. Follow with at least ½ glass of water.

    • Shake suspensions well before administration.
    • For an antacid effect, administer 1–3 hr after meals and at bedtime.

Patient/Family Teaching

  • 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.
  • Advise patient not to take this medication within 2 hr of taking other medications.
  • Pedi:  Aluminum- or magnesium-containing medicines can cause serious side effects in children, especially when given to children with renal disease or dehydration. Advise parents or caregivers not to administer OTC antacids to children without consulting health care professional.

Evaluation/Desired Outcomes

Relief of gastric pain and irritation.

magnesium hydroxide/aluminum hydroxide is a sample topic from the Davis's Drug Guide.

To view other topics, please or .

Emergency Central is a collection of disease, drug, and test information including 5-Minute Emergency Medicine Consult, Davis’s Drug, McGraw-Hill Medical’s Diagnosaurus®, Pocket Guide to Diagnostic Tests, and MEDLINE Journals created for emergency medicine professionals. .