Magaldrate (Hydroxymagnesium Aluminate)

 Action Neutralizes gastric acid, thereby increasing pH of stomach and duodenal bulb. Increases lower esophageal sphincter tone and inhibits smooth muscle contraction and gastric emptying.

 Indications Symptomatic relief of upset stomach associated with hyperacidity, including heartburn, gastroesophageal reflux, acid indigestion and sour stomach; relief of hyperacidity associated with peptic ulcer, gastritis, peptic esophagitis, gastric hyperacidity and hiatal hernia.

 Contraindications Severe renal dysfunction; hypophosphatemia; nausea; vomiting; severe abdominal pain; acute surgical abdomen; impaction; intestinal obstruction.

 Route/Dosage

ADULTS: PO 480–1080 mg qid prn or to aid in peptic ulcer healing or chronic reflux, give 1 hr and 3 hr after meals and at bedtime (7 doses/day). CHILDREN: PO 5–10 mg/dose q 3–6 hr or 1 hr and 3 hr after meals and at bedtime for peptic ulcer.

 Interactions

Iron: Decreased pharmacologic effect of iron. Ketoconazole: Decreased pharmacologic effect of ketoconazole. Nitrofurantoin: Decreased effects of nitrofurantoin. Penicillamine: Decreased pharmacologic effect of penicillamine. Quinidine: Increased pharmacologic effect of quinidine. Quinolones: Decreased pharmacologic effect of quinolones. Salicylates: Decreased pharmacologic effect of salicylates. Sodium polystyrene sulfonate: Concomitant use may cause metabolic alkalosis in patients with renal failure. Tetracyclines: Decreased pharmacologic effect of tetracyclines.

 Lab Test Interferences None well documented.

 Adverse Reactions

CNS: Neurotoxicity; encephalopathy. GI: Diarrhea; constipation; intestinal obstruction; rebound hyperacidity. META: Hypophosphatemia; hypermagnesemia. OTHER: Osteomalacia; bone pain; muscular weakness; malaise; decreased fluoride absorption; aluminum accumulation in serum, bone and CNS; milk-alkali syndrome.

 Precautions

Pregnancy: Pregnancy category undetermined. Lactation: Undetermined. GI hemorrhage: Use with care in patients with recent massive upper GI hemorrhage. Renal insufficiency: Use with caution in patients with renal impairment to avoid hypermagnesemia and toxicity.

 Administration/Storage

• Administer 1 hr and 3 hr after meals and at bedtime when ordered for treatment of ulcers or 4 times/day when ordered as necessary for relief of symptoms.
• If possible, administer antacid 1–2 hr before or after other medications.
• Shake suspension vigorously before pouring. Administer with sufficient water (approximately 4 oz) to ensure that drug reaches stomach.
• Chewable tablet should be chewed thoroughly before swallowing, followed by half a glass of water.
• Store at room temperature.

 Assessment/Interventions

• Obtain patient history, including drug history and any allergies.
• Assess for heartburn and indigestion, noting location, duration, character and precipitating factors of GI pain.
• Monitor serum magnesium level in patients with renal impairment.
• Monitor level of relief obtained by patient following medication.

 Patient/Family Education

• Instruct patient to take medication 1 and 3 hr after meals and at bedtime.
• Warn patient not to take other medications within 2 hr of antacid.
• Review proper use of suspension or tablet form.
• Advise patient to consult physician if problem recurs, if any symptoms that suggest bleeding occur (eg, black tarry stools) or if patient has taken antacids for more than 2 wk.