Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0017168 (gastroesophageal reflux disease)
 11,783 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Gastro-oesophageal reflux disease is probably the most common acid-peptic disease in Western countries, and the successful treatment of mild to moderate disease with pharmacotherapy has become commonplace. A large number of effective drugs are now available, and so the decision-making process for physicians increasingly relies on considerations other than pure efficacy. Cost, adverse effects and drug interactions have therefore become important, particularly in the most vulnerable patients - children, the elderly and patients who are ill and are taking medications that may influence the efficacy of antireflux therapy. Important drug interactions with antacids include the prevention of the absorption of antibacterials such as tetracycline, azithromycin and quinolones. H2 antagonists, proton pump inhibitors and prokinetic agents undergo metabolism by the cytochrome P450 (CYP) system present in the liver and gastrointestinal tract. Cimetidine is an inhibitor of CYP3A and it may cause significant interactions with drugs of narrow therapeutic range and low bioavailability that are metabolised by these enzymes. The gastroparietal proton pump inhibitors lansoprazole, omeprazole and pantoprazole are all primarily metabolised by a genetically polymorphic enzyme, CYP2C19, that is absent from approximately 3% of Caucasians and 20% of Asians. These drugs may also interact with CYP3A, but to a lesser extent. Interactions with prokinetic agents carry the greatest potential for harm. Metoclopramide is a dopamine antagonist that may cause extrapyramidal effects when administered alone at high concentrations, or when coadministered with antipsychotic agents such as haloperidol or phenothiazines. Cisapride is clearly able to prolong the electrocardiographic QT interval and cause lethal ventricular arrhythmias when its metabolism is slowed by interaction with inhibitors of CYP3A, such as erythromycin, ketoconazole or itraconazole.
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PMID:Selection of drugs to treat gastro-oesophageal reflux disease: the role of drug interactions. 1106 15

This article reviews the pharmacokinetics of esomeprazole, the (S)-isomer of the proton pump inhibitor (PPI) omeprazole. Esomeprazole is the first single isomer PPI developed for the treatment of patients with acid-related diseases. In vitro experiments in human liver microsomes demonstrated that the formation of the hydroxy and 5-O-desmethyl metabolites of esomeprazole is via cytochrome P450 (CYP) 2C19, whereas that of the sulphone metabolite is via CYP3A4. The formation rate of the hydroxy metabolite from esomeprazole is lower than for (R)-omeprazole, but that of the 2 other metabolites is higher, demonstrating stereoselective metabolism. The sum of the intrinsic clearances of all 3 metabo- lites for esomeprazole was one-third of that for (R)-omeprazole, suggesting lower clearance of esomeprazole in vivo. In vivo investigations demonstrated that esomeprazole is chirally stable after administration. Esomeprazole is 97% bound to plasma proteins. In normal (extensive) metabolisers with regard to CYP2C19, esomeprazole is metabolised more slowly than omeprazole, resulting in a higher area under the concentration-time curve (AUC) after administration of the same dose. This is more pronounced after repeated administration rather than after a single dose. In poor metabolisers, the AUC is lower for esomeprazole than for omeprazole, contributing to less overall interindividual variability for esomeprazole than for omeprazole. In general, esomeprazole and omeprazole are subject to the same metabolic transformations. Almost complete recoveries were reported and the ratio between urinary and faecal excretion is about 4:1 for both compounds. The dose-dependent increase in AUC of esomeprazole with repeated administration results from a combination of decreased first-pass elimination and decreased systemic clearance. Patients with gastro-oesophageal reflux disease exhibit a pharmacokinetic pattern similar to that in healthy individuals, whereas elderly individuals exhibited a slightly lower metabolism rate. Patients with a severe deficit in their liver function had a lower rate of metabolism, as would be expected, whereas those with mild to moderate liver disease did not exhibit any alteration in the pharmacokinetics. The pharmacokinetics of esomeprazole in individuals with impaired renal function is unlikely to differ from that in healthy individuals. A slight sex difference in the pharmacokinetics of esomeprazole was demonstrated in that the AUC and peak plasma drug concentration were slightly, but not statistically significantly, higher in females than in males.
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PMID:Pharmacokinetic studies with esomeprazole, the (S)-isomer of omeprazole. 1147 67

Cytochrome P450 (CYP) 2C19 mediates the major metabolic transformations of the proton pump inhibitors (PPIs) omeprazole, pantoprazole, lansoprazole, esomeprazole, and rabeprazole. Genetic polymorphism of CYP2C19 can lead to significant phenotypic variation in the activity of this isoenzyme and thus in the metabolism of PPIs. We systematically reviewed the pharmacogenetic studies of PPIs with respect to the effects of CYP2C19 polymorphism on the clinical outcomes of PPI therapy. We searched MEDLINE (January 1966-August 2002) and EMBASE (January 1988-August 2002) for English-language articles on the pharmacogenetics of PPIs; the search was supplemented by a bibliographic review of all relevant articles. Seventeen pertinent citations were identified, and the quality (level) of evidence for each was categorized according to the rating scale of the United States Preventive Services Task Force. We found that the relationship between CYP2C19 genetic polymorphism and clinical outcomes after PPI therapy has not yet been clearly delineated. Virtually all pharmacogenetic studies of PPIs have been performed in Japanese men; thus, the clinical relevance of CYP2C19 genetic polymorphism in non-Asian patients and women is unknown. Differences among dual- and triple-therapy drug regimens make it difficult to compare H. pylori eradication studies and assess their applicability to current practice patterns. Drug adherence, a pivotal factor in the success of eradication therapy, was addressed in only four trials. Future directions for research include performing more studies with larger sample sizes, particularly in non-Asian populations and women; measuring plasma PPI concentrations to directly correlate H. pylori infection and ulcer cure rates with plasma drug availability; expanding the study population to patients with gastroesophageal reflux disease; and exploring the influence of CYP3A4 in the success or failure of PPI therapy. Although CYP2C19 genotyping is currently only a research instrument, it may be a valuable clinical tool in select patients to ensure optimal PPI therapy.
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PMID:Pharmacogenetics of the proton pump inhibitors: a systematic review. 1268 Apr 76

Proton pump inhibitors (PPIs) [omeprazole, lansoprazole, pantoprazole, rabeprazole and esomeprazole] are widely utilised for the treatment of gastro-oesophageal reflux disease, as well as other acid-related disorders. All PPIs suppress gastric acid secretion by blocking the gastric acid pump, H(+)/K(+)-adenosine triphosphatase (ATPase), but the physicochemical properties of these drugs result in variations in the degree of acid suppression, as well as the speed of onset of acid inhibition. Such differences may impact on the clinical performance of PPIs, and this manuscript discusses data that may help clinicians choose between the available PPIs for specific clinical situations and indications. The characteristics of PPIs that have been developed subsequent to omeprazole offer several advantages over this prototype PPI, particularly with respect to the onset of acid suppression and reduced potential for inter-individual pharmacokinetic variation and drug interactions. Newer agents inhibit H(+)/K(+)-ATPase more rapidly than omeprazole and emerging clinical data support potential clinical benefits resulting from this pharmacological property. Although key pharmacokinetic parameters (time to maximum plasma concentration and elimination half-life) do not differ significantly among PPIs, differences in the hepatic metabolism of these drugs can produce inter-patient variability in acid suppression, in the potential for pharmacokinetic drug interactions and, quite possibly, in clinical efficacy. All PPIs undergo significant hepatic metabolism. Because there is no direct toxicity from PPIs, there is minimal risk from the administration of any of them - even to patients with significant renal or hepatic impairment. However, there are significant genetic polymorphisms for one of the cytochrome P450 (CYP) isoenzymes involved in PPI metabolism (CYP2C19), and this polymorphism has been shown to substantially increase plasma levels of omeprazole, lansoprazole and pantoprazole, but not those of rabeprazole. Hepatic metabolism is also a key determinant of the potential for a given drug to be involved in clinically significant pharmacokinetic drug interactions. Omeprazole has the highest risk for such interactions among PPIs, and rabeprazole and pantoprazole appear to have the lowest risk.Thus, whereas all PPIs have been shown to be generally effective and safely used for the treatment of acid-mediated disorders, there are chemical, pharmacodynamic and pharmacokinetic differences among these drugs that may make certain ones more, or less, suitable for treating different patient subgroups. Of course, the absolute magnitude of risk from any PPI in terms of drug-drug interactions is probably low - excepting interactions occurring as class effects related to acid suppression (e.g. increased digoxin absorption or inability to absorb ketoconazole).
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PMID:Clinical pharmacology of proton pump inhibitors: what the practising physician needs to know. 1466 53

Proton pump inhibitors such as omeprazole (esomeprazole), lansoprazole, pantoprazole and rabeprazole are eliminated by the hepatic route and the polymorphic CYP2C19 is mainly involved in their metabolism. In different populations three phenotypes have been identified: extensive metabolizers, poor metabolizers and individuals carrying one wild type and one mutant allele (het extensive metabolizers). Systemic exposure to the proton pump inhibitors as expressed by the AUC (area under the plasma level time profiles) is 5-12-times higher in poor metabolizers than in extensive metabolizers. As the pharmacodynamic response (elevation of intragastric pH) to the proton pump inhibitors is related directly to their AUC, a much higher pH can be monitored over 24 hr in poor metabolizers than in extensive metabolizers. Furthermore, clinical efficacy of all proton pump inhibitors depend on maintaining intragastric pH above certain threshold levels and significantly higher eradication rates of Helicobacter pylori have been observed in patients of the poor metabolizers and het extensive metabolizers phenotype if compared to extensive metabolizers. Likewise, limited data suggest that proton pump inhibitors-induced healing rates in gastro-oesophageal reflux disease are apparently higher in poor metabolizers/het extensive metabolizers than in extensive metabolizers of CYP2C19. Therefore initial genotyping for this enzyme and higher dosage in extensive metabolizers is likely to improve the clinical efficacy of proton pump inhibitors.
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PMID:CYP2C19 polymorphism and proton pump inhibitors. 1524 68

It should be considered that the causes of refractory gastroesophageal reflux disease (GERD) are multifactorial. Esophageal manometry study is useful when we make distinguish patients with esophageal motility disorders from those with refractory GERD. Endoscopic ultrasonography is also performed to observe the thickness of esophageal wall which represents the disturbance of esophageal motor function. Esophageal pH monitoring is useful to detect the acid clearance disturbance and phenomenon of nocturnal acid breakthrough. Both are occurred at night, and are recently considered to be responsible for refractory GERD. Catheter-free pH monitoring system, Bravo, makes it possible to measure esophageal pH under quite physiological conditions. Genotype of CYP2C19 is sometimes checked in patients with PPI resistance GERD. Intra-gastric pH with omeprazole and lansoprazole depends on patient's genotype of CYP2C19. Monitoring of 24-hour bilirubin, Bilitec, is also useful to detect duodeno-gastro-esophageal reflux.
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PMID:[Test of refractory gastroesophageal reflux disease]. 1534 37

Prevalence of refractory gastroesophageal reflux disease (GERD) defined as a patient who have persistent GERD symptoms during treatment with proton pump inhibitor (PPI) is rare in Japanese patinets. Pathogenesis of refractory GERD is associated with several factors including dysfunction of esophageal motility, presence of severe hiatal hernia, complication such as stricture and short esophagus, extensive metabolizer of CYP2C19 genotype, nocturnal gastric acid breakthrough, absence of H. pylori infection, or bile reflux. Examination by 24 hr pH monitoring is necessary to assess refractory GERD and if acid suppression is insufficient, treatment with double doses of PPIs or combination of PPI and H2 blocker is effective. However, most cases of refractory GERD are required surgical treatment. Endoscopic therapy might be useful for refractory GERD in future.
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PMID:[Pathogenesis and treatment of refractory gastroesophageal reflux disease in Japanese patients]. 1534 42

Proton pump inhibitor (PPI) is the first-line drug for GERD and is far more effective than H2-receptor antagonist (H2RA). H2RA suppresses mainly nocturnal gastric acid secretion from parietal cells, while PPI blocks acid production at nighttime as well as daytime when acid refluxes often occur. PPI-test is a therapeutic diagnosis and can reliably distinguish GERD from other diseases presenting similar symptoms. Initial therapy of GERD should be started with a full dose of PPI. However, most of the GERD patients need maintenance therapy. The maintenance dose of PPI should be individualized with a titration technique ('New Step-down therapy'). A small number of GERD patients resistant to PPI therapy may be due to nocturnal acid breakthrough (NAB) or rapid metabolism of PPI (extensive metabolizer for CYP2C19).
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PMID:[PPI: new strategies for GERD]. 1534 53

Proton pump inhibitors are now considered the mainstay of treatment for acid-related disease. Although all proton pump inhibitors are highly effective, the antisecretory effects of different drugs in this class are not completely consistent across patients. One reason for this is the acid-suppressing effect of Helicobacter pylori infection, which may augment the actions of proton pump inhibitors. A second important reason for interpatient variability of the effects of proton pump inhibitors on acid secretion involves genetically determined differences in the metabolism of these drugs. This article focuses on the impact of genetic polymorphism of cytochrome P450 (CYP)2C19 on the pharmacokinetics and pharmacodynamics of proton pump inhibitors, particularly rabeprazole. Results reviewed indicate that the metabolism and pharmacokinetics of rabeprazole differ significantly from those of other proton pump inhibitors. Most importantly, the clearance of rabeprazole is largely nonenzymatic and less dependent on CYP2C19 than other drugs in its class. This results in greater consistency of pharmacokinetics for rabeprazole across a wide range of patients with acid-related disease, particularly those with different CYP2C19 genotypes. The pharmacodynamic profile for rabeprazole is also characterized by more rapid suppression of gastric acid secretion than with other proton pump inhibitors, which is also independent of CYP2C19 genotype. The favourable pharmacokinetic/pharmacodynamic profile for rabeprazole has been shown to result in high eradication rates for H. pylori in both normal and poor metabolizers. Pharmacodynamic results have also suggested that rabeprazole may be better suited than omeprazole as on-demand therapy for symptomatic gastro-oesophageal reflux disease. Finally, the use of rabeprazole is not complicated by clinically significant drug-drug interactions of the type that have been reported for omeprazole.
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PMID:Review article: relationship between the metabolism and efficacy of proton pump inhibitors--focus on rabeprazole. 1549 14

Management of gastro-oesophageal reflux disease (GERD) is aimed at reducing oesophageal acid exposure to achieve symptom relief. Therapy has traditionally included advice to the patient on diet and lifestyle management. Recent evidence suggests, however, that some specific dietary modifications may be applicable to the Japanese patient. For example, ingestion of Japanese sweet cakes or rice cakes should be avoided by the Japanese patient with GERD as these foods may provoke heartburn. Pharmacological therapy is, however, usually also required for effective symptom relief. While antacids and histamine H(2)-receptor antagonists have a role in treating mild GERD, effective relief of many cases of oesophagitis is usually only achieved by using proton-pump inhibitors such as lansoprazole, omeprazole and rabeprazole. In the Japanese population, variation in the genetic polymorphism of CYP2C19 (a cytochrome P450 isoenzyme) leads to considerable inter-individual unpredictability in the activity of lansoprazole and omeprazole due to inter-individual differences in the extent to which these agents are metabolized. Consequently, rabeprazole, which does not undergo hepatic biotransformation by CYP2C19, offers significant advantages over the other PPIs as a result of its more predictable activity. This, coupled with its more rapid onset of action, leads to a more efficient and less variable acid-suppressing effect.
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PMID:Review article: treatment for gastro-oesophageal reflux disease--lifestyle advice and medication. 1557 67


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