39 Questions
Which type of receptors do Histamine Type 2 Receptor Antagonists target?
Histamine Type 2 receptors
Which class of acid-lowering drugs requires activation?
Proton Pump Inhibitors
What is the advantage of Potassium-Competitive Acid Blockers over Proton Pump Inhibitors?
Faster onset of action
Which drug demonstrates anti-microbial activity, stimulates bicarbonate secretion, and forms a protective barrier along the surface of gastric epithelial cells?
Sucralfate
Which class of acid-lowering drugs primarily undergoes renal elimination?
Histamine Type 2 Receptor Antagonists
What is the name of the novel Potassium-Competitive Acid Blocker?
Vonoprazan
Which type of agents stimulate gastrointestinal motility and are used in the treatment of GERD?
Prokinetic agents
What is the primary mechanism of action of Proton Pump Inhibitors?
Blocking the H+/K+ ATPase enzyme
Which type of agents are used to eradicate H. pylori infection?
Antibiotics
What type of cells in the stomach are responsible for producing acid?
Parietal cells
Which of the following reduces gastric acid production?
Excess acid
What is the primary effect of H2 receptor antagonists?
Decrease in gastric acid secretion
What is the most common indication for H2 receptor antagonists?
Gastroesophageal reflux disease (GERD)
Which of the following is NOT a factor that regulates gastric acid production?
Epinephrine
What is the mechanism of action of H2 receptor antagonists?
Blockade of histamine receptors
What is the effect of histamine on gastric acid production?
Increase in gastric acid production
What is the primary site of action for H2 receptor antagonists?
Parietal cells
What is the duration of action of H2 receptor antagonists?
24 hours
What is the primary indication for H2 receptor antagonists in terms of timing?
Before bedtime
What is the mechanism of action of potassium-competitive active blockers?
Inhibit the ability of H+/K+ ATPase to bind to potassium, effectively inhibiting the pump
What is the advantage of vonoprazan over PPIs?
It is more effective in killing H. pylori and has faster healing rates from bleeding
What is the mechanism of action of antacids?
They react with gastric HCl to form a salt and water
What is the primary mechanism of action of misoprostol?
It stimulates the production of mucus and bicarbonate secretion
What is the mechanism of action of dopamine receptor antagonists in the gut?
They antagonize the action of dopamine in the gut, increasing LES tone and gastric emptying rate
What is the primary mechanism of action of erythromycin?
It is a macrolide antibiotic that acts as a ligand for the motilin receptor
What is the primary difference between PPIs and H2R antagonists?
PPIs inhibit the H+/K+ ATPase, while H2R antagonists inhibit histamine receptors
What is the primary advantage of mucosal protective agents?
They increase the protective mechanisms of the gastric lining
What is the primary mechanism of action of bismuth subsalicylate?
It has antimicrobial activity, stimulates bicarbonate secretion, and forms a protective barrier
What is the primary mechanism of action of prokinetic agents?
They stimulate gastrointestinal motility and increase LES tone
Which of the following H2 receptor antagonists has the greatest affinity for the H2 receptor?
Famotidine
What is the primary mechanism of action of proton pump inhibitors?
Irreversible inactivation of the H/K ATPase
Which of the following H2 receptor antagonists is contraindicated in renal dysfunction?
Nizatidine
What is the primary reason for administering proton pump inhibitors 1 hour before a meal?
To coincide with the peak activity of proton pumps
Which of the following is a potential interaction of omeprazole with another drug?
Warfarin
What is the primary mechanism of metabolic activation of proton pump inhibitors?
Protonation of the pro-drug
Which of the following is a characteristic of H2 receptor antagonists?
Little effect on cytochrome P450s
What is the primary reason for the long duration of action of proton pump inhibitors?
Irreversible binding of the pump
Which of the following is a side effect of H2 receptor antagonists?
Diarrhea
What is the primary mechanism of action of ranitidine?
Blockade of H2 receptors
Study Notes
Pharmacology of Gastric Acid Lowering Drugs
Overview of Gastrointestinal Disorders
- Most common gastrointestinal disorders: peptic ulcer disease (gastric or duodenal in origin), gastroesophageal reflux disease (GERD), drug-induced injury, hypersecretory states (Zollinger-Ellison disease), and stress-related mucosal injury
Physiology of Acid Production
- Gastric acid is produced by parietal cells in the stomach fundus
- Factors that regulate gastric acid production: Acetylcholine (+), Histamine (+), Gastrin (+), GRP (+), Excess acid (-) (via Somatostatin), Gastric inhibitory peptide (GIP) (-), Prostaglandin E2 (-), and EGF (-)
Mechanism of Gastric Acid Lowering Drugs
- Histamine Type 2 Receptor Antagonists (H2RAs):
- Reduce volume of gastric secretion and concentration/acidity
- Effective in treating basal acid secretion (at night)
- Examples: Ranitidine (Zantac), Famotidine (Pepcid), Nizatidine
- Adverse Effects: Minor side effects (diarrhea, headache, drowsiness, fatigue, constipation), Cimetidine inhibits binding of dihydrotestosterone to androgen receptors, crosses placenta, and is secreted in breast milk
Proton Pump Inhibitors (PPIs)
- Weak bases that concentrate in acidic environments (1000-fold more concentrated in stomach than elsewhere in the body)
- Pro-drugs that require activation; the active drug interacts with H/K ATPase, irreversibly inactivating the enzyme
- Examples: Omeprazole, Esomeprazole, Lansoprazole, Dexlansoprazole, Pantoprazole, Rabeprazole
- Indicated for GERD and peptic ulcers, and in combination treatment of H. pylori infection
- Pharmacokinetics: rapid first-pass hepatic metabolism, negligible renal clearance, highly plasma protein bound, and polymorphisms in CYP2C19 may affect efficacy and toxicity
Adverse Effects of PPIs
- Generally well tolerated, but may cause nausea, abdominal pain, flatulence, diarrhea, and interact with clopidogrel
Potassium-Competitive Active Blockers (PCABs)
- Inhibit ability of H/K ATPase to bind to potassium, effectively inhibiting the pump
- Example: Vonoprazan (approved in Japan, pending approval in North and South America)
- Advantages over PPIs: no need for protonation for activity, more consistent lowering of gastric pH, and less frequent bacterial resistance
Antacids
- Weak bases that react with gastric HCl to form a salt and water
- Examples: Sodium Bicarbonate, Calcium Carbonate, Magnesium/Aluminum Hydroxides
- Adverse Effects: Metabolic alkalosis, gastric distension, belching, and binding of other drugs (ACE inhibitors, quinolone antibiotics, ASA, NSAIDS, levothyroxine, glyburide, and misoprostol)
Mucosal Protective Agents
- Prostaglandins (Misoprostol): stimulate mucus and bicarbonate secretion, increase mucosal blood flow, and have anti-inflammatory properties
- Bismuth Subsalicylate: part of quadruple therapy for H. pylori infections, inhibits pepsin activity, and increases mucous production
Prokinetic Agents
- Dopamine Receptor Antagonists (e.g., Domperidone): increase esophageal peristalsis, increase LES tone, and increase gastric emptying rate
- 5-HT Agonists (e.g., Prucalopride): stimulate peristalsis, increase LES tone, and increase gastric emptying rate
- Erythromycin: ligand for the motilin receptor, increases LES tone, and increases gastric emptying rate
This quiz covers the pharmacology of drugs used to treat peptic ulcers and GERD, including proton pump inhibitors, histamine type 2 receptor antagonists, and antacids. It also explores the therapy of H. Pylori infection and prokinetic drugs for treating GERD.
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