Upper GI pharmacology Flashcards
What are antacids?
What are some prototypical examples?
Buffering agents (weak bases that neutralize acid)
CaCO3 (“Tums”), Mg(OH)2, Al(OH)3
What are some side effects of buffering agents?
osmotic diarrhea (from Mg) or constipation (from Ca, Al)
How/where do buffering agents work?
Act locally in stomach and bind H+ to increase pH
What would buffering agents be used to treat?
Heartburn and dyspepsia
What is a prototypical H2 Antagonist?
Ranitidine
“-tidine”
How do H2 antagonists work? (MOA)
H2 antagonists (reversibly) block the histamine H2 receptor interaction.
This reduces stimulation of the proton pump (H+/K+ ATPase)
This prevents the release of acid (basal and meal-stimulated) –> especially nocturnal acid secretion.
This causes the pH to increase.
What are the pharmacokinetics of H2 antagonists?
Given orally, rapidly absorbed
Eliminated by kidneys.
What are H2 antagonists used to treat?
GERD, PUD, dyspepsia, prevention of bleeding from stress-related gastritis
What is the side effect profile of H2 antagonists?
Usually well-tolerated.
May have diarrhea, constipation, headache, drowsiness, fatigue, muscle pain.
Compare H2 antagonists to PPIs with respect to efficacy.
PPIs are more efficacious than H2 antagonists,
but PPIs are also more expensive than H2 antagonists
What is the main goal of an H2 antagonist?
Reducing acid secretion
can reduce daily acid secretion by about 60-70%
What is a prototypical PPI?
Omeprazole
“-prazole”
What do PPIs do?
Suppresses acid by inhibiting the proton pump (which normally secretes acid into stomach lumen).
What determines the amount of gastric acid in the stomach?
Secretion of H+ from parietal cells via the proton pump (H+/K+ ATPase)
What is the MOA of PPIs?
- enter parietal cell
- bind to proton pump (IRREVERSIBLE INACTIVATION)
- -> decreases [H+] in stomach
- effects last until new pumps are made (effects can last up to 48 hrs after single dose).
