mag-NEE-zhum hye-DROX-ide/ a-LOO-mi-num hye-DROX-ide

Therapeutic Classification: antiulcer agents

Pharmacologic Classification: antacids

• 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.

• 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/Excretion: Excreted by the kidneys.

Half-life: Unknown.

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).

GI: aluminum salts: constipation.
magnesium salts: diarrhea.

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

Drug-Drug:

• 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.

(Generic available)

• Chewable Tablets: 300 mg aluminum hydroxide/150 mg magnesium hydroxide^OTC;
• Suspension: 225 mg aluminum hydroxide/200 mg magnesium hydroxide/5 mL^OTC; 500 mg aluminum hydroxide/500 mg magnesium hydroxide/5 mL^OTC;
• In combination with: simethicone^OTC. See Appendix [not included in this PDA edition].