Peptic ulcer and reflux disease Flashcards
List the causative factors of peptic ulcer disease.
Increase gastric acid and/or pepsin
Reduced mucosal blood flow, duodenal bicarbonates, thickness of mucosal layer
NSAIDs, smoking
List the different types of anti-secretory drugs for PUD.
H2-receptor antagonists
Proton pump inhibitors
Anti-muscarinic drugs
List the different types of cytoprotective agents and mucosal strengtheners.
Sucralafate
Prostoglandins
Bismuth
Antacids
Describe the mechanism of action of proton pump inhibitors.
Weak bases, accumulate and activated in the canaliculi by acidic environment. Bind covalently to extracellular domain of H+/K+ATPase, 90% inhibition. Lasts 2-3 days
Give examples of proton pump inhibitors.
Esomeprazole
Pantoprazol
What is class of drugs that esomeprazol belongs to?
Proton pump inhibitors
Describe the kinetics of proton pump inhibitors.
Administered in capsules, 1 hours before meals, not coadministed with other acid suppressing agents
List the ADRs of proton pump inhibitors.
Gynaecomastia, renal impairment, headache, skin rashes, dizziness.
Old formulations inhibit CYP450
Describe histamine receptor antagonists for the use of PUD.
Reversible competitive inhibitors of H2 receptors.
Better for inhibiting nocturnal acid secretion, promotes healing of duodenal ulcers, relapse with withdrawal.
Give an example of histamine receptor antagonist used for PUD.
Ranitidine
What class of drugs does ranitidine belong to?
Histmine receptor antagonist.
List the side effects of histamine receptor antagonists.
Impotence, gynaecomastia.
Cimetidiene interferes with CYP450
Describe the pharmacokinetics of histamine receptor antagonists
Absorbed orally, high renal excretion.
Why are antimuscarinics rarely used for PUD?
Significant side effects - skin rashes, gastric stasis.
Why are gastrin antagonists rarely used for PUD?
Experimental, poor effectiveness, not used in Australia
Why are somatostatin analogues rarely used for PUD?
Require i.v. administration
Describe the mechanism of action of sucralfate.
Complex of aluminium hydroxide and sulfated sucrose.
Viscous at acid pH, adheres to ulcers as a barrier
Stimulates mucosal protecting mechanisms (mucus, bicarbonate, PGs)
List the ADRs of sucralfate.
Constipation, inhibit absorption of some drugs - theophylline, tetracycline, digoxin, amitriptyline.
How is sucralfate used?
On an empty stomach 1h before meals
Not to be taken with antacids and meals to not alter pH
What class of drugs does misoprostol belong to?
PGE1 analogue
What is the therapeutic effect of prostaglandin analogues?
Inhibit acid secretion, increase mucosal blood flow and mucous, cytoprotective on gastric mucosa.
List the ADRs of prostaglandin analogues.
Pain sensitisation initially, uterine contractions, diarrhoea, nausea, headache, dizziness.
What are the clinical considerations for misoprostol (PGE1 analogue)?
Only for NSAID users
Ulcer healing
What is the mechanism of action of bismuth chelate?
Coats ulcer base
Enhances PG synthesis, stimulates mucus and bicarbonate secretion
Moderate direct antimicrobial activity
