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Antacids: Nursing Pharmacology



Mechanism of Action
Gastric acid-neutralizing agent; reacts with excess acid in the stomach, reducing acidity
Route of Administration
PO, enteral
Aluminum hydroxide 
(AlternaGEL, Amphojel, Nephrox)
GI disorders associated with hyperacidityUse with caution in clients with hypertension, heart failure, and low serum phosphate levels
Calcium carbonate 
(Dicarbosil, Rolaids, Titralac, Tums)
Should not be taken with milk products or vitamin D supplements
Calcium carbonate with magnesium hydroxide 
(Mi-Acid Double Strength, Mylanta Supreme, Rolaids, Fast Acting Mylanta)
Calcium component: Hypercalemia and hypercalciuria, severe renal disease, renal calculi, GI bleeding or obstruction and dehydration

Magnesium component: Abdominal pain, nausea & vomiting, diarrhea, fecal impaction, rectal bleeding, colostomy or ileostomy in place

Should not be taken with milk products or vitamin D supplements
(Lowsium, Ron-Acid)
Severe renal disease

Use cautiously in clients with mild renal impairment
Magnesium hydroxide 
(Milk of Magnesia, Pedia-Lax, Almacone)
Abdominal pain, nausea & vomiting, diarrhea, renal impairment, fecal impaction, rectal bleeding, colostomy or ileostomy in place
Magnesium trisilicate and aluminum hydroxide 
(Gaviscon Tablet)
Impaired kidney function, diarrhea, hypophosphatemia, hemorrhoids, intestinal blockage, constipation, aluminum poisoning, chronic diarrhea, chronic heart failure, severe renal impairment, visible water retention, decreased urine production, hypernatremia
Magnesium hydroxide and aluminum hydroxide 
(Mylanta, Mygel, DiGel, Gelusil, Rulox)
Use with caution in clients with hypertension, heart failure
Magnesium hydroxide, aluminum hydroxide, and simethicone
(Almacone, Gelusil, Mag-al Plus, Mi-Acid, Milantex)
GI disorders associated with hyperacidity; antiflatulentImpaired renal function, diarrhea, hypophosphatemia, henorrhoids, intestinal blockage, constipation, aluminum poisoning, chronic diarrhea
Sodium bicarbonate 
GI disorders associated with hyperacidityShould not be used in clients on a sodium-restricted diet
  • All antacids should be administered and taken on a regular schedule
  • Clients should be educated to chew antacids tablets well and follow them with water or milk, if not contraindicated
  • Antacids that come in liquid form need to be shaken before taken
  • If administering an antacid via nasogastric tube (NGT), be sure to flush with water following the medication
  • Use with caution in lactating women
  • Keep out of reach of children
  • Aluminum compounds: can reduce the effects of tetracyclines, warfarin sodium and digoxin
  • Magnesium compounds: magnesium hydroxide is also saline laxative, commonly causes diarrhea when used alone
  • Calcium compounds: can cause acid rebound
  • Sodium compounds: useful for treating acidosis and elevating urinary pH to promote excretion of certain drugs following overdose
High Yield Notes
1 pages

Antacids are acid reducing medications that directly lower the acidity of stomach contents. They are used to treat conditions like gastroesophageal reflux disorder, or GERD, and peptic ulcer disease, or (PUD).

When combined with antiflatulent medications like simethicone, they also help decrease gas production, which provides comfort and relief to clients experiencing gas or bloating. Antacids can be made up of aluminum, magnesium, calcium or sodium compounds.

Common antacid medications include: aluminum hydroxide, aluminum hydroxide and simethicone, magnesium hydroxide, magnesium hydroxide and aluminum hydroxide, magnesium trisilicate and aluminum hydroxide, magaldrate, calcium carbonate, calcium carbonate with magnesium hydroxide, and sodium bicarbonate.

Now when antacids are taken, the medication reacts with gastric acid and results in the production of neutral or low-acidity salts that increase the gastric pH. Additionally, the enzyme pepsin that normally helps digest protein is also inactivated.

The outcomes of these reactions are a decrease in gastric acidity, enhanced mucosal protection and a reduction of the symptoms associated with GI conditions such as GERD and PUD.

Antacids can cause several side effects If they are taken for an extended period of time, they may alter aluminum, calcium, sodium and phosphate levels.

Other general side effects of antacids include belching, constipation, flatulence, diarrhea and gastric distention.

Since all antacids increase gastric pH and can potentially bind with other drugs, absorption and effectiveness of medications taken along with antacids can be affected.

For example, they can increase oral absorption of medications that are weak bases, such as quinidine, an antiarrhythmic and anti-parasite medication; and decrease the oral absorption of medications that are weak acids, such as warfarin sodium.

Also, antacids can chelate, or bond, other medications in the GI tract, resulting in new complexes that are not absorbable.

This is especially common with medications such as tetracyclines, a class of antibiotics. So, spacing out antacids from other medications by 1-2 hours, or as prescribed, is important.

Depending on the medication’s compound, side effects can vary amongst different types of antacids.

For aluminum based antacids, constipation, hypophosphatemia, which can manifest as anorexia, malaise, tremors and muscle weakness; and aluminum toxicity with prolonged use can occur.

A common side effect of magnesium based antacids is diarrhea. However, when combined with an aluminum based compound, it is less likely to occur.

Calcium based antacids can cause hypercalcemia and metabolic alkalosis, and sodium bicarbonate antacids have the potential to worsen hypertension and the risk for heart failure, largely because of the sodium content it contains.

  1. "Pearson Reviews & Rationales: Comprehensive Review for NCLEX-RN, 3rd Edition" Pearson (2018)
  2. "Saunders Comprehensive Review for NCLEX-PN"  (1999)
  3. "Physiology, Pepsin"  (2021)