Drugs affecting Acid Secretion

Question 1

What are the 3 main drug classes used in the treatment of peptic disorder?
Give relevant examples

Answer 1

• Antacids - e.g. aluminium hydroxide, Gaviscon
• H2 receptor antagonists - e.g. Ranitidine, Cimetidine
• PPIs - e.g. Omeprazole, Lansoprazole

Question 2

What is composition of the antacids and hence their mechanism of action?

Answer 2

Usually contain an antacid and an alginate
Antacid component buffers stomach acid
Alginate increases viscosity of stomach contents, which reduces reflux

Question 3

Are there any important ADRs associated with antacids?

Answer 3

No

Question 4

Are there any important DDIs associated with antacids?

Answer 4

Yes
May bind to and reduce absorption of other drugs - reduce their efficacy
E.g. ACEi, PPIs, thyroxine

Question 5

How are antacids administered?

Answer 5

Chewable tablet or oral suspension

Question 6

Give an example of an H2 receptor antagonist

Answer 6

Ranitidine

Question 7

What is the mechanism of action of the H2 receptor antagonists?

Answer 7

Reduce gastric secretion by blocking H2 receptors on gastric parietal cells - reduces histamine-driven acid production

Question 8

List 2 common ADRs of H2 receptor antagonists

Answer 8

Bowel disturbance

Headache

Question 9

How often must H2 receptor antagonists be taken?

Answer 9

Twice a day - short half-life

Question 10

Give 3 examples of proton pump inhibitors

Answer 10

Lansoprazole
Omeprazole
Esomeprazole

Question 11

What is the mechanism of action of PPIs?

Answer 11

Block the proton pump (H+-ATPase) in gastric parietal cells, hence suppressing gastric acid production almost entirely.

Question 12

Give 2 common ADRs of PPIs
Give 1 serious ADR
Give 1 long-term consequence

Answer 12

• GI disturbance
• Headache
• Hypomagnesaemia
• Increased risk of osteoporosis

Question 13

Give an important ADR of Omeprazole

Answer 13

Interferes with anti-platelet action of Clopidogrel - reduces its activation by CYP450