Lecture 33 - Drugs and the gut

Question 1

H2 Receptor antagonist characteristics?

Answer 1

competitive antagonist, rapid action, tolearnce development (tachyphylaxis)

Question 2

H2 antagonist problems?

Answer 2

not effective in heartburn & moderate/severe reflux, multiple dosing, half acid suppression maximum, recurrence of peptic ulcers

Question 3

H2 receptor location?

Answer 3

Gastric parietal cells

Question 4

Proton pump location?

Answer 4

gastric parietal cells

Question 5

Proton Pump inhibitor mechanism of action?

Answer 5

Omeprazole (e.g.) absorbed in blood, reaches parietal cell, passes into canaliculi, converted into sulphonamide by acid, reacts w cysteine

Question 6

Proton pump inhibitor effectiveness?

Answer 6

Irreversible blockage of proton pump allows long duration of effect, isn’t overridden by histamine, gastrin or Ach stimulation, >90% effectiveness

Question 7

Uses of P.P inhibitors?

Answer 7

gastro-oesophageal reflux disease, NSAID cause ulcer diseases, acute ulcer bleeding

Question 8

Problems w prolonged acid secretion inhibition?

Answer 8

Malabsorption (B12, Fe, Ca), bacterial overgrowth, lesser sterilisation of food, ECL atrophy to high gastrin

Question 9

Problem and solutions w pancreatic enzyme ingestion?

Answer 9

Degradation by acid - enteric coated capsules or take w P.P inhibitors

Question 10

Enteric coating?

Answer 10

Capsule dissolves rapidly in stomach releasing hundreds of minimicrospheres which rapidly disintegrate in duodenum to release enzymes

Question 11

Methods to prolong drug activation to large intestine? e.g. 5-ASA?

Answer 11

join two molecules with azo bond (only cleaved by colonic bacteria), enteric coating, pH/time-dependent release

Question 12

COX2 function?

Answer 12

catalyses formation of inflammatory prostaglandins, inhibiting effects cytoprotective prostaglandins, reducing risk of bleeding but increasing risk of myocardial infarction