21.5
Acid Suppressive Drugs for Peptic Ulcer Disease: Antacids
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Q1: How do carbonate antacids neutralize gastric acid?
Carbonate antacids like sodium bicarbonate and calcium carbonate neutralize gastric acid by converting it into salt and water. This neutralization raises gastric pH from 1 to approximately 5, significantly reducing intragastric acidity and providing relief from ulcer-related discomfort in the mucosal layer.
Q2: What side effects result from excessive antacid doses?
Excessive antacid doses cause multiple problems: unreacted alkali absorption raises blood alkalinity, leading to metabolic alkalosis. Additionally, sodium increases fluid retention in hypertensive patients, while calcium triggers rebound acid secretion. CO2 accumulation from the neutralization reaction causes stomach distention and belching.
Q3: Why is magaldrate used instead of standard carbonate antacids?
Magaldrate, a hydroxymagnesium aluminate complex, converts into poorly absorbed magnesium and aluminum hydroxides in gastric acid. This transformation provides a sustained antacid effect while mitigating side effects like excessive CO2 production and metabolic alkalosis associated with carbonate antacids. It offers superior tolerability.
Q4: What factors determine antacid effectiveness?
Antacid efficiency depends on dissolution rate, water solubility, reaction speed with acid, and gastric emptying rate. Clearance is faster on an empty stomach, but when taken with food, their duration of action is prolonged, providing longer-lasting relief from gastric discomfort.
Q5: How does CO2 production affect antacid use?
The neutralization reaction between carbonate antacids and gastric acid produces carbon dioxide gas. CO2 accumulation causes stomach distention and belching, creating significant discomfort for patients. This is why magaldrate is preferred, as it generates poorly absorbed hydroxides instead, avoiding excessive gas production and related symptoms.
Q6: What is metabolic alkalosis and how do antacids cause it?
Metabolic alkalosis occurs when blood alkalinity increases abnormally. Excessive antacid doses lead to absorption of unreacted alkali, raising the blood's alkalinity and causing this condition. This is a significant concern with carbonate antacids, particularly at high doses, making careful dosing essential for patient safety.
Q7: How does food intake affect antacid duration?
Antacid clearance is faster when taken on an empty stomach, resulting in shorter action duration. However, when taken with food, their duration of action is prolonged, providing extended relief. This timing consideration is important for optimizing therapeutic benefit in managing acid suppressive drugs for peptic ulcer disease.