H2 Antagonist ( Ranitidine)

Question 1

What is ranitidine used for?

Answer 1

1) Peptic ulcer disease ( but PPIs are better)

2) GORD / dyspepsia (PPIs are better)

Question 2

How do H2 antagonists work?

Answer 2

• reduce gastric acid secretion.

Physiology:

• Gastric parietal cells secrete H+ into stomach lumen via the proton pump
• Histamine activates acid secretion by binding to H2 receptors of gastric parietal cell wall.
• H2 antagonists block this receptor so proton pump cannot be activated by this pathway.
• BUT there are other pathways to activat acid secretion so H2 antagonists cannot completely suppress secretion (PPIs can!)

Question 3

What are the side effect?

Answer 3

H2 antagonists have few side effects:

• GI disturbance (diarrhoea_
• headache
• dizziness

Question 4

What are the contraindications of H2 antagonists?

Answer 4

1) H2 blockers are excreted by kidneys so reduce dose in renal impairment.

Question 5

What are the drug interactions of ranitidine

Answer 5

No drug interactions

Question 6

In what situation would H2 blockers be the prefered choice over PPIs?

Answer 6

H2 blockers have a more rapid onset than PPIs. So are used for suppressing gastric acid production pre-operatively.

(when lying flat in operations , acid reflux may be aspirated causing penumonitis)