Acid Suppression Flashcards
(20 cards)
What is the function of gastric acid in digestion?
Gastric acid creates the optimal pH for digestive enzymes like pepsin and gastric lipase and stimulates pancreatic bicarbonate secretion.
Name two common clinical conditions associated with excessive gastric acid secretion.
Peptic ulceration and gastro-oesophageal reflux disease (GORD).
How do NSAIDs contribute to the development of gastric ulcers?
NSAIDs reduce mucus production, leaving the stomach lining vulnerable to acid damage.
What rare syndrome involves a gastrin-producing tumour leading to excess acid secretion?
Zollinger-Ellison syndrome.
How many parietal cells are found in the human stomach approximately?
About 1 billion.
What enzyme is essential in the parietal cell for acid production?
Carbonic anhydrase.
What happens when vesicles containing H+/K+ ATPase fuse with the parietal cell membrane?
They facilitate acid secretion into the stomach lumen.
Which three chemicals stimulate acid secretion by acting on parietal cells?
Acetylcholine, gastrin, and histamine.
What chemical is released from D cells to inhibit acid production?
Somatostatin.
What is the mechanism of action of muscarinic receptor antagonists like pirenzepine?
They block M1 receptors, reducing acetylcholine-mediated stimulation of acid secretion.
Which was the first orally active H2 receptor antagonist?
Metiamide.
What serious side effect led to metiamide being discontinued?
Agranulocytosis - a serious condition characterized by a severe lack of neutrophils, a type of white blood cell, in the blood, making individuals highly susceptible to infections
What is the Kd (dissociation constant) of cimetidine for the H2 receptor?
42 nM.
hy did ranitidine (Zantac) become more popular than cimetidine?
It had fewer side effects, lower CYP450 interaction, and longer duration of action.
Why was ranitidine withdrawn from the market in 2019?
It was found to contain a cancer-causing nitrosamine impurity.
Which H2 antagonist has no CYP450 or androgen receptor interaction but lower sales due to price?
Famotidine (PEPCID).
What is the mechanism of action of proton pump inhibitors (PPIs)?
They irreversibly bind to H+/K+ ATPase pumps in parietal cells after acid-catalyzed activation.
Why are PPIs formulated with acid-resistant coatings?
o prevent destruction by gastric acid and allow absorption in the duodenum.
How long does it typically take PPIs to reach steady-state inhibition of acid secretion?
About 3 days.
Name one CCK2 receptor antagonist that inhibits gastrin effects.
Netazepide.
