Acid Secretion

Question 1

What are the 2 main classes of drugs currently used to suppress acid secretion
Give examples

Answer 1

H2 receptor antagonists
E.g. Cimetidine

Proton pump inhibitors
E.g. Omeprazole, lanzoprazole

Question 2

H2 receptor antagonists:
Mechanism of action
ADRs

Answer 2

Block H2 receptors on parietal cells, reducing amount of acid produced

Oral admin, well absorbed and side effects rare:
Diarrhoea, dizziness, musc pain, rash, gynaecomastic

Question 3

PPIs:
Mechanism of action
ADRs

Answer 3

Irreversible inhibit proton pump in parietal cells
Only target active pumps bound to membrane (take just before eating)

Headache, diarrhoea, rash, increased gastrin

Question 4

How does stomach acid secretion occur

Answer 4

Parietal cells:
Contain proton pump (H/K/ATPase) on apical membrane
Pump H+ into canaliculus (produced with HCO3- from CO2 and H2O via carbonic anhydrase)
Stimulated by gastrin, histamine, ACh
HCO3- transported out of basolateral membrane in exchange for Cl-, slightly elevating blood pH (alkaline tide)