Upper GI Pharmacology

Question 1

Why are obesity and pregnancy risk factors for GORD?

Answer 1

. Obesity increases intra-abdominal pressure, so easier for stomach contents to be pushed up into oesophagus
. Pregnancy causes increased intra-abdominal pressure, and also hormones cause upper oesophageal sphincter to relax

Question 2

What is a common drug treatment for pregnant women with GORD?

Answer 2

Antacids because they are very safe for pregnancy

Question 3

What is the most common cause of duodenal ulcers? How does it cause ulcers?

Answer 3

. H.pylori bacterial infection

. Chronic gastritis can lead to ulceration

Question 4

Give 3 tests for H.pylori

Answer 4

. Urea breath test
. Biopsy- test for urease activity
. Antigen testing/ antibodies present in stool, saliva, blood

Question 5

Why is the production of urease important for the survival of H. pylori’s?

Answer 5

. Urease converts urea to ammonia and carbon dioxide

. Ammonia neutralises stomach acid to allow H. pylori to survive

Question 6

What is melaena? What is it a sign of?

Answer 6

Melaena are black tarry stools, often occurring with gastric bleeds when blood is partially digested and comes out black

Question 7

Name three substances which act to increase acid secretion

Answer 7

Histamine (binds to H2-receptors in stomach), gastrin, acetylcholine (binds to M3 receptors) –> switch on proton pump

Question 8

Name two substances which act to decrease acid secretion

Answer 8

Prostaglandins (switches off proton pump), bicarbonate

Question 9

What do antacids do?

Answer 9

Neutralise stomach acid to relieve GORD symptoms (doesn’t treat underlying problem though)

Question 10

How do alginates work?

Answer 10

Alginic acid combines with saliva to form a viscous foam, which sits on top of gastric contents as a protective raft –> protects oesophagus during reflux

Question 11

How do histamine H2 antagonists work?

Answer 11

Block H2-receptors, which blocks signal to proton pump so less H+ pumped out in stomach acid

Question 12

Why are H2 antagonists used to treat peptic ulcers/GORD but antimuscarinics aren’t?

Answer 12

Blocking H2 receptors (histamine action) or M3 receptors (prostaglandin action) both block the signal to PPIs, but blocking M3 receptors would have systemic effects because they’re not specific to the PPI pathway

Question 13

What is the difference between H1 and H2 receptors?

Answer 13

Histamine H1 receptors involved in allergies, histamine H2 receptors involved in gastric PPI stuff

Question 14

PPIs are irreversible, well tolerated, and very effective. What is the main adverse effect of PPIs?

Answer 14

. Inhibit proton pumps so stomach acid less acidic, so weaker defence against invading bacteria
. Higher risk of food poisoning due to achlorhydria (lack of HCl)

Question 15

Outline the triple therapy approach to peptic ulceration

Answer 15

. 2 antibiotics from: amoxicillin, clarithromycin, metronidazole (to prevent infection while having less acidic stomach acid)
. Plus PPI/H2-antagonist (to deal with ulcer)

. Triple therapy for a week, then just PPI alone

Question 16

Why do NSAIDs increase the risk of gastric ulcers?

Answer 16

. Inhibit CoX
. CoX has two isoforms (CoX1 = gastric protection, CoX2=inflammation via prostaglandin)
. NSAIDs aim to reduce inflammation but can then reduce gastric protection at the same time, giving rise to ulcers