<unk>  irreversibly blocks the enzyme system on parietal cells that is needed for the secretion of gastric acid. It is a specific H+/K+ATPase inhibitor. This is the enzyme needed for the final step in the secretion of gastric acid. Mechanism of action<unk>  is a selective and irreversible proton pump inhibitor. It suppresses stomach acid secretion by specific inhibition of the H+/K+-ATPase system found at the secretory surface of gastric parietal cells. Because this enzyme system is regarded as the acid (proton, or H+) pump within the gastric mucosa,<unk>  inhibits the final step of acid production.<unk>  also inhibits both basal and stimulated acid secretion irrespective of the stimulus as it blocks the last step in acid secretion. The drug binds non-competitively so it has a dose-dependent effect. The inhibitory effect of<unk>  occurs within 1 hour after oral administration. The maximum effect occurs within 2 hours. The duration of inhibition is up to 72 hours. When<unk>  is stopped, baseline stomach acid secretory activity returns after 3 to 5 days. The inhibitory effect of<unk>  on acid secretion will plateau after 4 days of repeated daily dosing. Pharmacokinetics The absorption of<unk>  takes place in the small intestine and is usually completed within 3 to 6 hours. The systemic bioavailability of<unk>  after repeated doses is about 60%.<unk>  has a volume of distribution of 0.4 L/kg. It has high plasma protein binding of 95%.<unk> , as well as other PPIs, are only effective on active H+/K+-ATPase pumps. These pumps are stimulated in the presence of food to aid in digestion. For this reason, patients should be advised to take<unk>  with a glass of water on an empty stomach. Additionally, most sources recommend that after taking<unk> , at least 30 minutes should be allowed to elapse before eating (at least 60 minutes for immediate-release<unk>  plus sodium bicarbonate products, such as Zegerid), though some sources say that with delayed-release forms of<unk> , waiting before eating after taking the medication is not necessary.<unk>  is completely metabolized by the cytochrome P450 system, mainly in the liver, by CYP2C19 and CYP3A4 isoenzymes. Identified metabolites are the sulfone, the sulfide, and hydroxy-omeprazole, which exert no significant effect on acid secretion. About 77% of an orally given dose is excreted as metabolites in the urine, and the remainder is found in the feces, primarily originating from bile secretion.<unk>  has a half life of 0.5 to 1 hour. The pharmacological effects of<unk>  last longer as it is covalently bonded to proton pump on parietal cells to induce effects.
Omeprazole
Rabeprazole
Esomeprazole
Lansoprazole
Dexlansoprazole
Tenatoprazole
Pantoprazole
Ranitidine