DSA: Tx of PUD and GERD - SRS Flashcards
What classes of agents which reduce gastric activity do we need to be aware of?
- PPI
- H2-Receptor Antagonists (H2RAs)
- Antacids
Give me 6 PPIs we need to know?
- Dexlansoprazole (Dexilant)
- Esomeprazole (Nexium)
- Lansoprazole (Prevacid)
- Omeprazole (Prilosec, Zegerid)
- Pantoprazole (Protonix)
- Rabeprazole (Aciphex)
What are four H2-Receptor Antagonists (H2RAs)?
- Cimetidine (Tagamet)
- Famotidine (Pepcid)
- Nizatidine (Axid)
- Ranitidine (Zantac)
What are three antacits we covered?
- Sodium bicarbonate (baking soda, Alka Seltzer)
- Calcium carbonate (Tums, Os-Cal)
- Magnesium hydroxide/aluminum hydroxide (Mylanta, Maalox)
What are four agents that can be used to provide mucosal protection?
- Bismuth subcitrate
- Bismuth subsalicylate (Pepto-Bismol)
- Misoprostol
- Sucralfate (Carafate)
What are 4 antibiotics that we use in the treatment of H. pylori?
- Amoxicillin
- Clarithromycin
- Metronidazole
- Tetracycline
In addition to antibiotic therapy, what else should be employed in the treatment of H. pylori infection?
PPI or H2-Receptor Antagonists should be combined with two or more antibiotics
What are three factors that regulate acid secretion through receptor binding on parietal cells?
What type of substance is each?
AcH - neuronal
histamine - paracrine
gastrin - endocrine
How do parietal cells play into the secretion of acid?
- ACh (vagal postganglionic nerves) and gastrin (antral G cells) bind parietal receptors (muscarinic M3 and CCK-B respectively) and stimulate G-protein coupled receptor (GPCR) signaling pathways.
- Gq-PLC-IP3-Ca2+ activation leads to an increase in cytosolic Ca2+ which ultimately results in stimulation of acid secretion from H+/K+-ATPase (proton-pump).
- H+/K+-ATPase exchanges hydrogen and potassium ions across the parietal cell membrane.
How do enterochromaffin-like cells play into acid secretion?
- ACh and gastrin also bind gut endocrine cells called enterochromaffin-like (ECL) cells in close proximity to parietal cells which stimulates histamine release.
- Histamine released from ECL cells binds H2 receptors on parietal cells and activates the proton-pump via cAMP-dependent GPCR signaling pathways (Gs-adenylyl cyclase-cyclic AMP-PKA).
What is the role of somatostatin in acid secretion?
What produces it?
Produced by antral cells, somatostatin inhibits gastric secretion.
What do prostaglandins do in the way of acid regulation in the stomach?
- Prostaglandins E2 and I2 inhibit the proton-pump by reducing cAMP production (EP3 receptors are GPCRs coupled to Gi on parietal cells).
- PGE2 and PGI2 also stimulate production of protective factors (mucus, bicarbonate) by superficial epithelial cells and enhance mucosal blood flow.
What drugs block prostaglandins?
NSAIDs - block prostaglandin production leading to more acid, less mucus and less bicarbonate as well as decreased blood flow.
NSAIDs are ulcerogenic and should be avoided in PUD or at least dose reduced.
What lifestyle modifications are adviseabe for patients with acid-peptic diseases?
- Weight loss in overweight individuals or those who have recently gained weight.
- Head of bed elevation if symptoms associated with recumbency.
- Avoid meals 2-3 hours before bedtime in those with nocturnal GERD.
- Smoking cessation (tobacco effects lower esophageal sphincter).
- Cessation of foods that may aggravate reflux (limited or no clinical evidence but recommended if patient experiences symptom relief after cessation): caffeine, coffee, chocolate, spicy foods, acidic foods, high fat content foods.
What are the pharmacotherapy recommendations for GERD at the following levels?
- Mild, intermittent symptoms –
- Non-erosive disease –
- Erosive esophagitis –
- Mild, intermittent symptoms – antacid or H2RA as needed.
- Non-erosive disease – antacid or H2RA (PPI may be required in more severe symptoms).
- Erosive esophagitis – PPI for 8 weeks.
Most GERD drugs are category B for pregnancy and safe. One exception exists, what is it?
Omeprazole - category C, risk cannot be ruled out
In a pregnant patient with GERD, what are the recommendations for the following?
- Mild cases –
- Persistent symptoms –
- Intractable symptoms/complicated reflux –
- Mild cases – antacid or sucralfate.
- Persistent symptoms – H2RA (ranitidine has most safety data available).
- Intractable symptoms/complicated reflux – PPI (lansoprazole or pantoprazole preferred).
PUD presents with mucosal damage secondary to pepsin and gastric acid occurring in the stomach (gastric ulcer) or proximal duodenum (duodenal ulcer). What are some key causes?
- H. pylori
- Chronic NSAID use
- Zollinger-Ellison Syndrome
- Stress-related mucosal injury (d/t poor perfusion in critically ill patients)
In PUD, what are the pharmacotherapy recommendations for the following?
- Initial management –
- Duodenal ulcer –
- Gastric ulcer –
- H. pylori eradication –
- Initial management – withdrawal of offending/contributing factors, eradication of H. pylori.
- Duodenal ulcer – H2RA or PPI for 4 weeks.
- Gastric ulcer – PPI for 8 weeks.
- H. pylori eradication – Antisecretory agent (PPI preferred) plus at least two antibiotics (see page
In treating GERD and PUD you can approach it from two directions,
- Agents which reduce gastric acidity
- Agents which promote mucosal defense
Give 3 examples of each.
- Agents which reduce gastric acidity (PPIs, H2RAs, antacids).
- Agents which promote mucosal defense (bismuth compounds, misoprostol, sucralfate).
PPIs include : dexlansoprazole, esomeprazole, lansoprazole, omeprazole, pantoprazole, rabeprazole. What is their MOA?
- inactive prodrugs, lipophilic weak bases diffuse readily across lipid membranes into acidified compartments (parietal cell canaliculus)
- from the alkaline intestinal lumen. Rapidly becomes protonated and undergoes conversion to active form which forms a covalent disulfide bond with H+/K+-ATPase, irreversibly inactivating the enzyme.
PPI drugs could be called ideal drugs from a PK perspective, why?
ideal drugs from a PK perspective as they have short serum half-lives, concentrated and activated near site of action, and have a long duration of action.