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Questions and Answers
What is the mechanism of action of salt-containing osmotic agents?
Which of the following laxatives is used rectally?
What is the onset of action of salt-containing osmotic agents after oral administration?
Which of the following is a limitation of mineral oil as a laxative?
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What is the main use of salt-containing osmotic agents?
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Which of the following is a bulk-forming laxative?
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What is the effect of lubricant laxatives on the absorption of water?
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What is the route of administration of sodium phosphates?
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What is the mechanism of action of osmotic agents, salt-free?
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What is the effect of adequate hydration on the action of osmotic agents?
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Study Notes
Stress-related Gastritis
- Act as prophylaxis for recurrent ulcers in patients at risk
- Can be treated with proton-pump inhibitors (PPIs) such as omeprazole, which reduces both meal-stimulated and basal acid secretion
Proton-pump Inhibitors (PPIs)
- Irreversible inhibitors of the H+/K+-ATPase proton pump in parietal cells
- Block the transport of acid from the cell into the lumen
- Indications: gastroesophageal reflux disease (GERD), peptic ulcer disease, nonulcer dyspepsia, stress-induced gastritis, and gastrin-secreting tumors (Zollinger-Ellison syndrome)
- Adverse effects: headaches, gastrointestinal disturbances, and reduction in acid production may permit bacterial overgrowth
- Major drug interactions: inhibit the metabolism of other drugs like warfarin, can result in drug toxicity
Prostaglandins
- Misoprostol (Cytotec) is a methyl analog of PGE1 that acts on parietal cells to inhibit acid secretion and stimulate bicarbonate and mucus production
- Increases uterine contractions
- Clinical uses: prevention of NSAIDs-induced ulcer, termination of pregnancy, and induction of labor (off-label)
- Side effects: diarrhea, abortion, premature birth, birth defects, and uterine rupture (life-threatening)
Protective Agents
- Sucralfate (Carafate) is a polysaccharide complexed with aluminum hydroxide that protects ulcerated areas from further damage and promotes healing
- Effects: stimulates mucosal production of prostaglandins, inhibits pepsin, and has side effects of constipation and nausea
- Used in critical care settings for stress-related gastritis
Antacids
- Weak bases taken orally to partially neutralize gastric acid and reduce pepsin activity
- Reduce the pain associated with ulcers and may promote healing
- Prototype agents: sodium bicarbonate, calcium carbonate (TUMS, Os-Cal)
Other Agents
- Histamine1 (H1)-receptor antagonists: doxylamine + Vit B6, meclizine, and promethazine, used to treat motion sickness and morning sickness
- Dopamine antagonists: metoclopramide, used to treat nausea and vomiting, with side effects of sedation, diarrhea, and motor dysfunction
- 5-HT3 antagonists: ondansetron, used to treat nausea and vomiting, with side effects of mild constipation
- Benzodiazepines: lorazepam, diazepam, used as anxiolytic agents to reduce anticipatory emesis
Agents Used to Treat Diarrhea
- Opiates and opioid-containing preparations: act directly on opiate µ-receptors to decrease GI motility and increase transit time
- Diphenoxylate: a synthetic morphine analogue used to treat diarrhea
- Loperamide: an opioid agonist with no CNS activity, used to treat diarrhea, with a potential for severe constipation
- Bulk-forming laxatives: psyllium and methylcellulose, used to treat constipation
- Osmotic agents: magnesium citrate, magnesium sulfate, magnesium hydroxide, and sodium phosphates, used to treat constipation
- Lubricant laxatives: mineral oil and glycerin, used to treat constipation, with limitations of decreasing absorption of fat-soluble vitamins
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Description
Learn about the mechanisms of proton-pump inhibitors, such as omeprazole, in preventing stress-related gastritis and recurrent ulcers. Understand how they work to block acid transport in parietal cells.
