Antihistamines Flashcards
What are H2 blockers?
H2 blockers are histamine receptor antagonists that inhibit the parietal cell H2 receptor activation of the proton pump.
antihistamines = H2 antagonists
Name two examples of H2 blockers.
- cimetidine (Tagamet)
- ranitidine (Zantac)
What conditions are treated with H2 blockers?
- Indigestion
- Peptic ulcer disease
- Gastritis
- GERD
- Aspiration pneumonitis
What are the side effects of cimetidine?
- Antiandrogenic effects
- CNS disturbances (if renal or hepatic impairment present)
- Increased risk of bacterial pneumonia
antiandrogenic effects d/t it also binding to androgen receptor;
How does cimetidine affect bacterial pneumonia risk?
Cimetidine increases gastric pH, which can allow bacteria to colonize, leading to secondary colonization in the respiratory tract.
What are the side effects of ranitidine?
Ranitidine has a more favorable side effect profile with rare CNS effects and less interaction with concurrent antacids.
+ STILL a risk of bacterial pneumonia
crosses BBB poorly
Fill in the blank: Histamine is one of the biggest activators of the _______.
[proton pump]
What triggers the release of histamine in gastric endocrine cells?
Gastric endocrine cells are extrachromaffin-like cells that are located near parietal cells
Activation of receptors for gastrin and ACh located near parietal cells.
Describe the activating pathway of histamine in the stomach.
Histamine binds to H2 receptors on parietal cells, leading to proton pump secreting H+ ions into the stomach lumen.
Proton pump (located on surface of parietal cell)
True or False: Ranitidine crosses the blood-brain barrier easily.
False
What can decrease the absorption of H2 blockers?
Concurrent use with antacids due to a change in pH.
