Gastrointestinal Drugs Flashcards
What are Proton Pump Inhibitors indicated in?
- Peptic Ulcers
- Acid
- Dyspepsia
- H. Pylori
What is the MOA of Proton Pump Inhibitors?
- Irreversibly inhibit H/K-ATPase in gastric parietal cells which reduces gastric acid secretion.
What are the main Side effects of Proton pump Inhibitors:
- GI upset
- Headaches
- Long term = hypomagnesaemia
- osteoporosis
- Increases Gastric pH which may reduce the body’s host against defence.
What are PPIs contraindicated in?
- May disguise symptoms of gastro-oesophageal cancer
- In elderly, can increase risk of fracture due to risk of osteoporosis.
What are the key interactions of Proton Pump Inhibitors?
- Omeprazole can reduce the antiplatelet effect of clopidogrel by decreasing its activation
- Lansoprazole and Pantoprazole have a lower propensity to interact with clopidogrel (thus preferred when prescribing alongside clopidogrel).
What are H2 receptor Antagonists indicated in?
- NSAID-associated ulcers
- Gastric and duodenal ulcers
- Dyspepsia and GORD
What is the MOA of H2 receptor antagonists?
- reduce gastric acid secretion
- Proton pump of gastric parietal cell produces acid by secreting H+ into stomach lumen in exchange for K+, which is regulated by histamine
- Blocks histamine H2-receptors on the gastric parietal cells which inhibits release of H+ by the proton pump, via a 2nd messenger system reduces gastric acid secretion
What are the main sides effects of H2 receptor antagonists?
- Bowel disturbances (diarrhoea and Constipation)
- headaches
- Dizziness
- Hypotension
- dark Urine
- alopecia
whom is H2 receptor antagonists contraindicated in?
- renal impairment (low dose)
- may disguise symptoms of oesophageal cancer.
What are 2 examples of PPIs?
Omeprazole
lanzoprazole
What is an example of H2 receptor antagonist?
- Ranitidine
- (-tidine)
What is an example of an antacid?
- Gaviscon
- Sodium bicarbonate
- Calcium carbonate
What is the main indications of antacids?
- Dyspepsia
- heartburn
- GORD
What is the MOA of antacids?
- alkali to neutralise stomach acid
What are the side effects of antacids:
Diarrhoea, constipation, Flatulence, cramps, nausea, vomitting
What is the MOA of alginates?
- Increase viscosity of stomach contents which reduces the reflux of stomach acid into oesophagus
- After reacting with stomach acid, they form a floating ‘raft’ which separates gastric contents from the gastro-oesophageal junction to prevents mucosal damage
- May also inhibit pepsin production
What are some examples of alginates:
- Magnesium salts
- Aluminium salts
What are the main side effects of each alginate salt?
- Magnesium salts- diarrhoea
- Aluminium salts- constipation
Whom is antacids contraindicated in?
- Compound alginates should not be given with thickened milk preparations to children as it can cause bloating and discomfort
- Na/K containing preparations used with caution in: Fluid overload and Hyperkalaemia (e.g. renal failure)
- Sucrose preparations can worsen hyperglycaemia in diabetic patients
What drugs do Antacids interact with?
- The divalent cations in compound alginates can bind to other drugs which reduces their absorption
To ensure drug is absorbed ensure dose separated by 2 hours with:
- ACE-inhibitors
- Some antibiotics (e.g. tetracyclines, cephalosporins)
- Bisphosphonates
- Digoxin
- Levothyroxine
- PPIs
Increases the alkalinity of urine meaning it can increase excretion of:
- Aspirin
- Lithium
What is Loperamide used for?
- Diarrhoea
- IBS
- viral gastroenteritis
What are the main side effects of Loperamide?
- Constipation
- cramps
- Flatulence
Who is Loperamide contraindicated in?
- acute ulcerative colitis
- acute bloody diarrhoea
What are antiemetics used for?
- treatment of nausea and vomitting.
- prophylaxis
What are the 4 classes of antiemetics?
- H1 receptor antagonist
- D2 receptor antagonist
- 5HT3 receptor antagonist
- Anti-muscarinic
Give an example of a H1 receptor antagonist?
- Cyclizine
Give an example of a D2 receptor antagonist?
Metoclopramide
Give an example of a 5HT3 receptor antagonist?
- Ondansetron
Give an example of an Anti-muscarinic drug?
Hycosine Hydrobromide
What is the MOA of D2 antagonist?
- Acts in the brain and the gut
- Inhibits D2 receptors in the chemoreceptor trigger zone which is responsible for sensing emetogenic substances in the blood, therefore effective in nausea and vomiting caused by CTZ stimulation.
- Prokinetic effect: increases LOS and gastric tone which promotes gastric emptying, then contributes to their antiemetic action in conditions associated with reduced gut motility
What are the main side effects of D2 receptor antagonists?
- diarrhoea
- movement abnormalities/ tremours
- seizures
- low mood
What is Metoclopramide contraindicated in?
- Should not be prescribed for more than 5 days to reduce the risk of extrapyramidal effects
Avoid in:
- Neonates
- Children
- Young adults
- Intestinal obstruction
- Perforation
- Parkinson’s disease
What drugs does D2 receptor antagonists interact with?
- antipsychotics
- dopaminergic agents especially in parkinson’s disease.
What is the MOA of H1 receptor antagonist?
Blocks the H1 receptor and muscarinic Ach receptors which triggers nausea in the brain.
Side effects of H1 receptor antagonists:
- depression
- drowsy
- dry mouth
What is the MOA of Antimuscarinic in IBS:
- reduces motility
- reduces glandular secretions
- reduced sphincter
- causing muscle dilation
What are the 4 types of laxatives?
- Bulk Forming
- Stimulant
- Osmotic
- Feacal Softeners
Name a bulk-forming laxative?
Ispaghula
Name a stimulant laxative:
- Senna
- Bisacodyl
Name a osmotic Laxative:
Lactulose
Name a Feacal Softening Laxative:
Docusate
What is the MOA of bulk forming Laxative:
- retains fluid in the stool causing an increase in feacal mass which triggers peristalsis and soft stools.
What are the indications for bulk-forming laxatives?
- a low faecal mass
Whom are the bulk-forming laxatives contraindicated in?
- elderly and frail
What are the side effects of using bulk-forming laxatives:
- bloating
- flatulence
Which is the most rapid form of laxative?
Stimulant- takes 6-12 hours to work
Faecal softeners- 12-72 hours to work
What is the MOA of stimulant laxatives?
- increases the intestinal motility which via stimulation of nerves via peristalsis.
- Increases water and electrolyte secretion from the colonic mucosa causing an increase in the volume of colonic content and stimulates peristalsis.
What are some side effects of stimulant laxatives?
- cramps
- diarrhoea
- malanosis coli
What is Stimulant laxative indicated in?
A slow transit
What is Osmotic laxative indicated in?
- Pellet stools
Whom is Osmotic laxative contraindicated in?
- IBS
- Constipation
- Faecal impactation
- bowel preparations for procedures
- hepatic encephalopathy
What is the MOA of Osmotic laxative?
- increase in H2O in the large intestine by drawing fluid from body/ retaining the fluid.
What are the common side effects of Osmotic laxatives?
- nausea
- dehydration
- flatulence
- bloating
- cramps
What are Faecal softeners (laxatives) indicated in?
- Hard stools
What is the MOA of Faecal softners?
- Reduces the surface tension of stools to increase penetration of intestinal fluid into the faecal mass
- use alongside another laxative.
What is the side effects of Faecal softeners?
- cramps
- diarrhoea
When is giving laxative to patients contraindicated?
Intestinal obstruction
How do you treat Helicobacter Pylori?
- Omeprazole + Amoxicillin + (Clarithromycin OR Metronidazole) for 7 days
How do you treat C. Difficile:
- Vancomycin 1st line
