GI: H2-antagonists

Question 1

How do H2-receptor antagonists bring relief in gastric and duodenal ulcers?

Answer 1

They reduce gastric acid output as a result of H2-receptor blockade:

They do not inhibit the producton at the terminal phase like PPIs though.

Question 2

How do the H2-antagonists differ in terms of duration of action?

Answer 2

Fomotidine and ranitidine are longer-acting than cimetidine with fewer adverse effects and fewer drug interactions.

Question 3

What is the most common side effect of famotidine?

Answer 3

Headache

Question 4

What is the most common side effet of cimetidine?

Answer 4

Diarrhoea, dizziness, headache, rashes and gynecomastia can occur.

Also rarely impotence and loss of libido.

Question 5

What is the most common side effect of ranitidine?

Answer 5

Headache

Question 6

The overall risk of what infection is about 1 in 4 higher among H2-antagonist users?

Answer 6

Pneumonia:

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3042441/

Question 7

How can PPIs or H2 antagonists lead to hypocobalaminaemia?

Answer 7

Causes of hypocobalaminaemia include inadequate dietary intake, pernicious anaemia, intrinsic factor deficiency, achlorhydria (deficiency of gastric acid) - which can be caused by PPI or H2 antagonists as gastric acid is needed to assist B12 absorption.

Question 8

For all H2 antagonists: what reactions occur particularly in the elderly or very ill?

Answer 8

Psychiatric reactions including confusion, depression and hallucinations