Gastrointestinal Drugs Flashcards
Describe how to reduce acid secretion in the stomach. (5)
Target the parietal cell: M3 ACh receptors H2 histamine receptor (key) CCKB Gastrin receptor Direct cavalry stimulation
Describe H2 receptor antagonists.
MoA (2)
Pharmacokinetics. (2)
ADRs (1)
Inhibits histaminergic stimulation of parietal cells to reduce acid output.
t1/2 of 6-8 hours, so needs to be given bd.
Loose stools.
Give an example of a H2 antagonist. (1)
Ranitidine.
Describe proton pump inhibitors.
MoA (4)
Reversal (2)
Health concerns. (5)
Binds in its active state to active pumps (pumps only active after eating, so needs to be taken before food) to prevent secretion of H+. Takes 3-5 cycles to reduce acid production.
Once ceased, acid secretion returns in 2-3 days.
High Gastrin seen here (trying to prompt the parietal cells) was though to be harmful like in Zollinger-Ellison, but it’s not. Also associated with osteoporosis in long term use (affects calcium absorption).
Describe Zollinger-Ellison Syndrome. (2)
A gastrinoma (Gastrin secreting tumour) leading to high gastrin, and so high acid secretion.
Name three PPIs. (3)
Give the common feature of the names of PPIs. (1)
Lansoprazole, omeprazole, esomeprazole.
-prazole
Describe the initial treatments for peptic disease that are available OTC. (6)
Antacids - bicarbonate Lifestyle changes - weight loss, diet Alginates - gaviscon - forms a viscous layer over the exposed mucosa to stop irritation. H2 receptor antagonists PPIs
Describe the treatment plan of a patient with peptic ulceration. (4)
Explain the low compliance of this plan. (1)
Stop NSAIDs Begin H. Pylori eradication: Clarithromycin Amoxicillin Lansoprazole Over 100 tablets in a day.
Explain the differences between regurgitation and vomiting. (4)
Vomiting is Involuntary, and forceful expulsion of gastric contents, regurgitation is effortless and relating to a problem of the LOS closing.
Describe the stages in vomiting (8)
CTZ in the medulla signals to vomit Nausea, sweating, salivation occur during intestinal reverse peristalsis. Deep inspiration Closure of glottis Abdominal muscles contract Lower oesophageal sphincter relaxes Vomiting occurs.
Describe the types of things that can trigger the chemoreceptor trigger zone (CTZ) and give an example of each type. ((8)
Sensory afferent via the midbrain eg a bad smell
Direct triggers eg drugs, hormones, toxins
Visceral afferent from gut eg stretch in obstruction
Vestibular nuclei eg in motion sickness.
Name two drugs acting primarily on the vestibular nuclei. (2)
Hyoscine hydrobromide
Cyclizine
Describe Hyosine Hydrobromide.
MoA (2)
Uses (3)
Side effects (4)
Muscarinic receptor competitive antagonist - blocks body wide ACh.
Used in motion sickness and bowel obstruction (reduced GI secretions is good)
Side effects: sedation, dry mouth, constipation, glaucoma.
Describe Cyclizine.
MoA (2)
Uses (3)
Side effects (4)
H1 receptor antagonists - antihistamines
Used to reduce motion sickness, help you sleep (drowsiness), reduce allergic reactions.
Side effects: drowsiness, antimuscarinic effects (dry mouth, constipation, urinary retention), and long QT syndrome.
Name three drugs that act primarily on the visceral gut afferents. (3)
Ondansetron
Metaclopramide
Domperidone
Describe Ondansetron.
MoA (3)
Side effects (4)
5HT3 (seratonin) receptor antagonist that reduces GI motility and GI secretions
Side effects are rare but can include constipation, headache, long QT syndrome, deranged LFTs, Parkinsonism.
Describe metaclopramide.
MoA (4)
Uses (2)
Side effects (3)
D2 receptor antagonists - increased ACh at muscarinic receptors - promotes gastric emptying and increases peristalsis.
Good in GORD or ileus.
Side effects include galactorrhoea, dystonia and Parkinsonism.
Describe domperidone.
MoA (1)
Uses (1)
Side effects (2)
D2 receptor antagonist used to improve lactation in breastfeeding mothers.
Side effects include sudden cardiac death (long QT and VT) and severe galactorrhoea.
Name four drugs that act only on the CTZ. (4)
Haloperidol
Prochlorperazine (“the zines”)
Dexamethosone
Aprepitant
Describe Haloperidol.
MoA (1)
Uses (4)
Side effects (4)
D2 receptor antagonist
An antipsychotic useful as an antiemetic in chemo and palliation. Consider especially in hypotension.
Side effects include dystonia, Parkinsonism, sedation and hypertension.
Describe prochlorperazine.
MoA (1)
Use (2)
Give another example of a drug in this class. (1)
A D2 receptor antagonist.
An antipsychotic that is also used as an antiemetic. Especially safe in pregnancy.
Promethazine.
Describe dexamethasone. Class (1) MoA (2) Uses (4) Side effects (3)
Corticosteriods
Acts directly on the CTZ but also antagonises D2 receptors.
Perioperative N+V, palliation, chemo; consider especially in malnutrition.
Side effects include insomnia, increased appetite, increased blood sugar.
Describe aprepitant.
MoA (3)
Uses (2)
Side effects (4)
Neurokinin 1 receptor antagonist that prevents the action of substance P at the CTZ and in peripheral nerves.
Used often in chemo because has anxiolytics and antidepressant properties.
Side effects include headache, diarrhoea or constipation, Stevens-Johnson Syndrome (extreme skin reaction).
Name an example of a neurokinin 1 receptor antagonist. (1)
Give the common feature of the names of these. (1)
Aprepitant.
-pitant
Explain why aprepitant and ondansetron are commonly prescribed together. (2)
Because aprepitant boosts effectiveness of 5HT3 receptor antagonists (like ondansetron) - given together.
Describe the first line prescription option in regards to motion sickness. (2)
Hyoscine hydrobromide is first line, but this is sedating.
Describe the treatment options with unknown cause but severe vomiting. (8)
Consider a nasogastric tube - can remove the need to vomit because stomach doesn’t cycle between full and empty. Use prokinetics (like domperidone) for GORD or ileus, but not if obstruction or risk of perforation suspected. Ondansetron +/- Cyclizine then add dexamethasone if no better.
Describe the treatment options in hyperemesis gravidum. (5)
Avoid drugs if can.
Promethazine or prochlorperazine.
Add methaclopramide
Add ondansetron.
Describe the treatment of chemotherapy related emesis. (6)
If low risk - dexamethasone (corticosteriods)
If medium risk - dexamethasone (corticosteriods) and ondansetron (5HT3 receptor antagonist).
If high risk - dexamethasone (corticosteriods), ondansetron (5HT3 receptor antagonist) and aprepitant (NK1 antagonist).
For emergency rescue in all risk levels - metaclopramide (D2 receptor antagonist).
Describe the risk factors for post operative nausea and vomiting. (9)
Patient - female, non-smoker, young, history of PON+V/motion sickness.
Anaesthetic - general, opioid use, anaesthetic mix.
Surgery - longer operation, laparoscopic.
Describe the treatments of post operative nausea and vomiting. (2)
Wait and see Add in antiemetics of each class until something works.
Define diarrhoea. (2)
A change in stool consisetancy or frequency from the patients normal.
Describe loperamide.
MoA (5)
An opioid receptor antagonist specific to the mew receptors in the myenteric plexus.
Decreases muscle tone and reduces peristalsis.
Describe the use of codeine and morphine to treat diarrhoea.
MoA (1)
Use (1)
Side effects (3)
More generalised mew opioid receptor antagonist.
Consider if patients have diarrhoea and pain.
Side effects include paralytic ileus, N+V, sedation, addiction.
Describe the constipating diet as a treatment for diarrhoea. (5)
For those with long term loose stool - IBS, IBD, drugs.
Limits fibre to just enough, avoids fizzy drinks and caffeine, considers probiotics.
Define constipation. (2)
An increase in hardness or a decrease in frequency from the patients normal.
Describe lifestyle changes that can be made to reduce constipation. (4)
Drink more water
Increase fibre intake
Regular exercise
Toilet routine and positioning
Describe laculose.
MoA (2)
An osmotic laxative that draws fluid into the large bowel.
Describe movicol.
Class (1)
MoA (3)
A macrogol.
As osmotic laxative that retain the fluid that it came in with - needs to be taken with a big drink of fluid.
Describe senna.
MoA (2)
Administration options (2)
Stimulant laxative that increases the motility of the gut.
Can be oral or PR.
Describe docussate sodium.
MoA (4)
Administration. (2)
A stimulant laxative that increases the motility of the gut, and a stool softener that decreases surface tension.
Can be oral or PR.
Describe how fibre can act as a laxative. (W)
“Bulk forming” to increase ease.
Describe how fibre can act as a laxative. (2)
“Bulk forming” to increase ease.
Define a high output stoma. (2)
Over 1.5l out in 48 hours.
Describe one treatment for a high output stoma. (3)
Octreotide
Somatostatin analogue that reduces GI secretions.
