UNDER REVIEW (September 2016)
Mechanism of Action:
Metoclopramide is a dopamine D2 receptor antagonist in the central nervous system. This action interferes with the central mechanisms that create the sensation of nausea and also stimulates lower oesophageal sphincter contraction and gastric motility. These pharmacological effects make metoclopramide a useful drug in nausea/vomiting and gatric motility disorders.
Lecture and CAL materials:
UNDER REVIEW (September 2016)
Mechanism of Action:
Proton pump inhibitor that blocks H+/K+ ATPase (proton pump) in parietal cells. Omeprazole is a pro-drug and a weak base which is inactive at neutral pH. It is activated in the acidic environment of the canaliculi of parietal cells and is usually enteric-coated to avoid premature activation. The active form binds covalently to sulphydryl groups in the proton pump, irreversibly inhibiting it. Under normal conditions, rises in cAMP and Ca2+ in parietal cells of stomach activate the proton pump which exchanges H+ in the cell with K+ in the lumen of the gastric gland. Proton pump inhibitors inhibit the process and so reduce gastric acid secretion very effectively. Its effects are evident for up 3 days because it stays in the canaliculi. To start acid secretion once again, new proton pumps have to be made, a process that takes about 18 hours. Proton pump inhibitors cause gastrin levels to rise – gastrin is a natural stimulator of acid secretion in the stomach, and levels of gastrin rise when acid levels are low.
Lecture and CAL materials:
UNDER REVIEW (September 2016)
Mechanism of Action:
Ranitidine is a histamine H2-receptor antagonist. Histamine, released from enterochromaffin (mast-like) cells in the stomach, activates histamine H2 receptors (seven-transmembrane G-protein-coupled receptors) which promote acid secretion. Being a reversible competitor of histamine at H2 receptors on parietal cells, ranitidine prevents histamine-induced gastric acid secretion. It also indirectly inhibits gastrin- and acetylcholine-stimulated gastric acid secretion, which also results in reduced secretion of pepsin (digestive enzyme that hydrolyzes protein).
Lecture and CAL materials:
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