Pharmacology

Question 1

What is the process of HCl secretion?

Answer 1

CO2 and water are converted to carbonic acid by carbonic anhydrase
HCO3 and H+ are also produced
HCO3 is pumped out fo the cell into the blood in exchange for Cl, which is pumped into the lumen
H+ is pumped into he lumen in exchange for K+ by the proton pump (H/K/ATPase)
H+ and Cl make HCl

Question 2

Via which receptors do secretagogues cause secretion?

Answer 2

M3 muscarinic
G/CCK2
H2

Question 3

What is the process that causes HCl secretion via M3 receptors?

Answer 3

ACh binds to receptor
Cause increased cAMP
Increases number of proton pumps
Increases acid secretion

Question 4

What is the process that causes HCl secretion via G/CCK2 receptors?

Answer 4

Gastrin binds to receptor
Causes increase in intracellular calcium
Increases number of proton pumps
Increases acid secretion

Question 5

What is the process that causes HCl secretion via H2 receptors?

Answer 5

Histamine from enterochromaffin cells binds to receptor
Increases cAMP
Increases number of proton pumps
Increases acid secretion

Question 6

What is the mechanism of PPIs?

Answer 6

Irreversible inhibit proton pumps so H+ cannot be pumped into lumen, decreasing acid secretion

Question 7

Where do PPIs not work, and what should be done to counter this?

Answer 7

In tubulovesicle proton pumps

Take 20 mins before eating because that is the time taken for proton pumps to move to the canalicular membrane

Question 8

What are examples of PPIs?

Answer 8

Omeprazole

Lansoprazole

Question 9

What are the side effects of PPIs?

Answer 9

Increased risk of infection, e.g. C. diff

Osteoporosis

Question 10

What is the mechanism of H2 receptor antagonists?

Answer 10

Blocks H2 receptor so histamine cannot act on parietal cell to decrease acid production

Question 11

How do H2 receptor antagonists compare to PPIs in terms of effectiveness, and why?

Answer 11

Less effective

H2 blocked but ACh and gastrin can still cause acid secretion

Question 12

When are H2 receptor antagonists used?

Answer 12

If PPIs contraindicated, or not receptive to PPIs

Question 13

What are examples of H2 receptor antagonists?

Answer 13

Ranitidine
Cimetidine
Famotidine
Nizatidine

Question 14

What are the side effects of H2 receptors antagonists?

Answer 14

Masks symptoms of gastric malignancy

Question 15

What is the mechanism of antacids?

Answer 15

Buffer HCl and make pH in the stomach more neutral

Question 16

What is the mechanism of alginates?

Answer 16

Increase the viscosity of gastric juice and react with acid to produce a foam later that protects the oesophagus

Question 17

What is the indication for antacid alginate combination?

Answer 17

OTC for short term symptomatic relief

Question 18

What are examples of compound alginates?

Answer 18

Peptac
Gaviscon
Mucogel (antacid only)

Question 19

What is the function of prostaglandins and somatostatin?

Answer 19

They reduce the effect of secretagogues and inhibit gastric acid secretion

Question 20

What is the mechanism of NSAIDs?

Answer 20

Inhibit COX1
This causes decreased prostaglandins production
Less prostaglandins means more acid secretion

Question 21

What are examples of NSAIDs?

Answer 21

Aspirin
Ibuprofen
Diclofenac
Naxaproxen

Question 22

What is misoprostol, and what is its indication?

Answer 22

Prostaglandin agonist - prescribe at the same time as NSAIDs to prevent adverse effects and reduce the risk of ulcer

Question 23

What is the pathology that causes diarrhoea?

Answer 23

Increased solutes in the lumen - water follows

Question 24

What class of drug are synthetic opioids?

Answer 24

Anti-motility so also anti-diarrhoeal

Question 25

What is the mechanism of synthetic opioids?

Answer 25

Opioid agonists Inhibit ENS to decrease peristalsis and increase segmentation Increase fluid absorption

Question 26

What are the examples of synthetic opioids?

Answer 26

Loperamide (imodium) - used most often | Codeine phosphate

Question 27

What are the contraindications for synthetic opioids?

Answer 27

``` (ABCD) Acute UC Babies C. Diff colitis Dysentery (or any bloody diarrhoea) ```

Question 28

What is the mechanism of rehydration therapy?

Answer 28

Na and glucose in the rehydration salts is absorbed by SGLT1 | Water follows and is absorbed too

Question 29

What are causes of constipation?

Answer 29

Lack of fibre Lack of physical activity Drugs (e.g. opioids) Obstruction

Question 30

What is the mechanism of bulking laxatives?

Answer 30

Indigestible so add to faecal mass and cause the stool to absorb water Increase the bulk of stool so peristalsis is stimulated

Question 31

What are examples of bulking laxatives?

Answer 31

Ispaghula husk Methylcellulose Sterculia

Question 32

What are the contraindications for bulking laxatives?

Answer 32

Bowel obstruction | Ileus

Question 33

What is the mechanism of osmotic laxatives?

Answer 33

Cause osmosis, water travels into stool | Increase in bulk, peristalsis activated

Question 34

What are examples of osmotic laxatives?

Answer 34

Lactulose | Macrogols

Question 35

What are contraindications for osmotic laxatives?

Answer 35

Bowel obstruction | Heart failure, ascites, electrolyte disturbances

Question 36

What is the mechanism of stimulant laxatives?

Answer 36

Stimulate intestinal motility and water secretion into lumen | Stimulate enteric nerves

Question 37

What are examples of stimulant laxatives?

Answer 37

Senna | Glycerol suppository

Question 38

What are the contraindications of stimulant laxatives?

Answer 38

Bowel obstruction | Prolonged use

Question 39

What are the side effects of stimulant laxatives?

Answer 39

Abdominal pain

Question 40

What is nausea?

Answer 40

Unpleasant sinking feeling hit throat or stomach Involves pallor, sweating, salivation Stomach and LOS are relaxes

Question 41

What is retching?

Answer 41

Rhythmic reverse peristalsis Involuntary abdominal and diaphragm contraction No gastric content expelled

Question 42

What is emesis?

Answer 42

Forceful expulsion of gastric/intestinal contents out of mouth

Question 43

What are the events of vomiting?

Answer 43

1. Intestinal slow wave activity stops 2. Retrograde contraction from ileum to stomach 3. Glossitis is closed and breathing stops to prevent aspiration 4. LOS relaxes 5. Diaphragm and abdominal muscles contract 6. Gastric contents ejected

Question 44

What can iatrogenic vomiting be caused by?

Answer 44

Chemotherapy General anaesthetic Drugs, e.g. morphine and SSRIs Post-op

Question 45

What are the consequences of vomiting?

Answer 45

Dehydration Loss of gastric protons and chloride causing metabolic alkalosis and can lead to hypokalaemia Oesophageal damage

Question 46

What are examples of anti-emetics?

Answer 46

5-HT3 antagonists Muscarinic acetylcholine Histamine H1 antagonists Dopamine receptor antagonists

Question 47

What is the mechanism of 5-HT3 antagonists, what is an example, and what are they used for?

Answer 47

Block 5-HT3 receptors to reduce vomiting in the vomiting centre Ondansetron Nausea due to chemo

Question 48

What is the mechanism of muscarinic acetylcholines, what is an example, and what are they used for?

Answer 48

Unclear Hyoscine, scopolamine Proplylaxis of motion sickness

Question 49

What is the mechanism of histamine H1 antagonists, what is an example, and what are they used for?

Answer 49

Blocks H1 in the vestibular nuclei Cyclizine Proplylaxis of nausea due to inner ear pathology

Question 50

What is the mechanism of dopamine receptor antagonists, what is an example, and what are they used for?

Answer 50

Block dopamine system, are pro-kinetic Domperidone, metoclopramide Drug induced vomiting

Question 51

What is an example of an indication for metoclopramide?

Answer 51

With morphine in MONA+T acute heart attack management