Does Malox (aluminum hydroxide) cause constipation?

Does Maalox Cause Constipation?

Yes, Maalox (aluminum hydroxide with magnesium hydroxide) can cause constipation, primarily due to its aluminum hydroxide component, as explicitly stated in the FDA drug label. 1

Mechanism and Evidence

The FDA drug label for aluminum hydroxide clearly warns: "When using this product you may get constipated." 1 This constipating effect is attributable specifically to the aluminum hydroxide component of Maalox, which is a well-recognized side effect of aluminum-containing antacids.

Why Aluminum Causes Constipation

• Aluminum-containing antacids like aluminum hydroxide have a constipating effect on the gastrointestinal tract 1
• This is in contrast to magnesium-containing antacids, which tend to cause diarrhea 2
• Maalox contains both aluminum hydroxide and magnesium hydroxide, with the combination designed to balance these opposing effects 3

Clinical Considerations

Tolerability in Studies

• In a clinical study of 15 healthy volunteers receiving Maalox 70 (4 x 10 ml/day), the drug was subjectively well-tolerated and "the stool quality and quantity of the subjects did not change" 3
• However, this does not negate the FDA warning, as individual responses vary and the constipating effect may be more pronounced in certain patients 1

Special Populations at Risk

Patients with chronic kidney disease should be particularly cautious:

• Aluminum accumulation occurs with regular use of aluminum-containing antacids, especially in patients with renal insufficiency 2
• Saline laxatives containing magnesium hydroxide should be used cautiously in renal impairment due to risk of hypermagnesemia 2

Elderly patients require special attention:

• Elderly individuals are at higher risk for constipation complications 2
• Non-ambulatory patients with low fluid intake should avoid bulk agents due to increased risk of mechanical obstruction 2

Management if Constipation Develops

If constipation occurs while taking Maalox:

• Stop use and consult a physician if symptoms persist beyond 2 weeks 1
• Consider switching to alternative antacids without aluminum 2
• Implement standard constipation management strategies:
  • Increase fluid intake and physical activity when appropriate 2, 4
  • Consider osmotic laxatives such as polyethylene glycol (PEG 17g daily) 2
  • Use stimulant laxatives (bisacodyl or senna) for short-term relief or rescue therapy 2

Important Drug Interactions

Antacids may interact with certain prescription drugs 1, including:

• Fluoroquinolone antibiotics: Maalox substantially decreases rufloxacin absorption when taken within 5 minutes (reducing bioavailability to 64% of control) 5
• Spacing antacid administration 4 hours after medications can minimize this interaction 5