Antacids (Monograph)

Brand names: Alamag, Alamag Plus, Alka-Mints, Alka-Seltzer Gold Effervescent Antacid, Almacone, ... show all 56 brands
Drug class: Antacids and Adsorbents
- Antiulcer Agents
ATC class: A02A
VA class: GA209
CAS number: 53547-27-6

Introduction

Inorganic salts that partially neutralize gastric hydrochloric acid.

Uses for Antacids

Peptic Ulcers

Adjunct to other drugs (e.g., anti-infectives, histamine H₂-receptor antagonists, proton-pump inhibitors) for the relief of peptic ulcer pain and to promote the healing of peptic ulcers.

Because of the inconvenience of the regimens needed to promote ulcer healing, high recurrence rate, ineffectiveness in eradicating Helicobacter pylori, palatability issues, and adverse effects, antacids rarely are used alone any longer for the treatment of peptic ulcer disease. Instead, antacids currently are used principally as an adjunct to other antiulcer regimens for as-needed (prn) relief of peptic ulcer pain.

Acid Indigestion

Self-medication for the relief of acid indigestion (dyspepsia), heartburn, and sour stomach and/or bloating (commonly referred as gas).

Gastroesophageal Reflux Disease (GERD)

Self-medication for the relief of mild forms of GERD (e.g., symptoms induced by a heartburn-inducing meal).

Antacids generally provide more rapid but less prolonged relief of GERD symptoms compared with histamine H₂-receptor antagonists, and combined therapy generally is more effective than either class of drugs alone.

Consult a clinician if symptoms persist or warning signs of more severe GERD develop (e.g., dysphagia, bleeding, weight loss, choking [acid-induced cough, shortness of breath, and/or hoarseness], chest pain).

Other agents (e.g., histamine H₂-receptor antagonists, proton-pump inhibitors) preferred by American College of Gastroenterology (ACG) and American Gastroenterological Association (AGA) for management of more severe forms of GERD.

Have been used for self-medication for the relief of breakthrough symptoms in patients receiving proton-pump inhibitors.

Hyperphosphatemia

Aluminum-containing antacids (except aluminum phosphate): Management of hyperphosphatemia or prevention of recurrent phosphatic renal calculi (in conjunction with a low phosphate diet).

Aluminum carbonate generally preferred to aluminum hydroxide for this use.

Calcium Replacement

Calcium carbonate is used for calcium supplementation.

Stress Ulceration and GI Bleeding

Has been used for prevention of stress ulceration^{† [off-label]} and GI bleeding^{† [off-label]}.

Gastric Acid Aspiration

Has been used for prevention of gastric acid aspiration^{† [off-label]} in patients undergoing cesarean section or emergency surgery; generally has been replaced by histamine H₂-receptor antagonist or citrate solution.

Antacids Dosage and Administration

Administration

Oral Administration

Administer orally.

Oral suspensions more rapidly and effectively solubilized than powders or tablets; reserve oral tablets for chronic use in patients who refuse oral suspensions because of inconvenience or unpalatable taste. Rapidly disintegrating tablets may be a suitable alternative in some patients.

Chew tablets, including rapidly dissolving tablets, thoroughly before swallowing.

Dosage

Available as various inorganic salts (e.g., aluminum carbonate, aluminum hydroxide, calcium carbonate, magnesium hydroxide, magnesium oxide, sodium bicarbonate); dosage is expressed in terms of mEq of acid neutralizing capacity.

Dose and frequency of administration depend on the acid secretory rate of the stomach, gastric emptying time, and the disorder being treated.

Adults

Peptic Ulcers

For peptic ulcer disease, dosages of antacids are empirical and various antacid dosages have been used.

Adjunctive Therapy

Oral

For supplemental ulcer pain relief, 40–80 mEq acid neutralizing capacity on an as-needed (prn) basis.

Treatment

Oral

Other therapies currently are preferred for treatment of active peptic ulcers. (See Peptic Ulcers under Uses.)

If antacids are used for the treatment of peptic ulcers, usual high-dose regimens for ulcer healing employ 80–160 mEq acid neutralizing capacity, given 1 and 3 hours after meals and at bedtime.

Additional doses of antacids may be administered to relieve ulcer pain that occurs between regularly scheduled doses.

In patients with duodenal ulcers, antacids usually are given for 4–6 weeks. If symptoms of duodenal ulcer recur, antacids can be administered 1 and 3 hours after meals and at bedtime for 1 week and, if pain is relieved, less frequently for an additional 1–2 weeks.

In patients with gastric ulcers, antacids are administered until healing is complete.

Gastroesophageal Reflux Disease (GERD)

For GERD, dosages of antacids are empirical and various antacid dosages have been used.

Oral

For relief of heartburn, one recommended regimen employs 40–80 mEq acid neutralizing capacity on an as-needed (prn) basis intially. If necessary, dosage can be titrated to a regularly scheduled basis such as 40–80 mEq acid neutralizing capacity given after meals and at bedtime.

Hyperphosphatemia

Oral

In conjunction with dietary phosphate restriction in the management of hyperphosphatemia, 30–40 mL of aluminum hydroxide or aluminum carbonate suspension is administered 3 or 4 times daily.

Stress Ulceration and GI Bleeding

Oral

In the management of stress ulceration^{† [off-label]} and GI bleeding^{† [off-label]}, antacids are usually administered every hour, and the antacid dosage should be titrated to maintain the nasogastric aspirate above pH 3.5.

For severe symptoms, antacid suspensions may be diluted with water or milk and given by continuous intragastric infusion.

Gastric Acid Aspiration

Oral

To reduce the risk of anesthesia-induced gastric acid aspiration, an antacid suspension has been given 30 minutes before anesthesia.

Prescribing Limits

Adults

GERD

Oral

Do not exceed 500–600 mEq acid neutralizing capacity daily or regularly scheduled (versus as-needed; prn) therapy for longer than 2 weeks continuously.

Sodium Bicarbonate

Maximum daily dosage of sodium or bicarbonate is 200 mEq in patients <60 years of age and 100 mEq in patients >60 years of age. Contraindicated for prolonged therapy because it may cause metabolic alkalosis or sodium overload.

Cautions for Antacids

Contraindications

Sodium bicarbonate is contraindicated and use of other sodium-containing antacids should be restricted in patients on low-sodium diets and in those with CHF, renal failure, edema, or cirrhosis.

Warnings/Precautions

Warnings

Phenylketonuria

Some antacids may contain aspartame (e.g., NutraSweet), which is metabolized in the GI tract to phenylalanine following oral administration.

Sensitivity Reactions

Tartrazine Sensitivity

Some antacid formulations contain the dye tartrazine (FD&C yellow No. 5), which may cause allergic-type reactions (bronchial asthma in susceptible individuals) in certain susceptible individuals (e.g., patients who are sensitive to aspirin).

General Precautions

Aluminum Antacids

Risk of hypophosphatemia with prolonged administration or large doses, particularly in patients with inadequate dietary intake of phosphorus.

Monitor serum phosphate concentrations at monthly or bimonthly intervals in patients on maintenance hemodialysis who are receiving chronic aluminum antacid therapy.

Calcium Carbonate

May cause gastric hypersecretion and acid rebound.

May cause the milk-alkali syndrome (characterized by hypercalcemia, metabolic alkalosis and, rarely, renal insufficiency).

Monitor serum calcium concentrations weekly and whenever manifestations of hypercalcemia occur in patients receiving large doses of calcium carbonate.

Magnesium Antacids

Commonly cause a laxative effect, and frequent administration of these antacids alone often cannot be tolerated; repeated doses cause diarrhea which may cause fluid and electrolyte imbalances.

Sodium Bicarbonate

May cause metabolic alkalosis when given in large doses.

Medication Errors

Serious medication errors have been reported to FDA in which consumers used Maalox Total Relief (bismuth subsalicylate) when they intended to use traditional Maalox liquid antacid products containing aluminum hydroxide, magnesium hydroxide, and simethicone (e.g., Maalox Advanced Regular Strength, Maalox Advanced Maximum Strength). Because of the potential for serious adverse effects associated with accidental use of bismuth subsalicylate (which is chemically related to aspirin), the manufacturer of Maalox Total Relief initially agreed to change the trade name of the product to one that did not include “Maalox”; however, the manufacturer instead discontinued the bismuth subsalicylate preparation in the summer of 2010.

Specific Populations

Renal Impairment

Aluminum Antacids: Long-term administration in patients with renal failure or chronic renal failure may result in hyperaluminemia since small amounts of aluminum are absorbed from the GI tract and excretion of aluminum is decreased in patients with renal failure. Aluminum accumulation in the CNS may be the cause of dialysis encephalopathy, while aluminum accumulation in the bones may result in or worsen dialysis osteomalacia.

Calcium Carbonate: Patients with renal impairment or dehydration and electrolyte imbalance are predisposed to developing the milk-alkali syndrome. Hypercalcemia risk in chronic hemodialysis patients.

Magnesium Antacids: In patients with severe renal impairment, hypermagnesemia characterized by hypotension, nausea, vomiting, ECG changes, respiratory or mental depression, and coma. Do not administer in patients with renal failure, and antacids containing more than 50 mEq of magnesium in the recommended daily dosage should be used cautiously and only under the supervision of a clinician who should monitor electrolytes in patients with renal disease.

Sodium Bicarbonate: May cause metabolic alkalosis in patients with renal insufficiency.

Common Adverse Effects

With prolonged administration, constipation (e.g., aluminum salts, calcium carbonate), diarrhea (e.g., magnesium salts), gastric distension/flatulence (e.g., sodium bicarbonate), and gastric hypersecretion/acid rebound (e.g., calcium carbonate).

Drug Interactions

All antacids potentially may increase or decrease the rate and/or extent of absorption of concomitantly administered oral drugs by changing GI transit time or by binding or chelating the drug. In vitro studies indicate that magnesium hydroxide or trisilicate has the greatest potential for drug binding and aluminum hydroxide and calcium carbonate are intermediate.

Specific Drugs and Food

Drug	Interaction	Comments
Aspirin	Pharmacokinetic (increased absorption of buffered or enteric-coated aspirin or decreased blood salicylate concentrations) interactions
Chlordiazepoxide	Possible decreased chlordiazepoxide absorption with aluminum hydroxide and magnesium preparations
Diazepam	Possible increased diazepam absorption with aluminum hydroxide
Digoxin	Possible decreased digoxin absorption	Space doses of the drugs as far apart as possible
Indomethacin	Possible decreased indomethacin absorption	Space doses of the drugs as far apart as possible
Iron salts	Possible decreased absorption of iron salts	Space doses of the drugs as far apart as possible
Isoniazid	Possible decreased isoniazid absorption with aluminum hydroxide	Administer isoniazid at least 1 hour before aluminum-containing antacids
Milk or other calcium-containing foods	Possible milk-alkali syndrome with chronic administration of bicarbonate and milk or calcium
Naproxen	Possible increased naproxen absorption with sodium bicarbonate Possible decreased naproxen absorption with magnesium oxide or aluminum hydroxide
Pseudoephedrine	Possible increased pseudoephedrine absorption with aluminum hydroxide
Tetracyclines	Possible decreased tetracycline absorption	Allow 1–2 hours to elapse between doses of antacids and tetracyclines

Actions

Mechanism of action in the treatment of peptic ulcers is based on ability of antacids to react with hydrochloric acid and thus increase gastric pH.
With usual doses, antacids generally do not increase and maintain gastric pH above 4–5.
Antacids, in decreasing order of their ability to neutralize a given amount of acid, are calcium carbonate, sodium bicarbonate, magnesium salts, and aluminum salts.
Aluminum-containing antacids (except aluminum phosphate) combine with dietary phosphate in the intestine forming insoluble, nonabsorbable aluminum phosphate which is excreted in the feces. If phosphate intake is limited and renal function is normal, aluminum antacids (except aluminum phosphate) decrease phosphate absorption and hypophosphatemia and hypophosphaturia occur.
Magnesium-containing antacids have a laxative action.

Advice to Patients

Advise patients to consult a clinician if ulcer pain worsens or is not relieved after the first week of therapy.
Importance of consulting a clinician if GERD symptoms persist or warning signs of more severe GERD develop (e.g., dysphagia, bleeding, weight loss, choking [acid-induced cough, shortness of breath, and/or hoarseness], chest pain).
Importance of women informing their clinician if they are or plan to become pregnant or plan to breast-feed.
Importance of informing clinicians of existing or contemplated concomitant therapy, including prescription and OTC drugs, as well as concomitant illnesses.
Importance of informing patients of other important precautionary information. (See Cautions.)

Preparations

Excipients in commercially available drug preparations may have clinically important effects in some individuals; consult specific product labeling for details.

Please refer to the ASHP Drug Shortages Resource Center for information on shortages of one or more of these preparations.

Aluminum Carbonate, Basic
Routes	Dosage Forms	Strengths	Brand Names	Manufacturer
Oral	Capsules	equivalent to dried aluminum hydroxide gel 608 mg or aluminum hydroxide 500 mg	Basaljel	Wyeth
	Tablets	equivalent to dried aluminum hydroxide gel 608 mg or aluminum hydroxide 500 mg	Basaljel (scored)	Wyeth