Gastric acid secretion

[arda]

The graph shows gastric acid secretion response versus concentration of histamine administered before (solid curve) and after (dashed curve) the administration of a drug.

What is this drug ? i picked an proton pump inhibitor,

other choices are atropine,cimetidine and diphenhydramine

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[Donald Juan]

I believe the answer is cimetidine. Cimetidine is a competitive histamine H2 antagonist, so the affect of the drug--decreased gastric acid secretion--can be overcome by increasing the concentration of histamine which is what the graph shows. This is a property of all competitive antagonists. A proton pump inhibitor would block the downstream affect of histamine, so even in the face of increased histamine there should still be relatively decreased levels of gastric acid secretion.

 

[arda]

PPI therapy leads to diminished acid secretion, diminished antral D-cell release of somatostatin, consequent increased G-cell release of gastrin and hypergastrinemia. This causes oxyntic cell hyperplasia, increased parietal cell mass, glandular dilatations and stimulation of enterochromaffin-like (ECL) cells to release chromogranin and histamine, raising their concentrations in serum.
I based my thinking on;
Histamine increases with ppi usage,it increases to a point that overcomes the effect of omeprazole

 

[thehundredthone]

Donald Juan's got it absolutely right. PPI's block the H+ pump itself, so neither gastrin nor histamine will have any effect on the acid output.

EDIT:

PPI therapy leads to diminished acid secretion, diminished antral D-cell release of somatostatin, consequent increased G-cell release of gastrin and hypergastrinemia. This causes oxyntic cell hyperplasia, increased parietal cell mass, glandular dilatations and stimulation of enterochromaffin-like (ECL) cells to release chromogranin and histamine, raising their concentrations in serum.
I based my thinking on;
Histamine increases with ppi usage,it increases to a point that overcomes the effect of omeprazole

Why do you believe that the increase in histamine after a point would overcome the PPI?