Proton pump inhibitors: do differences in pharmacokinetics translate into differences in clinical outcomes?

CYP2C19 genotypes in the pharmacokinetics/pharmacodynamics of proton pump inhibitor-based therapy of Helicobacter pylori infection

IMPORTANCE OF THE FIELD

Proton pump inhibitors (PPIs) are potent gastric acid inhibitors. Therapies with a PPI and antibiotics are used to cure Helicobacter pylori (H. pylori) infection, which is closely related to many gastrointestinal diseases. Most PPIs are mainly metabolized by cytochrome 2C19 (CYP2C19). The genetic polymorphisms of CYP2C19 may lead to the differences in pharmacokinetics (PK), pharmacodynamics (PD) and clinical efficacy of PPIs.

AREAS COVERED IN THIS REVIEW

The roles of PPIs on the eradication of H. pylori are summarized. The impact f CYP2C19 polymorphism on the PK and PD of PPIs is addressed and related to the present status of therapy for H. pylori infection. The opinions on the strategy of PPIs-based therapies of H. pylori infection are provided.

WHAT THE READER WILL GAIN

Update the factors that may influence the PPIs-based therapies of H. pylori infection.

TAKE HOME MESSAGE

The eradication rates of H. pylori infection are significantly different between patients who are CYP2C19 extensive metabolizers and poor metabolizers, partly because of the differences in the PK and PD of PPIs. Nonetheless, the differences can be improved by adjusting the regimens of PPIs and using antibiotics that have less H. pylori-resistance.

A comparative study of proton-pump inhibitor tests for Chinese reflux patients in relation to the CYP2C19 genotypes

BACKGROUND

The proton-pump inhibitor (PPI) test has been proposed as a valuable tool for diagnosing gastroesophageal reflux disease in Western populations.

GOALS

We aim to compare the diagnostic accuracy of the PPI test using rabeprazole and pantoprazole in a Chinese population with a higher prevalence of poor PPI metabolization.

STUDY

After diagnostic endoscopy, patients with gastroesophageal reflux disease symptoms were randomly assigned to a 2-week test with rabeprazole (20 mg b.i.d.) or pantoprazole (40 mg b.i.d.). Therapeutic response was assessed with a 5-grade daily record. Genotypes of cytochrome P450 (CYP) 2C19 polymorphism were determined.

RESULTS

Of the 178 patients who completed the study, 92 (51.7%) had erosive esophagitis and 78 (48.3%) were endoscopy-negative reflux disease. On the basis of 50% reduction of symptoms, there was a nonsignificant difference of diagnostic performances between rabeprazole and pantoprazole. For the CYP2C19 genotypes, 138 (87.3%) were determined to be extensive metabolizers (EMs) and 20 (12.7%) were poor metabolizers (PMs). When comparing the EMs and PMs, the diagnostic specificity in the prediction of erosive esophagitis was higher in the EMs (57.6% vs. 20.0%, P=0.040), as was the accuracy (74.6% vs. 50.0%, P=0.023). There were no differences in the sensitivity, positive predictive value, or negative predictive value.

CONCLUSIONS

CYP2C19 genotypic polymorphism was related to a higher possibility of false-positive results for patients who metabolized PPI poorly. High-dose rabeprazole and pantoprazole showed a similar diagnostic performance.

Rabeprazole: a review of its use in the management of gastric acid-related diseases in adults

Rabeprazole (Aciphex, Alfence, Pariet) is a proton pump inhibitor (PPI) used for the treatment of adults with conditions requiring a reduction of gastric acid secretion such as erosive or ulcerative gastro-oesophageal reflux disease (GORD), non-erosive reflux disease (NERD), duodenal and gastric ulcers, and pathological hypersecretory conditions including Zollinger-Ellison syndrome (ZES). It is also used as part of combination therapy for the eradication of Helicobacter pylori, a pathogen frequently implicated in the development of gastric and duodenal ulcers. Rabeprazole has a well established efficacy and safety profile in the treatment of gastric acid-related diseases. Rabeprazole is a useful, well tolerated and cost-effective option for the treatment of GORD, NERD, peptic ulcer and other gastric acid-related diseases (including ZES), and provides an appropriate alternative to other currently available PPIs, with the added benefits of having a consistent efficacy profile and low drug interaction potential due to its predominantly nonenzymatic metabolism.

Drug-drug interaction between clopidogrel and the proton pump inhibitors

OBJECTIVE

To evaluate the interaction between clopidogrel and proton pump inhibitors (PPIs).

DATA SOURCES

Literature retrieval was accessed through PubMed (1980-January 2009), abstracts from 2008 American Heart Association and 2009 Society of Cardiovascular Angiography and Interventions Scientific Sessions, and media press releases using the terms clopidogrel, proton pump inhibitors, cytochrome 2C19, genetic cytochrome P450 polymorphisms, and drug interaction. In addition, reference citations from publications identified in the search were reviewed.

STUDY SELECTION AND DATA EXTRACTION

Relevant original research articles and review articles were evaluated. Articles were selected if they were published in English and focused on any of the key words or appeared to have substantial content addressing the drug interaction.

DATA SYNTHESIS

Recent attention has been placed on a potential interaction observed between clopidogrel and the widely used PPIs. Preliminary evidence suggests that omeprazole interacts with clopidogrel, reducing clopidogrel's antiplatelet effects as measured by various laboratory tests. Most data indicate that the interaction involves the competitive inhibition of the CYP2C19 isoenzyme. The interaction appears to be clinically significant, as several retrospective analyses have shown an increase in adverse cardiovascular outcomes when PPIs and clopidogrel are used concomitantly. However, this may not be a class effect.

CONCLUSIONS

Available data suggest that omeprazole is the PPI most likely to have a significant interaction with clopidogrel. Further studies are needed to determine that an interaction between the other PPIs and clopidogrel does not exist. In situations in which both clopidogrel and a PPI are indicated, pantoprazole should be used since it is the PPI least likely to interact with clopidogrel.

Gastric secretion

PURPOSE OF REVIEW

This review summarizes the past year's literature regarding the regulation and assessment of gastric acid secretion.

RECENT FINDINGS

Gastric acid secretion is regulated by biologic agents produced and released by enteroendocrine cells and neurons as well as by exogenously administered substances and infection. Too much acid can lead to gastroesophageal reflux disease, peptic ulcer disease, and stress-related erosion/ulcer disease. Too little acid can interfere with the absorption of certain nutrients, predispose to enteric infection, and interfere with the absorption of some medications. Gastrin, histamine, gastrin-releasing peptide, ghrelin, orexin, and glucocorticoids stimulate whereas leptin, glucagon-like peptide 1, and Helicobacter pylori inhibit acid secretion. Helicobacter pylori inhibits the transcriptional activity of HK-ATPase, the proton pump of the parietal cell.

SUMMARY

A better understanding of the pathways and mechanisms regulating gastric acid secretion should lead to improved management of patients with acid-induced disorders as well as those who secrete too little acid.

Proton pump inhibitors: an update of their clinical use and pharmacokinetics

BACKGROUND

Proton pump inhibitors (PPIs) represent drugs of first choice for treating peptic ulcer, Helicobacter pylori infection, gastrooesophageal reflux disease, nonsteroidal anti-inflammatory drug (NSAID)-induced gastrointestinal lesions (complications), and Zollinger-Ellison syndrome.

RESULTS

The available agents (omeprazole/esomeprazole, lansoprazole, pantoprazole, and rabeprazole) differ somewhat in their pharmacokinetic properties (e.g., time-/dose-dependent bioavailability, metabolic pattern, interaction potential, genetic variability). For all PPIs, there is a clear relationship between drug exposure (area under the plasma concentration/time curve) and the pharmacodynamic response (inhibition of acid secretion). Furthermore, clinical outcome (e.g., healing and eradication rates) depends on maintaining intragastric pH values above certain threshold levels. Thus, any changes in drug disposition will subsequently be translated directly into clinical efficiency so that extensive metabolizers of CYP2C19 will demonstrate a higher rate of therapeutic nonresponse.

CONCLUSIONS

This update of pharmacokinetic, pharmacodynamic, and clinical data will provide the necessary guide by which to select between the various PPIs that differ-based on pharmacodynamic assessments-in their relative potencies (e.g., higher doses are needed for pantoprazole and lansoprazole compared with rabeprazole). Despite their well-documented clinical efficacy and safety, there is still a certain number of patients who are refractory to treatment with PPIs (nonresponder), which will leave sufficient space for future drug development and clinical research.

Rabeprazole: a second-generation proton pump inhibitor in the treatment of acid-related disease

Rabeprazole is a proton pump inhibitor (PPI) presenting a very advantageous pharmacodynamic and pharmacokinetic profile over older PPIs. In particular, this drug has a very fast onset of action, due to a short activation time and a very high pKa, and may therefore be defined as a 'second generation' PPI. The aim of this article is to provide an update on the pharmacology and clinical profile of rabeprazole and its use in acid-related disorders, with a particular focus on its role in gastroesophageal reflux disease; in the treatment and prevention of duodenal and gastric ulcers and Zollinger-Ellison syndrome; in the therapy of the extraesophageal manifestations of gastroesophageal reflux disease (in particular the respiratory and ear, nose and throat ones); and in the eradication of Helicobacter pylori.

Control of gastric acid secretion in health and disease

Recent milestones in the understanding of gastric acid secretion and treatment of acid-peptic disorders include the (1) discovery of histamine H(2)-receptors and development of histamine H(2)-receptor antagonists, (2) identification of H(+)K(+)-ATPase as the parietal cell proton pump and development of proton pump inhibitors, and (3) identification of Helicobacter pylori as the major cause of duodenal ulcer and development of effective eradication regimens. This review emphasizes the importance and relevance of gastric acid secretion and its regulation in health and disease. We review the physiology and pathophysiology of acid secretion as well as evidence regarding its inhibition in the management of acid-related clinical conditions.

Comparison of esomeprazole enteric-coated capsules vs esomeprazole magnesium in the treatment of active duodenal ulcer: A randomized, double-blind, controlled study

AIM: To evaluate the efficacy and tolerability of two different preparations of esomeprazole in healing duodenal ulcers.

METHODS: A total of 60 patients with active duodenal ulcers were enrolled and randomized to receive esomeprazole enteric-coated capsules (40 mg) or esomeprazole magnesium (40 mg), once daily, for 4 consecutive wk, with ulcer healing being monitored by endoscopy. Safety and tolerability were also assessed.

RESULTS: Fifty seven patients completed the whole trial. The ulcer healing rates at the end of wk 2 were 86.7% and 85.2% in the esomeprazole enteric-coated capsules and esomeprazole magnesium groups, respectively (P = 0.8410), and reached 100% at the end of wk 4 in both groups. Symptom relief at the end of wk 2 was 90.8% in the esomeprazole enteric-coated capsules group and 86.7% in the esomeprazole magnesium group (P = 0.5406); at the end of wk 4 symptom relief was 95.2% and 93.2%, respectively (P = 0.5786). Adverse events occurred in 16.7% of the esomeprazole enteric-coated capsules group and 14.8% of the esomeprazole magnesium group (P = 1.0000).

CONCLUSION: The efficacies of esomeprazole enteric-coated capsules and esomeprazole magnesium in healing duodenal ulcer lesions and relieving gastrointestinal symptoms are equivalent. The tolerability and safety of both drugs were comparable.