31.1 Antacids

Sodium Bicarbonate

Sodium bicarbonate is an alkaline substance that neutralizes excess stomach acid. When sodium bicarbonate comes in contact with stomach acid, it reacts with the acid to form water, carbon dioxide, and sodium chloride, also known as common table salt. It is commonly used orally as a tablet or powder to alleviate the burning sensation and discomfort caused by indigestion or heartburn. Because it contains sodium, it may not be suitable for individuals on sodium-restricted diets or those with conditions that cause fluid retention, such as heart failure and chronic kidney disease. See drug emphasis Table 31.1 for dosing information.

Calcium Carbonate

Calcium carbonate is a fast-acting oral antacid that efficiently neutralizes gastric acids, offering relief from heartburn and associated symptoms. It also serves as a calcium supplement, beneficial for conditions such as osteoporosis and hypocalcemia. Calcium carbonate also aids peristalsis in the esophagus, reducing acid reflux by pushing gastric acid back into the stomach (Salisbury & Terrell, 2022). It effectively treats hyperacidity symptoms linked to various conditions, including indigestion, esophagitis, and hiatal hernia. In clients with chronic renal failure and hyperphosphatemia, calcium carbonate helps manage excess phosphorus due to kidney insufficiency.

Calcium carbonate is administered by mouth as a sustained-released capsule, chewable tablet, or a powder that can be mixed in water. Chewable tablets must be chewed thoroughly before swallowing. Sustained-released capsules should be swallowed whole and never chewed. When taken as an antacid, calcium carbonate is administered 1 hour after meals and at bedtime. Calcium supplements should always be taken with vitamin D, as vitamin D is essential for efficient absorption of calcium (Rosen, 2023). See drug prototype Table 31.2 for additional information.

Aluminum Hydroxide

Aluminum hydroxide is a formulation of aluminum hydrochloride and water. It functions as an antacid by neutralizing excess stomach acid, primarily hydrochloric acid. It raises the pH (a measure of acidity) of gastric and esophageal secretions to reduce acid by making the secretions more alkaline.

Aluminum hydroxide is used to relieve intermittent hyperacidity symptoms from gastritis, GERD, and hiatal hernia. It may also be used as an adjunct medication for ulcers (gastric and duodenal) due to its alkalization properties. It is often used in combination with other antacids. These combination antacids provide both acid-neutralizing properties and relief from potential constipation. See drug emphasis Table 31.1 for dosing information.

Magnesium Hydroxide

Magnesium hydroxide is a commonly used active ingredient in antacid medications. Its role involves the neutralization of stomach acid. Similar to the other antacids mentioned in this chapter, it achieves this by leveraging its alkaline properties to counteract excessive stomach acidity. Magnesium hydroxide is often combined with aluminum hydroxide, and sometimes simethicone, to provide relief from heartburn, indigestion, and upset stomach with gas and bloating.

Magnesium hydroxide also has a laxative effect by causing osmotic fluid retention in the colon. This results in colon distention that stimulates peristalsis. When taken in larger quantities or more frequently than recommended, magnesium hydroxide can act as a mild laxative, potentially resulting in diarrhea. The magnesium in magnesium hydroxide can impact phosphorous digestion. Magnesium and phosphorus engage in a competitive absorption process within the small intestine. When there is a substantial disparity in the dietary intake of these minerals, one may hinder the absorption of the other, potentially leading to a deficiency in the inhibited mineral.

Magnesium hydroxide is an aqueous suspension that needs to be shaken well before use to mix the suspension. Magnesium hydroxide is most effective when administered on an empty stomach. It is best administered in the morning or at bedtime. Doses should be followed by at least 8 ounces of water if used as a laxative. The medication should be stored at 15°–30°C (59°–86°F). See drug emphasis Table 31.1 for dosing information.

Table 31.1 lists the common antacids and typical routes and dosing for adult clients.

Adverse Effects and Contraindications

Typical adverse effects of antacids include constipation (particularly those containing aluminum or calcium when used in large amounts or for extended periods of time), diarrhea (specifically antacids containing magnesium, which have a laxative effect), rebound hyperacidity (when the antacid wears off and the stomach produces additional acid), kidney stones (particularly from antacids containing calcium, as some kidney stones are caused by calcium oxalate), and gas and bloating.

When used excessively or for prolonged periods of time, antacids can potentially lead to electrolyte imbalances. The specific electrolyte imbalance that can result from antacid use depends on the types of minerals they contain. Electrolyte imbalances associated with antacids include:

• Hypercalcemia: Antacids that contain calcium, such as calcium carbonate, can lead to elevated calcium levels in the bloodstream. Symptoms may include excessive thirst, frequent urination, abdominal pain, nausea, vomiting, constipation, and fatigue.
• Hypermagnesemia: Antacids containing magnesium, like magnesium hydroxide, can cause elevated magnesium levels. Symptoms may include muscle weakness, nausea, vomiting, diarrhea, low blood pressure, and in severe cases, cardiac arrhythmias and respiratory distress.
• Hypernatremia: Antacids containing sodium, like sodium bicarbonate, can cause elevated sodium levels. Symptoms may include excessive thirst, dry mouth, confusion, restlessness, edema, or muscle twitching.
• Hypophosphatemia: Although less common, antacids (particularly magnesium hydroxide) can potentially interfere with the absorption of phosphate in the digestive tract, leading to low phosphorous levels in the blood. Symptoms may include muscle weakness, bone pain, confusion, and fatigue.

Contraindications to antacids include hypersensitivity to the antacid or any of its components. Individuals with kidney disease or heart failure should use antacids containing magnesium, aluminum, or sodium cautiously, as these may impact kidney function.

Table 31.2 is a drug prototype table for antacids featuring calcium carbonate. It lists drug class, mechanism of action, adult dosage, indications, therapeutic effects, drug and food interactions, adverse effects, and contraindications.

Nursing Implications

The nurse should do the following for clients who are taking antacids:

• Prior to administering, assess the client’s medical history, current drug list, and allergies.
• Educate the client regarding antacid effects, such as constipation, gas, and diarrhea.
• Monitor fluid intake and urine output (I&Os) for urinary retention and edema with sodium bicarbonate.
• Provide the client with teaching regarding the drug and when to call the health care provider. See below for additional client teaching guidelines.