Gastrointestinal Drugs Flashcards
Name some Proton Pump Inhibitors
Omeprazole, Lansoprazole, Rabeprazole, Esomeprazole and Pantoprazole
When are PPI’s used?
In treatment of GORD, PUD and Zellinger-Ellison Syndrome
How do PPI’s work?
Irreversible inhibition of H+/K+ATPase at parietal cells, decreasing secretion of acid into the stomach.
What are some ADRs of PPI use?
GI upset, headache and gastric atrophy.
Name some Histamine Receptor Antagonists
Cimetidine and Ranitidine
How do Histamine Receptor Antagonists work?
Antagonise H2 receptors, preventing amplification of parietal cell stimulation, reducing acid output into the stomach.
What are some ADRs of Histamine Receptor Antagonists?
Dizziness, fatigue, gynaecomastia and rash.
When are Histamine Receptor Antagonists best taken?
At night, as there is less food to buffer stomach acid, worsening GORD/PUD.
Name some Oral Bulk Laxatives
Ispaghula, Bran and Methylcellulose
When are bulk laxatives used?
For constipation with hard faeces
What are contraindications for bulk laxative use?
Dysphagia, intestinal obstruction or ulceration, colonic atony, faecal impaction.
What is the mechanism of action for bulk laxatives?
Increase volume of non-absorbable residue in the gut, stimulating gut wall stretch receptors, increasing peristalsis.
What are ADRs of bulk laxatives?
Flatulence, abdominal distension, and gastrointestinal obstruction.
Name some Faecal Softeners and how they are given?
Arachis Oil, as an enema, and Glycerol, given as a rectal suppository.
What are faecal softeners used for?
Haemorrhoids, constipation, faecal impaction, and anal fissures.
What are contraindications for faecal softener use?
Age below 3 years.
What is the mechanism of action faecal softeners?
Lubricate and soften stool.
Name some osmotic laxatives and their method of administration
Lactulose (oral), Magnesium and Sodium salts (rectal) and Movial (oral powder).
When are osmotic laxatives used?
For hard faecal constipation.
What is the mechanism of action for osmotic laxatives?
Increase osmosis and water movement into the bowel lumen. Specifically in Lactuloses case, lactulose is fermented by gut flora to acetic and lactic acid, having an osmotic effect.
What are ADRs for osmotic laxatives?
Flatulence, cramps, abdominal discomfort and intestinal obstruction.
When specifically are Magnesium and Sodium Salts used?
For rapid relief of severe constipation.
When are irritant/stimulant Laxatives used?
For soft faecal clearance before operations or medical procedures.
What are some examples of irritant/stimulant laxatives?
Senna, Danthron, and Bisacodyl
What is a contraindication for irritant/stimulant laxative use?
Intestinal obstruction
What is the mechanism of action for irritant/stimulant laxative use?
Increase GI peristalsis and water/electrolyte secretion from the mucosa.
What are ADRs of irritant/stimulant laxatives?
Hypokalaemia and Colonic Atony
Name some oral Anti-motility Antidiarrhoeals
Codeine and Imodium
How do Codeine and Imodium work?
Act as opioid receptor agonsts, which decrease colonic motility and increase anal tone.
What are contraindications for codeine or imodium use?
Toxic Megacolon (in IBD)
What are ADRs for codeine or imodium?
Constipation, drowsiness and abdominal cramps.
What is an example of a bulk forming antidiarrhoeal and when is it used?
Ispaghula, and used in IBS or ileostomy patients.
What is a contraindication for bulk forming antidiarrhoeal use?
Intestinal obstruction
How do bulk forming antidiarrhoeals work?
Absorb faecal fluid.
When is mebeverine used and how does it work?
Decreases colonic hypermotility, to treat symptoms of Irritable Bowel Syndrome
What type of drugs can be used as anti-emetics?
Dopamine D2 Receptor Antagonists, Serotonin Antagonists, Anti-muscarinics, Histamine H1 Receptor Antagonists, cannabinoids (nabilone) and benzodiazapines.
Hoiw do Dopamine Antagonists work?
Act on the postrema of 4th ventricle floor (vomiting centre), and increase the rate of stomach emptying.
Name some dopamine antagonists used in antiemesis
Domperidone, Metoclopremide
What is an ADR of dopamine antagonist use?
Prolactin release, Extra-pyramidal dystonia
What serotonin antagonists can be used for anti-emesis?
Ondansetron, Granisetron
When are serotonin antagonists likely to be used?
For post-op, chemoptherapy and radiotherapy.
What is the mechanism of action for serotonin antagonists?
Deactivate the vomiting centre, and decrease vagus nerve activity.
What are ADRs of serotonin antagonist use?
Constipation, flushing and headache.
What Anti-muscarinic (M1 antagonist) can be used, and when is it likely to be used?
Hyoscine, and used for motion sickness.
What ADRs can arise from Hyoscine use?
Bradycardia, dry mouth, dyshydrosis
What Histamine (H1) antagonist is likely to be used for anti-emesis?
Cyclizine or Phenothiazine
What contraindication exists for cyclizine?
Any history of myocardial ischaemia.
What ADRs occur from cyclizine?
Sedation and QT prolongation.
