Pharmacotherapy of GERD and PUD Flashcards
What are the classic symptoms of GERD?
Heartburn and regurgitation
What are other symptoms of GERD?
Dyspepsia,
Chest pain,
Belching,
Chronic cough
What are the standard treatments for GERD?
Medications that suppress gastric acid
What is the most common cause of PUD?
H. pylori
What are other causes for PUD?
Use of NSAIDs, including aspirin
Bile reflux
What is the treatment for healing the ulcers themselves?
PPI for ulcer healing
What is the function of parietal cells?
They are the “factory of H+”
What is the direct way of regulating acid secretion?
Acetylcholine, gastrin, and histamine stimulate the parietal cells, triggering the secretion of H+ into the lumen
What is the indirect way of regulation acid secretion?
Acetylcholine and gastrin also stimulate the ECL cell, resulting in the secretion of histamine which then acts on the parietal cells
What is the etiopathogenesis of peptic ulcer?
PUD: chronic mucosal ulceration affecting mostly the duodenum or stomach
It can occur in any part of the GIT
What is the function of the tubulovesicular structures?
Increase the apical surface, for instance allowing more space for the cell to produce HCl
What are the aggressive factors of peptic ulcers?
H. pylori
NSAIDs
Gastric acid
Pepsin
Smoking
What are the defensive factors of peptic ulcers?
Mucus
Bicarbonate
Blood flow
Prostaglandins
What is mucus and how is it a defensive factor?
It is a barrier that protects underlying cells from acid and pepsin, mucus is also an alkaline
What is bicarbonate and how is it a defensive factor?
Mostly remain trapped in the mucus where it neutralises the H+ (in duodenum, neutralises stomach acid)
What is blood flow and how is it a defensive factor?
Ischemia leads to injury, increasing vulnerability to acid and pepsin
What are prostaglandins and how is it a defensive factor?
They stimulate to secretion of mucus and bicarbonate and promote vasodilation, also suppresses acid secretion
What is H. pylori and why is it an aggressive factor?
It is a gram (-) bacteria which resides between epithelial cells and the mucus barrier
What are NSAIDs and why are they an aggressive factor?
They inhibit synthesis of prostaglandins
What is gastric acid and how is it an aggressive factor?
An absolute requirement for ulcer generation, however, not sufficient by itself to cause ulcers
What is pepsin and why is it an aggressive factor?
Can injure unprotected cells
What is smoking and how is it an aggressive factor?
Delays ulcer healing and increase the risk of recurrence
What is the classes of anti-ulcer dugs?
Antibiotics
Anti-secretory agents
Mucosal protectants
Antacids
Antisecretory agents that enhance mucosal defence
What are the examples of antibiotics?
Clarithromycin, Amoxicillin, Metronidazole, Bismuth
What receptor does acetylcholine bind to?
M3 muscarinic receptors
What receptors does CCK bind to?
CCK2
What receptors does histamine bind to?
H2 receptors
What is the effect of acetylcholine, CCK and H2?
Through a Ca2+ or cAMP (histamine) pathway they increase the function of the proton pump (H+/K+ ATPase)
What receptor do prostaglandins bind to? How do they work?
EP3 and the inhibit the cAMP pathway and thus inhibit the proton pump, less HCl production
Which is the most efficient treatment for blocking the H+/K+ ATPase?
PPIs
What is the function of Clarythromycin?
Inhibits protein synthesis of H. pylori
What are the side effects of Clarythromycin?
Nausea, diarrhoea, and distortion of taste
What is FDA update for clarithromycin?
Increased risk of CV events and death in patients with CAD
What is the function of Amoxicillin?
Disrupts cell wall
When is the activity of Amoxicillin ideal?
When the pH is neutral; thus reducing gastric acidity will enhance its activity
What can be used to reduce the gastric acidity in combination with Amoxicillin?
Omeprazole
What are the side effects of Amoxicillin?
Diarrhea
What is the function of Metronidazole?
Degradation of biological macromolecules and DNA chains
Which is the antibiotic which 40% of H. pylori has become resistant to?
Metronidazole
What are the adverse effects of Metronidazole?
Nausea and headaches
Metallic taste and some neurology effects (seizures)
What are the contraindications of Metronidazole?
Avoid alcohol consumption
What has caused the resistance of H. pylori to Metronidazole?
The misuse and the overuse
What is the function of Bismuth?
Acts topically to disrupt cell wall –> lysis of H. pylori
What are the side effects of Bismuth?
Harmless black coloration to the tongue and stool
What kind of inhibitor is Clarithromycin?
A very potent inhibitor of CYP3A4 and p-glycoprotein
What is the effect of taking Clarithromycin with drugs that prologs the QT interval?
Increase the risk of QT internal prolongation or tornadoes de pointes
What are the drug interactions of Metronidazole?
Inhibits CYP2C9 and may increase serum concentrations of drugs metabolised by this isozyme
What is an example of a drug metabolised by CYP2C9, and thus interacts with Metronidazole?
Warfarin
What are the first line regiments for eradicating H. pylori?
CLAR-based triple therapy 1
CLAR-based triple therapy 2
Bismuth-based quadruple therapy
Sequential therapy
What is CLAR-based triple therapy 1?
Standard dose PPI, clarithromycin 500mg, amoxicillin 1g
What is the duration of CLAR-based triple therapy 1?
10 to 14 days
What is the eradication rates of CLAR-based triple therapy 1?
70 to 85%
Which patients are given CLAR-based triple therapy 1?
In non-penicillin-allergi, macrolide negative patients
What is CLAR-based triple therapy 2?
Standard dose of PPI, clarithromycin 500mg, metronidazole 500mg
What is the duration of CLAR-based triple therapy 2?
10 to 14 days
What is the eradication rate of CLAR-based triple therapy 2?
70 to 85%
When is CLAR-based triple therapy 2 used?
In penicillin-allergic patients who are macrolide negative or unable to tolerate bismuth quadruple therapy
What is the Bismuth-based quadruple therapy?
Bismuth 525mg, Metronidazole 250mg, Tetracycline 500mg, Ranitidine 150mg, standard dose of PPI
What is the duration of the Bismuth-based quadruple therapy?
10 to 14 days
What is the eradication rate of Bismuth-based quadruple therapy?
75 to 90%
When is quadruple therapy given?
In penicillin-allergic patients
What is sequential therapy?
PPI + amoxicillin 1mg followed by: Psi, clarithromycin 500mg, tinadazole 500mg
What is the duration of sequential therapy?
5 days each
What is the eradication rate of sequential therapy?
> 90%
What are the comments regarding sequential therapy?
Required validation in North Africa
Which is the first line therapy now?
Bismuth-based quadruple therapy
What are the examples of H2R antagonists?
Cimetidine (Tagamet)
Ranitidine (Zantac)
What are H2R antagonists used for?
PUD
GERD
Heartburn
ZE syndrome
What are the side effects of of H2R antagonists?
Anti-androgenic effects
Pneumonia
What are the ant-androgenic effects caused by H2R antagonists?
Gynecomastia and decreases libido, maybe impotence (reversible)
How and why is pneumonia an adverse effect of H2R antagonists?
When acidity of stomach decreases, chance of bacterial colonisation increases, resulting in secondary increase in colonisation of the respiratory tract
What is the effect of cimetidine on hepatic enzymes?
It inhibits P450
What are the drugs that you should pay attention to when giving Cimetidine?
Warfarin, phenytoin, theophylline and lidocaine –> all have a narrow therapeutic index
If the therapeutic window is narrow and you increase the concentration –> more likely to have adverse and toxic effects
What is the effect of antacids on absorption of cimetidine?
Decrease absorption that is why they have to be given 1 hour apart
What is the effect of H2R antagonists on serum concentration of drugs that require gastric acid?
It decreases the serum concentrations of drugs which require gastric acid for absorption, such as Itraconazole, Rilpivirine and Atazanavir
What are the examples of PPIs?
Omeprazole,
Esomeprazole (Nexium),
Rabeprazole,
Lansoprazole,
Dexlansoprazole,
Pantoprazole
What is the function of the Omeprazole?
Irreversibly inhibits the H+/K+ ATPase
Inhibit CYP2C19
What are the uses of Omeprazole?
Used for ulcers, GERD, acid hyper secretion
What is the function of Esomeprazole?
Nearly identical to omeprazole; however, it is metabolised less slowly –> longer-lasting effects compared to omeprazole
Inhibit CYP2C19
What are the drug interactions of Omeprazole and Esomeprazole?
Reduces adverse and beneficial effects of clopidogrel (anti-platelet agent)
Inhibition of CYP2C19 –> inhibition of conversion of clopidogrel to its active metabolite (Plavix)
In what kind of patients do you not give Omeprazole/ Esomeprazole as a PPI?
The ones who you prescribe Clopidogrel to
You give alternative PPI
What is the function of Rabeprazole (Pariet)?
Reversible inhibits H+/K+ ATPase, effects are less durable
Also has antibacterial effects (helps eradicate H. pylori)
How are PPIs metabolised?
Partially by CYP2C19
What happens if patients have very active CYP2C19?
May have a decreased response to PPI treatment
What are the PK of PPIs?
PPIs are a prodrug; enteric coating removed in the alkaline environment of the duodenum
What is the half-life of PPIs like?
Short serum half-lives but duration of action is longer than H2R antagonists, allowing for once a day use
What is the tolerance of PPIs like?
Unlike H2RAs, tolerance to PPIs does nit occur with continuous use
What are the side effects of PPIs?
Headache, nausea, diarrhoea (increased risk of C. difficile infection), abdominal pain, vomiting, pneumonia, fractures
What is long term PPI use associated with?
Hypomagnesia and vitamin B12 deficiency
What is the function of Sucralfate ?
Promotes ulcer ealing by creating a protective barrier against pepsin and acid
What is Sucralfate used for?
Acute therapy and maintenance therapy of duodenal ulcers
Not as frequently used anymore
What is Misoprostol?
A prostaglandin E1 analogue
What is the function of Misoprostol?
Suppresses secretion of gastric acid,
Promotes secretion of bicarbonate and mucus
Maintains submucosal blood flow
Prevents NSAID-induced ulcers
How does Misoprostol prevent NSAID-induced ulcers?
By serving as a replacement for endogenous prostaglandins
What are antacids?
Alkaline compounds that neutralise stomach acid
What are examples of antacids?
Al(OH)3
Mg(OH)2
Ca(CO)3
NaHCO3
In what cases are antacids used?
Peptic ulcers, GERD, heartburn
What is the margin of safety of antacids like?
Wide margin of safety
What are the effects of antacids?
Decrease destruction of the gut wall
Reduces pepsin activity, if pH > 5
Enhances mucosal protection by stimulation production of prostaglandins
Which is the exception of antacids which is not poorly absorbed?
NaHCO3
What is the advantage of antacids being poorly absorbed?
Do not alter the pH
What are the adverse effects of antacids?
Al & Ca –> constipation
Mg & Na –> diarrhoea
What are some precautions when using antacids?
Some contain substantial amounts of sodium, avoid in patients with hypertension or CHF
Do not use Ca2+ with renal calculi
By raising gastric pH, they reduce the absorption of many drugs, allow for 1 between them
Which drugs’ absorption is affected by antacids?
Cimetidine and Ranitidine
What is Vonoprazan ?
Potassium-competitive acid blocker
Which diseases in Vonoprazan approved for?
Erosive and non-erosive GERD and heartburn
What are the side effects of Vonoprazan?
Indigestion
Stomach upset
Tenderness in stomach region
Burning feeling in stomach or chest
How is Vonoprazan metabolized?
Mainly by CYP450, CYP3A4 and to some extent by CYP2B6, CYP2C19, CYP2D6, and SULT2A1
How is Vanoprazal eliminated?
In urine (67%) and feces (31%)