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Omeprazole: Difference between revisions

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m sulfinyl not sulfonyl sulfur
 
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| legal_CA_comment = <ref>{{cite web | title=Product monograph brand safety updates | website=[[Health Canada]] | date=7 July 2016 | url=https://www.canada.ca/en/health-canada/services/drugs-health-products/drug-products/drug-product-database/label-safety-assessment-update/product-monograph-brand-safety-updates.html | access-date=1 April 2024}}</ref>
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Long-term use of PPIs is strongly associated with the development of benign [[polyp (medicine)|polyps]] from [[fundic glands]] (which is distinct from [[fundic gland polyposis]]); these polyps do not cause cancer and resolve when PPIs are discontinued. No association is seen between PPI use and cancer, but use of PPIs may mask gastric cancers or other serious gastric problems and physicians should be aware of this effect.<ref name="Corleto2014">{{cite journal | vauthors = Corleto VD, Festa S, Di Giulio E, Annibale B | title = Proton pump inhibitor therapy and potential long-term harm | journal = Current Opinion in Endocrinology, Diabetes, and Obesity | volume = 21 | issue = 1 | pages = 3–8 | date = February 2014 | pmid = 24310148 | doi = 10.1097/med.0000000000000031 | s2cid = 205791135 | hdl = 11573/618643 }}</ref>
 
There is a possible association between long term use and [[dementia]] which requires further study to confirm.<ref>{{cite journal | vauthors = Eusebi LH, Rabitti S, Artesiani ML, Gelli D, Montagnani M, Zagari RM, Bazzoli F | title = Proton pump inhibitors: Risks of long-term use | journal = Journal of Gastroenterology and Hepatology | volume = 32 | issue = 7 | pages = 1295–1302 | date = July 2017 | pmid = 28092694 | doi = 10.1111/jgh.13737 | doi-access = free }}</ref>
 
A review article in ''[[U.S. Pharmacist]]'' in 2013 states that long-term use of PPIs is associated with [[Hypocalcaemia|decreased calcium absorption]] (causing increased risk of [[osteoporosis]] and [[Bone fracture|fractures]]), [[Magnesium deficiency|decreased magnesium absorption]] (causing [[Electrolyte imbalance|electrolyte disturbances]]), and increased risk of certain infections such as ''[[C. difficile]]'' and [[community-acquired pneumonia]]. They hypothesize that this is due to decreased stomach acid production.<ref>{{cite journal | vauthors = O'Neill LW, Culpepper BL, Galdo JA |title=Long-Term Consequences of Chronic Proton Pump Inhibitor Use | journal = US Pharmacist | date = 2013 | volume = 38 | issue = 12 | pages = 38–42 |url= https://www.uspharmacist.com/article/longterm-consequences-of-chronic-proton-pump-inhibitor-use|access-date=28 December 2020 |archive-date=21 January 2021|archive-url=https://web.archive.org/web/20210121163435/https://www.uspharmacist.com/article/longterm-consequences-of-chronic-proton-pump-inhibitor-use|url-status=live}}</ref>
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This interaction is possible because omeprazole is an [[enzyme inhibitor|inhibitor]] of the enzymes [[CYP2C19]] and [[CYP3A4]].<ref>{{cite journal | vauthors = Shirasaka Y, Sager JE, Lutz JD, Davis C, Isoherranen N | title = Inhibition of CYP2C19 and CYP3A4 by omeprazole metabolites and their contribution to drug-drug interactions | journal = Drug Metabolism and Disposition | volume = 41 | issue = 7 | pages = 1414–1424 | date = July 2013 | pmid = 23620487 | pmc = 3684819 | doi = 10.1124/dmd.113.051722 }}</ref> [[Clopidogrel]] is an inactive [[prodrug]] that partially depends on CYP2C19 for conversion to its active form. Inhibition of CYP2C19 may block the activation of clopidogrel, which could reduce its effects.<ref>{{cite journal | vauthors = Lau WC, Gurbel PA | title = The drug-drug interaction between proton pump inhibitors and clopidogrel | journal = CMAJ | volume = 180 | issue = 7 | pages = 699–700 | date = March 2009 | pmid = 19332744 | pmc = 2659824 | doi = 10.1503/cmaj.090251 }}</ref><ref>{{cite journal | vauthors = Norgard NB, Mathews KD, Wall GC | title = Drug-drug interaction between clopidogrel and the proton pump inhibitors | journal = The Annals of Pharmacotherapy | volume = 43 | issue = 7 | pages = 1266–1274 | date = July 2009 | pmid = 19470853 | doi = 10.1345/aph.1M051 | s2cid = 13227312 }}</ref>
 
Almost all [[benzodiazepines]] are metabolised by the CYP3A4 and [[CYP2D6]] pathways, and inhibition of these enzymes results in a higher [[Area under the curve (pharmacokinetics)|area under the curve]] (''i.e.'', the total effect over time of a given dose). Other examples of drugs dependent on CYP3A4 for their metabolism are [[escitalopram]],<ref>{{EMedicine|article|1879354|Selective Serotonin Reuptake Inhibitors and CYP2D6}}</ref> [[warfarin]],<ref name="pmid12724615">{{cite journal | vauthors = Daly AK, King BP | title = Pharmacogenetics of oral anticoagulants | journal = Pharmacogenetics | volume = 13 | issue = 5 | pages = 247–252 | date = May 2003 | pmid = 12724615 | doi = 10.1097/00008571-200305000-00002 }}</ref> [[oxycodone]], [[tramadol]], and [[oxymorphone]]. The concentrations of these drugs may increase if they are used concomitantly with omeprazole.<ref name=Stedman>{{cite journal | vauthors = Stedman CA, Barclay ML | title = Review article: comparison of the pharmacokinetics, acid suppression and efficacy of proton pump inhibitors | journal = Alimentary Pharmacology & Therapeutics | volume = 14 | issue = 8 | pages = 963–978 | date = August 2000 | pmid = 10930890 | doi = 10.1046/j.1365-2036.2000.00788.x | s2cid = 45337685 }}</ref>
 
Omeprazole is also a competitive inhibitor of [[p-glycoprotein]], as are other PPIs.<ref>{{cite journal | vauthors = Pauli-Magnus C, Rekersbrink S, Klotz U, Fromm MF | title = Interaction of omeprazole, lansoprazole and pantoprazole with P-glycoprotein | journal = Naunyn-Schmiedeberg's Archives of Pharmacology | volume = 364 | issue = 6 | pages = 551–557 | date = December 2001 | pmid = 11770010 | doi = 10.1007/s00210-001-0489-7 | s2cid = 19990184 }}</ref>
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==Pharmacology==
Omeprazole irreversibly blocks the enzyme system on parietal cells that is needed for the secretion of gastric acid. It is a specific H{{sup|+}}/K{{sup|+}}ATPase inhibitor. This is the enzyme needed for the final step in the secretion of gastric acid.<ref name=":0">{{cite journal | vauthors = Howden CW | title = Clinical pharmacology of omeprazole | journal = Clinical Pharmacokinetics | volume = 20 | issue = 1 | pages = 38–49 | date = January 1991 | pmid = 2029801 | doi = 10.2165/00003088-199120010-00003 | s2cid = 25855436 }}</ref>
 
===Mechanism of action===
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The absorption of omeprazole takes place in the small intestine and is usually completed within 3 to 6 hours. The systemic [[bioavailability]] of omeprazole after repeated doses is about 60%.<ref>{{cite journal | vauthors = Cederberg C, Andersson T, Skånberg I | title = Omeprazole: pharmacokinetics and metabolism in man | journal = Scandinavian Journal of Gastroenterology. Supplement | volume = 166 | issue = sup166 | pages = 33–40 | date = 1 January 1989 | pmid = 2690330 | doi = 10.3109/00365528909091241 }}</ref> Omeprazole has a volume of distribution of 0.4 L/kg. It has high plasma protein binding of 95%.<ref name="Omeprazole"/>
 
Omeprazole, as well as other PPIs, are only effective on active H<sup>+</sup>/K<sup>+</sup>-ATPase pumps. These pumps are stimulated in the presence of food to aid in digestion. For this reason, patients should be advised to take omeprazole with a glass of water, on anbefore emptya stomachmeal.<ref>{{cite journal | vauthors = Katz PO, Gerson LB, Vela MF | title = Guidelines for the diagnosis and management of gastroesophageal reflux disease | journal = The American Journal of Gastroenterology | volume = 108 | issue = 3 | pages = 308–28; quiz 329 | date = March 2013 | pmid = 23419381 | doi = 10.1038/ajg.2012.444 | s2cid = 8198975 | doi-access = free }}</ref> Additionally, most sources recommend that after taking omeprazole, at least 30 minutes should be allowed to elapse before eating<ref>{{cite web|url=http://medical-dictionary.thefreedictionary.com/omeprazole|title=Omeprazole, in The Free Medical Dictionary|access-date=11 November 2010|archive-date=12 June 2011|archive-url=https://web.archive.org/web/20110612172513/http://medical-dictionary.thefreedictionary.com/omeprazole|url-status=live}}</ref><ref>{{cite web|url=https://www.drugs.com/monograph/omeprazole.html|title=Omeprazole|publisher=Drugs.com|access-date=11 November 2010|url-status=live|archive-url=https://web.archive.org/web/20110219135631/http://www.drugs.com/monograph/omeprazole.html|archive-date=19 February 2011}}</ref> (at least 60 minutes for immediate-release omeprazole plus sodium bicarbonate products, such as Zegerid),.<ref name="Zegerid OTC FDA label" />
 
Omeprazole is completely metabolized by the [[cytochrome P450]] system, mainly in the liver, by [[CYP2C19]] and [[CYP3A4]] [[Isozyme|isoenzymes]].<ref name=Dav2015 /> 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.<ref name=":1" /> Omeprazole has a half life of 0.5 to 1 hour.<ref name=":1">{{cite web |title=Omeprazole |url=https://www.drugbank.ca/drugs/DB00338 |website=www.drugbank.ca |access-date=29 January 2019 |archive-date=30 January 2019 |archive-url=https://web.archive.org/web/20190130053122/https://www.drugbank.ca/drugs/DB00338 |url-status=live }}</ref>
 
==Chemistry==
Omeprazole contains a tricoordinated sulfonylsulfinyl sulfur in a pyramidal structure and therefore can exist as either the (''S'')- or (''R'')-[[enantiomer]]s. Omeprazole is a [[racemate]], an equal mixture of the two. In the acidic conditions of the [[canaliculus (parietal cell)|canaliculi]] of [[parietal cells]], both enantiomers are converted to [[achiral]] products ([[sulfenic acid]] and [[sulfenamide]] configurations) which react with a [[cysteine]] group in [[Hydrogen potassium ATPase|H<sup>+</sup>/K<sup>+</sup> ATPase]], thereby inhibiting the ability of the parietal cells to produce [[gastric acid]].{{citation needed|date=March 2016}}
 
:[[File:Omeprazole Mechanism V1.svg|500px|Omeprazol rearrangement in the body]]