Drugs Affecting Gastrointestinal Function

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Sucralfate's effectiveness can be reduced when administered with which type of medication?

Proton pump inhibitors
Histamine H2 receptor antagonists
Bismuth chelate
Antacids (correct)

What is the primary reason for the limited use of sucralfate despite its effectiveness in treating duodenal ulcers?

Availability of more effective agents and multiple daily dosing. (correct)
Severe adverse effects
Single daily dosing
High cost of treatment

Misoprostol is an analog of which prostaglandin?

Prostaglandin F2
Prostaglandin E2
Prostaglandin E1 (correct)
Prostaglandin I2

What is a key mechanism of action of Misoprostol on gastric acid secretion?

Exerting a direct action on the ECL cell, inhibiting basal gastric acid secretion. (C) Signup and view all the answers

Why is Misoprostol contraindicated during pregnancy?

It can cause uterine contractions. (B) Signup and view all the answers

Which of the following is a clinical application of Histamine H2 receptor antagonists?

Reflux oesophagitis (B) Signup and view all the answers

Which medication is used as one component of therapy for Helicobacter pylori infection?

Bismuth chelate (A) Signup and view all the answers

Which class of drugs is primarily used in the treatment of Zollinger-Ellison syndrome?

Proton pump inhibitors (B) Signup and view all the answers

Why does cimetidine sometimes cause gynecomastia and decreased sexual function in men?

It possesses a modest affinity for androgen receptors. (D) Signup and view all the answers

Cimetidine can potentiate the action of oral anticoagulants because it:

Inhibits cytochrome P450, retarding the metabolism of certain drugs. (B) Signup and view all the answers

What is the mechanism of action of omeprazole in reducing gastric acid secretion?

It irreversibly inhibits the H+-K+-ATPase (proton pump). (A) Signup and view all the answers

Why are proton pump inhibitors (PPIs) like omeprazole administered as enteric-coated granules in capsules?

To prevent their degradation in the acidic environment of the stomach. (B) Signup and view all the answers

For optimal efficacy, when should proton pump inhibitors (PPIs) be taken?

30 to 60 minutes before breakfast or the largest meal of the day. (C) Signup and view all the answers

Why do proton pump inhibitors (PPIs) have a long duration of action despite having a short plasma half-life?

They form a covalent bond with the H+/K+-ATPase enzyme. (D) Signup and view all the answers

Why is the concomitant use of omeprazole and clopidogrel not recommended?

Omeprazole inhibits CYP2C19, preventing the conversion of clopidogrel to its active metabolite. (A) Signup and view all the answers

Why may prolonged use of proton pump inhibitors (PPIs) lead to low vitamin B12 levels?

Acid is required for the absorption of vitamin B12 in a complex with intrinsic factor. (D) Signup and view all the answers

Which of the following is NOT a primary function of hydrochloric acid (HCl) secreted in the stomach?

Neutralizing excess bicarbonate ions. (D) Signup and view all the answers

How do locally produced prostaglandins protect the gastric mucosa?

By stimulating the secretion of both mucus and bicarbonate. (D) Signup and view all the answers

Which cellular mechanism is directly responsible for pumping H+ ions into the stomach lumen?

K+-H+-ATPase (Proton pump) (B) Signup and view all the answers

What role does carbonic anhydrase play in parietal cells during gastric acid secretion?

It catalyzes the production of bicarbonate ions and H+ from carbon dioxide and water. (B) Signup and view all the answers

Which of the following mediators inhibits gastric acid secretion?

Somatostatin (C) Signup and view all the answers

How does histamine stimulate acid secretion in parietal cells?

By activating H2 receptors, leading to increased cAMP levels. (A) Signup and view all the answers

What is the primary role of enterochromaffin-like (ECL) cells in the gastric mucosa?

Releasing histamine to stimulate acid secretion. (D) Signup and view all the answers

How does the bicarbonate secreted by the gastric mucosa protect the stomach lining from the acidic environment?

By creating a gel-like barrier with a higher pH near the mucosal surface. (A) Signup and view all the answers

Why are antacids commonly formulated as a combination of magnesium and aluminum salts?

To minimize the individual side effects of diarrhea (caused by magnesium salts) and constipation (caused by aluminum salts). (B) Signup and view all the answers

Eradication of Helicobacter pylori (H. pylori) is crucial in treating ulcers because this action directly leads to:

The rapid and sustained healing of ulcers and reduces the risk of gastric cancer. (C) Signup and view all the answers

A patient tests positive for H. pylori and is prescribed 'triple therapy'. What does this regimen typically include?

A proton pump inhibitor (PPI), amoxicillin, and metronidazole or clarithromycin. (B) Signup and view all the answers

Bismuth chelate exerts its therapeutic effect in treating H. pylori infections through which of the following mechanisms?

Direct toxic effects on the bacillus, prevents its adherence to the mucosa, and increases mucus secretion. (A) Signup and view all the answers

What is a potential risk associated with bismuth chelate administration, especially in patients with impaired renal function?

Encephalopathy from raised plasma concentrations of bismuth. (D) Signup and view all the answers

How does sucralfate protect the gastric mucosa?

By forming a complex gel with mucus, limiting H+ ion diffusion, inhibiting pepsin, and stimulating secretion of mucus, bicarbonate, and prostaglandins. (B) Signup and view all the answers

Which of the following best describes the primary mechanism through which sucralfate promotes ulcer healing?

Forms a protective barrier that binds to the ulcer base, preventing further damage from acid and pepsin. (C) Signup and view all the answers

How does sucralfate affect mucus within the stomach?

It forms complex gels with mucus, thought to decrease mucus degradation by pepsin. (C) Signup and view all the answers

Which of the following mechanisms describes how acetylcholine stimulates acid secretion in parietal cells?

Stimulation of muscarinic M3 receptors, leading to increased intracellular calcium. (A) Signup and view all the answers

Prostaglandins, such as PGE2 and I2, exert cytoprotective effects in the GI tract by which mechanism?

Increasing bicarbonate secretion, enhancing mucin release, and reducing gastric acid output. (B) Signup and view all the answers

A patient with Zollinger-Ellison syndrome experiences gastric acid hypersecretion due to a gastrin-producing tumor. Which class of drugs would be most effective in managing this condition?

Histamine H2 receptor antagonists (C) Signup and view all the answers

Why is long-term, untreated GORD a concern?

It can cause dysplasia of the oesophageal epithelium, potentially progressing to Barrett oesophagus. (B) Signup and view all the answers

What is the primary mechanism by which non-specific NSAIDs contribute to gastric bleeding and erosions?

Inhibition of cyclo-oxygenase I, reducing the synthesis of protective prostaglandins. (A) Signup and view all the answers

How do histamine H2-receptor antagonists reduce gastric acid secretion?

By competitively inhibiting histamine actions at H2 receptors on parietal cells. (B) Signup and view all the answers

A patient is prescribed cimetidine for peptic ulcer disease. What is the most important consideration regarding the administration and absorption of this drug?

It is generally well absorbed orally, although intramuscular and intravenous formulations are available. (B) Signup and view all the answers

Misoprostol, a synthetic prostaglandin, is used to prevent NSAID-induced gastric ulcers. What is its primary mechanism of action in this context?

Mimicking the protective effects of endogenous prostaglandins on the gastric mucosa. (C) Signup and view all the answers

Cimetidine and Gynaecomastia

Side effect of cimetidine where men develop breast tissue.

Cimetidine & Cytochrome P450

Cimetidine inhibits this, affecting metabolism of other drugs like oral anticoagulants.