GI examination - Peptic ulcers, laxatives, constipators

Question 1

What is the mechanism of action of omeprazole?

Answer 1

 Prevents H+ ions being pumped into parietal cell canaliculi by targeting ATPase
 Only works if you eat (you need proton pumps working for it to bind)

Question 2

What is the mechanism of action of histamine

Answer 2

Cimetidine

 Removes the amplification of Gastrin/Ach signal by acting as a Histamine Receptor Antagonist

Question 3

How do you treat Gord?

Answer 3

o Lifestyle
o Antacids
o H2 Receptor Antagonists
o PPI

Question 4

Give four adverse reactions to PPIs

Answer 4

o GI upset
o Nausea
o Headaches
o Risk of gastric atrophy with long-term treatment

Question 5

Give four H2 receptor antagonists

Answer 5

o Dizziness
o Fatigue
o Gynaecomastia
o Rash

Question 6

What is h.Pylori triple therapy

Answer 6

PAC
Proton pump inhibitor
Two antibiotics - Amoxicillin/Clarithromycin

Question 7

When are PPIs used?

Answer 7

 Short term treatment of peptic ulcers
 Severe GORD
 Confirmed oesophagitis
 Eradication of H. Pylori (part of triple therapy)
 Zollinger-Ellison Syndrome (Gastrin secreting pancreatic tumour)

Question 8

What is the mechanism of action of PPI?

Answer 8

 Irreversibly inhibit Na/K-ATPase that is responsible for proton secretion from parietal cells.

Question 9

Give the main ADRs associated with PPI

Answer 9

GI upset, nausea
Headaches
Gastric atrophy

Question 10

Give a key DDI of omeprazole

Answer 10

 Omeprazole is a CYP450 enzyme inhibitor

 Avoid use with patients being treated with Warfarin, Phenytoin etc.

Question 11

How long do PPI take to work?

Answer 11

PPI action is delayed as not all pups are active all of the time. Maximum efficacy is after 2-3 days and only works if you eat as existing acid has to be pumped out into intestine.

Question 12

What are the two indications for H2 antagonists?

Answer 12

Peptic ulcer disease and GORD

Question 13

How do H2 antagonists work?

Answer 13

 Competitively antagonist H2 receptors, blocking the amplifying action of Histamine on Parietal cells

Question 14

What are four key ADRs for H2 antagonists?

Answer 14

 Dizziness
 Fatigue
 Gynaecomastia
 Rash

Question 15

What is a key DDI of H2 antagonists?

Answer 15

 Cimetidine is a CYP450 enzyme inhibitor

 Avoid use with patients being treated with Warfarin, Phenytoin etc

Question 16

When are H2 antagonists given?

Answer 16

At night when food buffering at lowest

Question 17

Name four types of laxative

Answer 17

Bulk laxatives
Faecal softeners
Osmotic laxatives
Stimulant laxative

Question 18

When would you give bulk laxative?

Answer 18

Constipation

Question 19

What is the mechanism of action of bulk laxatives

Answer 19

Increases the volume of non-absorbable solid residue in the gut , distending the colon and stimulating peristaltic movements

Question 20

When should you not use a bulk lax?

Answer 20

 Dysphagia
 Intestinal obstruction (Adhesions, ulceration)
 Colonic atony
 Faecal impaction

Question 21

What are three adverse reactions to bulk laxatives?

Answer 21

 Flatulence
 Abdominal distension
 GI obstruction

Question 22

Name an osmotic laxative

Answer 22

Lactulose

Question 23

What is the mechanism of action of osmotic laxatives

Answer 23

 Increase water content of the bowel via osmosis
 Lactulose – Disaccharide (galactose/fructose) that cannot be hydrolysed by digestive enzymes. The fermentation of lactulose by colonic bacteria gives acetic and lactic acid. This has an osmotic effect

Question 24

When should you not use osmotic laxative?

Answer 24

Constipation

Question 25

Give four ADRs of osmotic laxatives

Answer 25

 Flatulence
 Cramps
 Abdominal discomfort
 Caution required to prevent intestinal obstruction

Question 26

Give an anti-diarrhoeal

Answer 26

Codeine

Question 27

When should anti-diarrhoeals NOT be used

Answer 27

Inflammatory bowel disease - Toxic mega colon

Question 28

What is the mechanism of action of codeine anti-diarrhoeals

Answer 28

 Act on opioid receptors in the bowel
 Reduce motility (increase time for fluid reabsorption)
 Increase anal tone and reduce sensory defecation reflex

Question 29

Anti-diarrhoeals adverse reactions (5)

Answer 29

 Nausea, vomiting, abdominal cramps, constipation drowsiness

Question 30

What is one anti-diarrhoeal with super good morphine effects`

Answer 30

Imodium, can’t penetrate BBB, super effective

Question 31

How do bulk forming anti-diarrhoeals work?

Answer 31

Relatively small amount of faecal fluid influences composition.

Question 32

What is IBS?

Answer 32

Chronic:
o	Abdominal Pain
o	Discomfort
o	Bloating
o	Alteration of Bowel Habits

Question 33

Give process of vomiting

Answer 33

o Pyloric sphincter closes while the cardia and oesophagus relax
o Gastric contents propelled by contraction of abdominal wall and diaphragm
o Glottis closes with elevation of soft palate, preventing entry of vomit into the trachea and Nasopharynx
 If vomiting is due to alcohol, or patient has a cranial nerve lesion they are at a higher risk of aspiration as this does not work properly

Question 34

Give 3 types of anti-emetics

Answer 34

Dopamine receptor antagonist
Serotonin antagonist
Muscarinic receptor antagonist

Question 35

What is the mechanism of action of vomtiing

Answer 35

Things (medication, smell, touch, raised ICP, stomach) stimulate postrema on floor of 4th ventricle
Vestibular apparatus disturbance
Both stimulate medullary centre, whcih releases aCh, histamine and serotonin, which causes vomiting

Question 36

How do dopamine receptor antagonists work?

Answer 36

 Acts on the Postrema on the floor of the 4th ventricle

 Acts on the stomach to increase the rate of gastric emptying

Question 37

What are three ADRs of dopamine receptor antagonists

Answer 37

 Stimulates prolactin release
 Metoclopramide – extra-pyramidal reactions (dystonia) occur in 1%, therefore is avoided in Parkinson’s disease
 Galactorrhoea – Can induce pro-lactin

Question 38

What is the mechanism of action of serotonin antagonists?

Answer 38

 5-HT is released into the gut, reducing Vagus activity, therefore effective at deactivating the vomiting centre (the Postrema on the floor of the 4th ventricle)
 Blocks Serotonin receptors in Chemoreceptor Trigger Zone

Question 39

What are three ADRs of serotonin antangonists

Answer 39

 Headaches, constipation, flushing