Gastrointestinal Flashcards
What are the indications for the use of PPIs?
- Peptic ulcers
- GORD
- H.pylori treatment
What is the MOA for PPIs?
- irreversibly bind to H+/K+ ATPase in gastric parietal cells
- Inhibits the release of H+ ions
- Reduces production of stomach acid
What are some side effects of PPIs?
- Headache
- GI disturbance
- Hypomagnesaemia
- May cause C.diff infections
Warnings for PPIs?
- May disguise symptoms of gastro-oesophageal cancer (as about red flag symptoms)
- Increased risk of fractures in the elderly - osteoporosis
What drug is omeprazole though to interact with?
Clopidogrel
- It is thought to reduce the antiplatelet effect of clopidogrel by decreasing its activation by cytochrome P450
What is the treatment for H.pylori?
- PPI (omeprazole)
- Amoxicillin
- Clarithromycin
If there is a penicillin allergy give:
- Metronidazole
What is an example of a H2 receptor antagonist?
Ranitidine
What is the MOA of ranitidine?
- Blocks H2 receptors on gastric parietal cells
- Reduces gastric acid production
- However this doesn’t completely suppress gastric acid production (H2 receptors can be stimulated by other pathways)
What is the one advantage of H2 receptor antagonist over PPIs?
- They have a more rapid onset of effect
- Used pre-operatively to reduce symptoms of significant GORD
- Prevents possible aspiration of gastric acid causing pneumonitis
What is an example of a bulk-forming laxative?
Ispaghula husk
What medication can help with short-term diarrhoea?
Loperamide
What are examples of osmotic laxatives?
- Lactulose
- Macrogol
- Phosphate enema
What are the indications of osmotic laxatives?
- Constipation or faecal impaction
- Bowel preparation before surgery
- Hepatic encephalopathy
What is the MOA of osmotic laxatives?
- Osmotic agents pull water form surrounding tissues using osmosis
- They hold water in the stool, main thing its volume
- Stimulates peristalsis
Lactulose is also involved in the reduction of ammonia producing bacteria
What is a specific warning with phosphate enemas?
Electrolyte disturbances
- Should be cautioned in people with heart failure and heart failure
- Glycerol suppositories are less likely to cause electrolyte disturbance
What type of laxative can be prescribed alongside opioid analgesia?
Stimulant laxatives
- Reduces the constipation that opioid analgesia causes
What is the MOA for stimulant laxatives?
- They irritate the intestinal cells causing the intestine to contract
- They also promote water influx to the intestine, which promotes bowel movement
What are examples of stimulant laxatives?
- Senna
- Bisacodyl
- Glycerol suppositories
- Docusate sodium
What advice should be given to patients taking laxatives?
Aim to drink 6-8 glasses of liquid per day
What are examples of anti motility drugs?
- Loperamide
- Codeine phosphate
When should codeine phosphate be used over loperamide?
When both analgesia + treatment of diarrhoea are required
What is the MOA of loperamide?
- Opioid receptor agonist (doesn’t act on the CNS)
- Acts on the mu opioid receptors in the myenteric plexus large intestines
- This reduces propulsive contractions of the gut smooth muscle and increases non-propulsive contractions
- Slows transit and allows greater water absorption
What are the warnings of using loperamide?
1) Acute ulcerative colitis - increases the risk of mega colon and perforation
2) C. Diff colitis - increases the risk of mega colon and perforation
3) Acute bloody diarrhoea - haemolytic uraemic syndrome
What type of medication is metoclopramide?
It is an antiemetic( anti sickness medication)
What are the different antiemetics?
1) Dopamine D2 receptor antagonists - metoclopramide (GI issues,opioids)
2) Histamine H1 receptor antagonists - cyclising, cinnarizine,promethazine ( motion sickness & vertigo)
Serotonin 5-HT3 receptor antagonists - ondansetron, granisetron (general anaesthesia, chemotherapy)
