Lecture 20 - GI Pharmacology Flashcards
What is the most common location of pain for gastric or duodenal ulcers?
Epigastric pain
What are some symptoms of gastric or peptic ulcerations?
Bleeding
Perforation
Scarring and possible obstruction
What are some risk factors of gastric acid or peptic ulcers?
Early gastric emptying
Imbalance between normal acid levels and feedback
Helicobacter pylori
NSAIDs
Smoking and alcohol delay healing of ulcers.
Why do NSAIDs increase risk of gastric ulceration?
Reduced prostaglandins which normally inhibit the production of gastric acid
What cells produce histamine stimulating gastric acid production?
Enterochromaffin cells
What are the 3 main stimulatory transmitters for gastric acid production?
ACh
Histamine
Gastrin
What is an example of a combined alginates and antacids?
Gaviscon
What is the purpose of antacids and alginates?
Antacids = buffering stomach acid
Alginic acid = inc stomach content viscosity and reduce reflux
What is contained in gaviscon?
Alginic acid = sodium alginate
Antacids = aluminium hydroxide/magnesium carbonate
What are the adverse effects of magnesium salt and then aluminium salts used as antacids?
Mg salts = diarrhoea
Aluminium salts = constipation
AC
MD
Why are aluminium hydroxide. And magnesium carbonate both taken at the same time if they are both antacids?
Mg salts cause diarrhoea and Aluminium salts can cause constipation
So balance the side effects
What are the warnings and contraindications to alginates and antacids?
Na+ and K+ containing preparations should be carefully used in renal failure
High conc sucrose in some solutions so be careful with hyperglycaemia in DM
What are the important drug drug interactions of alginates and antacids?
Reduce absorption of many drugs
Can inc urine alkalinity increasing aspirin excretion
What are some proton pump inhibtors?
Omeprazole
Lansoprazole
What is the mechanism of action of proton pump inhibitors like omeprazole and lansoprazole?
Why are they so effective?
Irreversibly inhibit the H+/K+ ATPase in gastric parietal cells
Inhibit the final stage in stomach acid production
What are some adverse effects of proton pump inhibtors like omeprazole and lansoprazole?
GI disturbance (abdominal pain, constipation, diarrhoea)
Headache , dizziness
Drowsiness/confusion
What are some warnings and contraindications of proton pump inhibitors?
Mask symptoms of gastro-oesophageal cancer
Osteoporosis - fracture risk
What are some importnat drug drugs interactions of omeprazole?
CYP inhibitor so omeprazole reduces clopidogrel activation
PPIs can increase effects of warfarin and phenytoin
What are PPIIs often prescribed alongside with?
NSAID
Steroid
What is an example of H2 receptor antagonists?
Famotidine
How do H2 receptor antagonists work?
(Famotidine)
Inhibts H2 receptors since histamine release contributes to proton pump. Activation
How do H2 receptor anatagonists like Famotidine compare in their action to proton pump inhibtors like omeprazole and lansoprazole?
PPIs act at the final step of acid production so are very effective
H2 receptor antagonists dont act as far down the pathway so only partially reduce acid secretion
What are the adverse effects of Famotidine? (H2 receptor antagonists)
Generally well tolerated
Diarrhoea
Headache
What are the warnings/contrainidactions of Famotidine? (H2 receptor antagonists)
Mask symptoms of gastro-oesophageal cancers
Renal impairment
What are the DDIs of Famotidine? (H2 receptor antagonists)
Very few
When should Helicobacter pylori infection be suspected?
Duodenal or gastric ulcerations
What test is used to determine a Helicobacter pylori infection?
Urea breath test
Breath in C13 and H-pylori will convert urea to ammonia and ammooonia will be breathed out containing C13
How is Helicobacter pylori infection treated?
One week triple therapy
PPI + 2 anti bacterial agents
What mediations are given for Helicobacter pylori infection?
Lansoprazole + Clarithromycin + Amoxicillin
Lansoprazole + Clarithromycin + Metronidazole (when allergic to penicillin)
What are some examples of aminosalicylates?
Mesalazine
Sulfalazine
What is the first line treatment for ulcerative colitis?
Mesalazine
What is the mechanism of action of Mesalazine in ulcerative colitis?
Enteric coated tablet limits gastric breakdown leading to release of 5-amino salicylic acid topical action at the colon
Why does Mesalazine not work in rheumatoid arthritis but sulfasalazine does?
Sulfa group good for RA
What are the adverse effects of aminosalicylates (Mesalazine)?
GI disturbance (nausea and dyspepsia)
Leukopenia (rare)
What are the warning/contraindications to Mesalazine (aminosalicylates)?
They’re like aspirin so may have similar hypersensitivity to them
What aer some DDI for Mesalazine (aminosalicylates)?
Using PPIs may lead to the enteric coated tablets breaking down quicker due to. Increased PH
