GIT - gastritis

Question 1

Agents that reduce gastric acidity

Answer 1

Antacids (anti-acid): neutralise acid
H2 receptor antagonist: famotidine
Proton pump inhibitors (PPI): omeprazole

Question 2

Mucosal protective agents

Answer 2

Sulcralfate
Misoprostol
Bismuth

Question 3

Agents that eradicate H pylori

Answer 3

Clarithromycin
Amoxicillin
Omeprazole

Question 4

Factors cause PUD (peptic ulcer disease)

Answer 4

Increase damage: H.pylori, NSAID, Aspirin, Cigarettes, Alcohol, Gastric hyperacidity, Duodenal-gastric reflux
Impaired defence: Ischemia, shock, delayed gastric emptying

Question 5

Antacids: 4 examples + arrange in rate of neutralisation

Answer 5

NaHCO3 > CaCO3 > MG(OH)2 > Al(OH)3

Question 6

Products of antacid + side effects

Answer 6

form H2O + salt
NaHCO3: produce CO2 (also metabolic acidosis)
feeling of bloatedness (flatulence), belching, abdominal discomfort
Na+ and Ca2+ retention = fluid retention, hypercalcemia
metabolic alkalosis
affects absorption of other drugs - 2hrs gap**
RENAL CLEARANCE

Question 7

what comes with antacids to reduce ADR

Answer 7

simethicone - anti-foaming agent

helps to release the gas through burping

Question 8

Mg(OH)2 ADR

Answer 8

MG2+ : gives osmotic diarrhoea (effect cancels out when given with Al3+

Question 9

Al(OH)3 ADR

Answer 9

Al3+ : gives constipation (effect cancels out when given with Mg2+

Question 10

H2 receptor antagonists mechanism of action

Answer 10

1. competitive inhibitors of H2 (histamine) receptors on parietal cells -> suppress gastric secretion
2. block amplification of gastrin + cholinergic signals through ECL cells (in gastric mucosa) - makes it potent

Question 11

H2 antagonist drugs

Answer 11

-tidine
famotidine - most potent, but safe
cimetidine
ranitidine

Question 12

cimetidine ADR

Answer 12

inhibit cytochrome p450 = decrease metabolism of other drugs
mental confusion
anti-androgenic effects: males - gynaecomastia, females - galactorrhea (nipple discharge)

Question 13

PPI MOA

Answer 13

protonated in gastric lumen, forming thiophilic sulphenamide
concentrated in parietal cell canaliculi
irreversibly inhibit H+/K+ATPase in parietal cells - by forming covalent disulphide bonds -> increase pH -> less favourable for pathogens to grow
+ direct anti-microbial activity against H.pylori

Question 14

PPI 2 drugs

Answer 14

-prazole
omeprazole** -> most potent gastric acid inhibitor!!
esomeprazole

Question 15

are PPIs active?

Answer 15

inactive prodrug
tablet covered by coating so that it will not be activated before reaching - activated drug is not able to be absorbed
SI

Question 16

how to take PPIs

Answer 16

bioavailibity decreased by 50% when taken with food = need to be taken on an empty stomach - 1hr before breakfast
+ need to be present during meal time (when proton pumps are active) - 1hr half life
(proton pumps activated better with a high protein meal - meat)

takes 3-4 days to fully inhibit gastric acid secretion, continue taking for 4-6wks
high efficacy

Question 17

PPI ADR

Answer 17

generally quite safe
Ca def -> osteoporosis
headache, diarrhoea, nausea, constipation, flatulence

Question 18

3 agents for gastric mucosal protection

Answer 18

sucralfate
bismuth compounds
misoprostol

Question 19

sucralfate MOA

Answer 19

sulphate (-ve charge) binds to +ve charge proteins at the ulcer, forms viscous, tenacious gel preventing further acid attack
stimulates mucosal prostaglandin and bicarbonate secretion

Question 20

how to take sucralfate + used for what circumstances

Answer 20

empty stomach - 1hr before meals
prevention of stress-related bleeding in critically ill patients
not used for ulcers - use H2 antagonist and PPI

Question 21

sucralfate ADR

Answer 21

constipation

impairs other drug absorption

Question 22

Bismuth MOA

Answer 22

forms a protective layer protecting ulcers from acid and pepsin
Stimulates mucus and bicarbonate secretion
Directly anti-microbial activity against H. pylori

Question 23

Bismuth: used under what circumstances

Answer 23

dyspepsia (indigestion)
acute diarrhoea
eradication of H pylori (quadruple therapy: PPI + metronidazole + tetracycline + bismuth subcitrate)

Question 24

Bismuth: what to take note

Answer 24

generally safe for short term
prolonged use may cause bismuth toxicity -> encephalopathy
warn patients of harmless blackening of stool and reversible darkening of tongue
avoid in RENAL patients

Question 25

misoprostol usage

Answer 25

rapidly absorbed - short T1/2 - 4 times per day

Prevention of NSAID-induced peptic ulcers

Question 26

misoprostol MOA

Answer 26

(mimics prostaglandin)
Binds to PGE2 receptors
At low dose (cytoprotective): promotes bicarbonate and mucus secretion, enhances mucosal blood flow
At high dose (antisecretory): inhibits gastric acid secretion

Question 27

misoprostol ADR

Answer 27

Abdominal pain
Diarrhoea
Abortion (uterine contraction) -> ppl may use as abortifacient
Bone pain and hyperostosis 
(excessive bone growth)
not really used nowadays

Question 28

Eradication of H.Pylori

Answer 28

1st line: triple therapy (2 antibiotics + 1 PPI)
- Clarithromycin
- Amoxicillin/ Metronidazole
2 antibiotics given tgt to prevent buildup of resistance
- Anti-secretory agent (PPI): Omeprazole
triple therapy for 1-2wks -> continue PPI for 4-6wks

2nd line: quadraple therapy:
+ bismuth

Question 29

H2 inhibitor clinical use (famotidine)

Answer 29

inhibit nocturnal acid secretion

Question 30

why H2 has less effects for meal induced acid secretion

Answer 30

gastric parietal cell also receives stimulation directly from the vagus nerve and gastrin = blocking H2 receptors cannot fully inhibit gastric acid secretion
esp when not on empty stomach