Gastrointestinal Agents

dexeroso's version from 2017-06-18 12:03

Gastrointestinal Agents

Question Answer
Gastric Mucosal BarrierSpecial type of epithelial cells secrete mucus that has a high lipid, protein and carbohydrate content.
Acid Peptic DiseaseExcessive secretion of acid and pepsin or a weakened stomach mucosal defense is responsible for damage to the delicate mucosa and the lining of the stomach, esophagus and duodenum resulting in ulceration
– Antacids – H2-Receptor Antagonists – Proton-Pump InhibitorsDrugs that decrease acid


Question Answer
AntacidsAntacids neutralize acid and decrease pepsin activity.
Acid Neutralizing Capacity– number of milliequivalents of HCl required to maintain 1 ml of an antacid suspension at pH 3 for 2 hr in vitro.
• Soluble antacids such as NaHCO3 may cause systemic effects such as electrolyte imbalance and systemic alkalosis. • Hypercalcemia and Milk-Alkali Syndrome. • Rebound Hyperacidity. • Constipation; LaxationSide Effects of Antacids
Antacids• Sodium Bicarbonate • Basic Aluminum Carbonate Gel • Aluminum Hydroxide • Dihydroxyaluminum Sodium Carbonate • DihydroxyaluminumAcetate • Calcium Carbonate • Tribasic Calcium Phosphate
Sodium BicarbonateBaking Soda, Sodium Acid Carbonate
Basic Aluminum Carbonate GelBasalgel
Basic Aluminum Carbonate Gel Used for the treatment of gastric hyperacidity • Adjunct in the treatment of peptic ulcer • Since it is excreted as aluminum phosphate, this may cause phosphate urinary stones
Aluminum HydroxideColloidal Aluminum Hydroxide, Amphojel, Alternagel
Aluminum Hydroxide• Used in the management of peptic ulcer, gastritis and esophagitis. • Relatively weak antacid and does not elevate gastric pH sufficiently to inhibit pepsin activity • Not absorbed by the body.
hypophosphatemiaAluminum Hydroxide may cause ?
Dihydroxyaluminum Sodium Carbonate• Used in the treatment of dyspepsia and heartburn • Adjunct for the management of peptic ulcer, gastritis and esophagitis • A partial systemic antacid. • Has a rapid onset of action due to the sodium carbonate and a sustained but less intense antacid
Aluminum HydroxideDihydroxyaluminum Sodium Carbonate Action is due to(?)
Dihydroxyaluminum AminoacetateRapid onset of action due to the protonation of the amine group with a sustained buffering effect due to the two hydroxyls and glycine carboxyl group.• May cause constipation and hypophosphatemia.
Calcium Carbonate• Has rapid onset of action. • May cause constipation. • Indicated as a calcium supplement
Tribasic Calcium Phosphate• Antacid property may be due to H^+ accepting • Property of the phosphate anions or the production of OH- upon the hydrolysis of phosphate anions.
Calcium CarbonateTums/Precipitated Chalk

Protectives (Antacids)

Question Answer
– Combine fast- and slow-reacting antacids to obtain a product with a rapid onset and a relatively even, sustained action. – Lower the dose of each component and minimize the possibility of certain adverse events. – Use one component to antagonize one or more side effects of another component (e.g. laxation vs constipation)Antacids are used commonly in combination in order to:
– A soluble salt forms when it reacts with gastric acid but hydrolyzes to form insoluble bismuthyl salts (BiO+) – Does not neutralize gastric acid but coats the gastric walls and acts as a mechanical protective. – Forms a complex with the glycoprotein component of mucus that creates the protective barrier.Bismuth Compounds(MOA)?
Simethicone• An antifoaming agent • Decreases the tendency of gastroesophageal reflux.
Sucralfate• A sucrose sulfate-aluminum complex. • It forms an ulcer-adherent complex with the proteinaceous exudate at the ulcer site; this covers the ulcer site and protects it from further attack by pepsin and acid.


Question Answer
Catharticsaccelerate fecal passage
Laxatives decrease fecal consistency.

Types of Cathartics/Laxatives

Question Answer
StimulantStimulate water secretion into GIT, inhibit water absorption or increase motility.
Saline/Hyperosmoticexert osmotic effect that increases water content and volume of stool.
Lubricantallow easier passage of stool due to oil coating; may also inhibit colonic water absorption.
Bulk-forming(Selinium Fibr)absorb water, increasing the volume of stool.
Emollientsurfactants that facilitate mixture of water and lipid-soluble substances to soften stool; stimulate water secretion into GIT
Saline Cathartics• Sodium Phosphate • Sodium Phosphate and Sodium Biphosphate Enema • Sodium Phosphate and Sodium Biphosphate Oral Solution • Potassium Sodium Tartrate (Rochelle Salt) • Magnesium Sulfate (Epsom Salt) • Magnesium Oxide