GI Pharmacology Flashcards
Risk factors of gastric and duodenal ulcers
- Helicobacter pylori
- NSAIDs
- early gastric emptying
- smoking + alcohol delay healing
Common causes of gastric + duodenal ulcers
Helicobacter pylori (most common)
NSAIDs
Example of alginates + antacids
Gaviscon
What class of drug is gaviscon?
Alginate + antacid
What are the uses of gaviscon?
GORD
What is the mechanism of action of gaviscon?
- antacid: buffers stomach acid
- alginic acid: increase stomach content viscosity + reduce reflux
What is gaviscon composed of?
- alginic acid: sodium alginate
- antacid: aluminium hydroxide/magnesium carbonate
What are adverse drug reactions of gaviscon?
Magnesium salts can cause diarrhoea
Aluminium salts can cause constipation
Why is the antacid part of gaviscon often composed of both aluminium hydroxide AND magnesium carbonate?
- magnesium salts can cause diarrhoea
- aluminium salts can cause constipation
- attempt to balance out the adverse drug reactions
. - magnesium hydroxide gastric pH higher + faster than aluminium hydroxide (AlHO has longer duration)
What are contradictions of gaviscon?
- renal failure in Na+ + K+ containing preparations
- diabetes mellitus in high sucrose conc preparations
What are important drug drug interactions of gaviscon?
- Can reduce absorption of drugs so doses should be separated
- Increased urine alkalinity can increases aspirin excretion
Examples of proton pump inhibitors
Omeprazole
Lansoprazole
What are the uses of PPIs?
Helicobacter pylori eradication
Peptic ulcers + relapse prevention
Co prescribed within NSAIDs
What is the mechanism of action of PPI?s
Irreversibly inhibition H+/K+ ATPase in parietal cells > reduction in acid secretion
What are adverse drug reactions of PPIs?
- abdominal pain
- diarrhoea
- constipation
- headache
- dizziness
- drowsiness
- can mask symptoms of gastro-oesophageal cancer
What are important drug drug interactions of PPIs?
- Omeprazole is a CYP inhibitors > reduced clopidogrel action
- increased effects of warfarin + phenytoin
What is the suffix of PPIs?
-prazole
Example of H2 receptor antagonists
Ranitidine
What are uses of H2 receptor antagonists?
Peptic ulcers
GORD
What is the mechanism of action of H2 receptor antagonists?
- Inhibition of H2 receptors
- Reduces release of histamines
- Reduces acid secretion from parietal cells
What are adverse drug reactions of H2 receptor antagonists?
Generally well tolerated
Diarrhoea
Headache
Can mask symptoms of gastro-oesophageal cancer
What are important drug drug actions of H2 receptor antagonists?
Few common
A patient is taking clopidogrel + the doctor wants to prescribe a PPI for their duodenal ulcer. Which PPI should they be given + why?
Lansoprazole
Omeprazole is a CYP inhibitor > reduces clopidogrel action
How should a PPI be prescribed?
Shorted effective duration at lowest effective dose
Treatment of Helicobacter pylori infection - triple therapy options
Lansoprazole + clarithromycin + amoxicillin
(metrondiazole if allergic to amoxicillin)
Diagnosis of Helicobacter pylori infection
Positive urea breath test
Example of aminosaicylates
Mesalazine
Sulfasalazine
What class of drug is mesalazine?
Aminosalicylate
What is the use of mesalazine?
First line treatment of UC
What is the mechanism of action of mesalazine?
Release of 5-aminosalsylic acid
Anti-inflammatory effect
Topic action at colon
What are adverse drug reactions of mesalazine?
Nausea
Dyspepsia
Leukopenia (rare)
What are important drug drug interactions of mesalazine?
Increased breakdown in presence of PPI due to increased pH
Compare the use of mesalazine + sulfasalazine
Mesalazine - first line for UC
Sulfasalazine - RA
The half life of PPIs is only a few hours, why is acid secretion inhibited for longer than this?
PPIs irreversibly inhibit H+/K+ ATPase in parietal cells
What drug is used first line in treatment of UC?
Mesalazine
