GI Management Flashcards
What is the first line treatment to GORD?
Proton pump inhibitor
What medication is added secondary to a lack of response to PPI?
H2 receptor antagonists
Name a PPI
Omeprazole Esomeprazole Rabeprazole Pantoprazole Lansoprazole
What is the common therapy administered for eradication of H.pylori and its duration?
10-14 days
PPI +amoxicillin+clarithromycin/metronidazole
Or
PPI+bismuth+2xantibiotics (if previously taken macrolide/metronidazole)
What is given to patients with autoimmune chronic gastritis (pernicious anaemia)?
Cyanocobalamin treatment (B12)
Which prostaglandins are considered gastric prostaglandins?
PGE2 and PGI2
What is the role of prostaglandins in the GI system?
- potent vasodilator
- decrease acid secretion
- stimulate mucus and bicarbonate secretion
- reduce permeability of acid back flow
- reduce inflammatory mediator release
- promote ulcer healing
What is the mechanism of action of antacids?
Relieve dyspepsia as they neutralise HCl, reacting with the acid to form water and salt.
what are some of the common preparations of antacids?
Aluminium hydroxide
Magnesium hydroxide
Sodium bicarbonate
Calcium bicarbonate
What patient groups must avoid sodium bicarbonate ?
Hypertension
Fluid overload
What patients should avoid magnesium hydroxide?
Renal failure- causes increased magnesium
what adverse side effect can be caused by magnesium hydroxide?
Diarrhoea
What side effects may be experienced with aluminium hydroxide?
Constipation
Binding of phosphate resulting in lower levels- weakness and malaise
Neurotoxicity in presence of renal failure
What patient group should avoid taking aluminium hydroxide?
Renal failure- neurotoxicity.
Name a prostaglandin analogue and its mechanism of action?
Misoprostol
Acts on PGE2 and affects similar pathway to H2 RAs
What are the side effects and contraindications of prostaglandin analogues?
Side effects: diarrhoea and abdominal pain
Contraindications: pregnancy - induce uterine contractions (can be used in pp haemorrhage).
What is the mechanism of action of H2 RAs?
Competitively and reversible inhibition of histamine to H2 receptors. Reduces PK and therefore not changing shape, not allowing proton pumps to be expressed.
Indirectly block effects of gastrin and Ach on parietal cells.
What is the common side effects of H2 RAs?
Diarrhoea Constipation Muscle ache Fatigue Reduced ketoconazole absorption (needs acidic environment)
Name a H2 RA?
Cimetidine
Why is cimetidine used less frequently?
Inhibits CYP450 enzymes, decreasing metabolism of lidocaine, phenytoin, theophylline and warfarin.
Potentially results in toxic levels.
Describe the non-secreting state of the parietal cells
Proton pumps are located in the membrane bound compartment (tubulovesicles). These lack K permeability, blocking H/K ATPase activity.
Describe the transition of non-secreting to a secreting state in a parietal cell
Apical membrane of the parietal cell has involutions (canaliculi), they have microvilli.
In the secreting state, tubulovesicles fuse with canalicular membrane. Moves proton pump to apical surface.
This involves a huge movement of membrane to canaliculi and elongation of microvilli.
What is the mechanism of action of PPI
Pro drugs - they are weak bases and accumulate in the acidic space of the secretory canaliculus.
Bind covalently to H/K ATPase irreversibly and block function. Prolonged and nearly complete suppression of acid secretion.
What are the potential side effects of PPI?
Headache
Nausea
GIT issues
Abdominal pain
what are the potential issues with PPIs?
Increased level of gastrin - parietal cell and ECL hyperplasia, some concern could increase gastric carcinoid tumours.
May decrease effectiveness of clopidogrel - both use CYP2C19.
Increase risk of hip fractures (increased stomach pH may reduce gastric absorption of soluble calcium).
Increase risk of various infections within hospitals.
What patient groups should avoid sodium bicarbonate as an antacid?
Hypertension and oedematous
What is the mechanism of H2 RA excretion?
Liver and kidney
PPI s need a coating because?
Enteric coating prevents premature activation (prodrug)
What are the potential issues with PPIs?
Metabolised by CYP P450 - decrease clopidogrel effectiveness
Liver failure
Excreted by kidney
Increased risk of hip fracture - decreased calcium absorption
Increased risk of infection in hospital- loss of barrier
Misoprostol is used when NSAIDs are needed, hoe does it work?
Inhibit adenylate cyclase and therefore decrease proton pump activity
