Plasma concentration of rabeprazole after 8-week administration in gastroesophageal reflux disease patients and intragastric pH elevation

A review of medical therapy for proton pump inhibitor nonresponsive gastroesophageal reflux disease

Up to 40% of patients report persistent gastroesophageal reflux disease (GERD) symptoms despite proton pump inhibitor (PPI) therapy. This review outlines the evidence for medical therapy for PPI nonresponsive GERD. A literature search for GERD therapies from 2005 to 2015 in PubMed, EMBASE, Cochrane Central Register of Controlled Trials, and the Cochrane Database of Systematic Reviews identified 2928 unique citations. Of those, 40 unique articles specific to the impact of PPI metabolizer genotype on PPI response and the use adjunctive medical therapies were identified. Thirteen articles reported impacts on CYP genotypes on PPI metabolism demonstrating lower endoscopic healing rates in extensive metabolizers; however, outcomes across genotypes were more uniform with more CYP independent PPIs rabeprazole and esomeprazole. Twenty-seven publications on 11 adjunctive medications showed mixed results for adjunctive therapies including nocturnal histamine-2 receptor antagonists, promotility agents, transient lower esophageal sphincter relaxation inhibitors, and mucosal protective agents. Utilizing PPI metabolizer genotype or switching to a CYP2C19 independent PPI is a simple and conservative measure that may be useful in the setting of incomplete acid suppression. The use of adjunctive medications can be considered particularly when the physiologic mechanism for PPI nonresponse is suspected. Future studies using adjunctive medications with improved study design and patient enrollment are needed to better delineate medical management options before proceeding to antireflux interventions.

Rapid metabolizer genotype of CYP2C19 is a risk factor of being refractory to proton pump inhibitor therapy for reflux esophagitis

BACKGROUND

Proton pump inhibitors (PPIs) are mainly metabolized by cytochrome P450 2C19 (CYP2C19) and used as the first-line therapy for gastroesophageal reflux disease (GERD). However, while several studies have examined the influence of CYP2C19 polymorphism on GERD treatment with PPIs, most have had small sample sizes and were conducted in a single center. Here, we used meta-analysis to investigate whether or not the CYP2C19 rapid metabolizer (RM) genotype is a risk factor for GERD patients being refractory to PPI therapy.

METHODS

PubMed and other electronic databases were systematically searched up to August 2014 using the following terms: "GERD and CYP2C19", "esophagitis and CYP2C19", and "non-erosive reflux disease and CYP2C19." Searches were limited to publications in English, and two investigators evaluated eligible studies and extracted data.

RESULTS

The total efficacy rate of PPIs for GERD, including reflux esophagitis (RE) and non-erosive reflux disease, was 56.4% (95% confidence interval [CI]; 53.9-58.9%, 870/1543) in intention-to-treat analysis and 63.8% (95%CI; 61.3-66.2%, 950/1489) in per-protocol analysis. Efficacy rates varied significantly between CYP2C19 genotypes (intention-to-treat analysis: RMs, 52.2% [315/604]; intermediate metabolizers, 56.7% [298/526]; poor metabolizers [PMs], 61.3% [138/225]; P = 0.047). Among RE patients, CYP2C19 RMs had an increased risk of being refractory to PPI therapy compared with PMs (odds ratio: 1.661, 95% CI: 1.023-2.659, P = 0.040).

CONCLUSIONS

The present meta-analysis demonstrates that CYP2C19 RMs with RE have an increased risk of being refractory to PPI therapy compared with PMs. Individualized dosing regimen with PPIs based on CYP2C19 genotype might be a valid therapeutic strategy for overcoming insufficient gastric acid inhibition.

Development of alginate-reinforced chitosan nanoparticles utilizing W/O nanoemulsification/internal crosslinking technique for transdermal delivery of rabeprazole

AIMS

First; to develop rabeprazole (RP)-alginate core coated chitosan nanoparticles (NP) utilizing water in oil (W/O) nanoemulsion technique. Second; formulation of transdermal patches loaded RP-NP that avoid drug peroral acid sensitivity and first pass effect.

MAIN METHODS

The influence of six factors on RP-NP formulation was investigated using Plackett-Burman (PB) design. The studied factors were considered for their effect on particle size (Y1) and loading efficiency (Y2). Formulation optimum desirability was identified; a proposed formulation was prepared and characterized. In vitro permeation of the prepared NP compared with RP was studied. Transdermal patches loaded drug or RP-NP were prepared and characterized. Patches ex vivo permeation through rat skin was studied, and kinetic analysis and permeation mechanism were investigated.

KEY FINDING

Chitosan, oil phase and surfactant to oil ratios had significant effects on Y1, while Y2 was significantly affected by the same variables affecting Y1 and span80-tween80 ratio. Scanning electron microscope imaging illustrated sphericity of the NP. The optimized RP-NP exhibited sustained release pattern. The prepared patches showed a minimal patch to patch variable. Patches loaded RP-NP exhibited substantial skin permeability and controlled drug release, and were in favor of Fickian diffusion.

SIGNIFICANCE

Transdermal patches loaded RP-NP is effective drug delivery and alternative to drug peroral route.

Individualized therapy for gastroesophageal reflux disease: potential impact of pharmacogenetic testing based on CYP2C19

The main therapeutic agent for gastroesophageal reflux disease (GERD) is a proton pump inhibitor (PPI). Plasma levels and the acid inhibitory effect of PPIs depend on the activity of cytochrome P450 (CYP) 2C19, which is polymorphic. Genotypes of CYP2C19 are classified into three groups: rapid metabolizers (RMs: *1/*1), intermediate metabolizers (IMs: *1/*X), and poor metabolizers (PMs: *X/*X), where *1 and X represent the wild type and the mutant allele, respectively. RMs include ultra-rapid metabolizers, who possess the CYP2C19*17 allele. The pharmacokinetics and pharmacodynamics of PPIs differ among different CYP2C19 genotype groups. Plasma PPI levels and intragastric pH values during PPI treatment are lowest in the RM group, intermediate in the IM group, and highest in the PM group. These CYP2C19-genotype-dependent differences in the pharmacokinetics and pharmacodynamics of PPIs influence the healing and recurrence of GERD during PPI treatment, suggesting the need for CYP2C19 genotype-based tailored therapy for GERD. CYP2C19 pharmacogenetics should be taken into consideration for the personalization of PPI-based therapy. However, the clinical usefulness of CYP2C19 genotype testing in GERD therapy should be verified in clinical studies.

Individualized therapy for gastroesophageal reflux disease: potential impact of pharmacogenetic testing based on CYP2C19

The main therapeutic agent for gastroesophageal reflux disease (GERD) is a proton pump inhibitor (PPI). Plasma levels and the acid inhibitory effect of PPIs depend on the activity of cytochrome P450 (CYP) 2C19, which is polymorphic. Genotypes of CYP2C19 are classified into three groups: rapid metabolizers (RMs: *1/*1), intermediate metabolizers (IMs: *1/*X), and poor metabolizers (PMs: *X/*X), where *1 and X represent the wild type and the mutant allele, respectively. RMs include ultra-rapid metabolizers, who possess the CYP2C19*17 allele. The pharmacokinetics and pharmacodynamics of PPIs differ among different CYP2C19 genotype groups. Plasma PPI levels and intragastric pH values during PPI treatment are lowest in the RM group, intermediate in the IM group, and highest in the PM group. These CYP2C19-genotype-dependent differences in the pharmacokinetics and pharmacodynamics of PPIs influence the healing and recurrence of GERD during PPI treatment, suggesting the need for CYP2C19 genotype-based tailored therapy for GERD. CYP2C19 pharmacogenetics should be taken into consideration for the personalization of PPI-based therapy. However, the clinical usefulness of CYP2C19 genotype testing in GERD therapy should be verified in clinical studies.

Update on the pharmacogenomics of proton pump inhibitors

Proton pump inhibitors (PPIs) are widely used for the treatment of gastroesophageal reflux disease as well as other acid-related disorders. PPIs are metabolized primarily via the CYP2C19 and CYP3A4 isoenzymes; their activity is influenced both by exogenous and endogenous (pharmacogenetic) factors. The CYP2C19 polymorphism affects the metabolism of PPIs, causing large individual pharmacokinetic variations. Differences in the CYP2C19-mediated metabolism can produce marked interpatient variability in acid suppression, in drug-interaction potential and in clinical efficacy. Understanding the pharmacokinetic properties of PPIs and examining the pharmacogenetic alterations may help clinicians optimize PPI therapy and administer individual treatment, especially to nonresponder patients with gastroesophageal reflux disease or ulcer or after failed eradication therapy.

Study of the pharmacokinetics and intragastric pH of rabeprazole given as successive intravenous infusion to healthy Chinese volunteers

OBJECTIVES

To investigate the pharmacokinetics and pharmacodynamics of rabeprazole (RPZ) given as successive intravenous infusion to healthy Chinese volunteers.

METHODS

A total of 63 subjects (33 males and 30 females) were recruited at four research centers and given a 5-day therapeutic course of RPZ (10, 20, or 40 mg) administered as single daily doses during a 30-min period. Plasma concentrations were monitored by sampling at very short intervals for the first 330, 360, or 420 min post-RPZ administration. Intragastric pH was recorded 24 h post-RPZ administration on day 1 and day 5.

RESULTS

After receiving a single and repeated doses of RPZ, the area under the plasma concentration-time curve (AUC(0-τ)) was 51.9 ± 22.1, 96.7 ± 27.6, and 188.4 ± 65.8 mg·min/L on day 1 and 59.3 ± 23.9, 106.7 ± 27.8, and 200.3 ± 79.0 mg·min/L on day 5 for the low-, middle-, and high-dose groups, respectively. The corresponding peak concentrations (C(max)) were 0.64 ± 0.11, 1.30 ± 0.26, and 2.6 ± 0.54 μg/mL on day 1 and 0.76 ± 0.15, 1.39 ± 0.25, and 2.91 ± 0.53 μg/mL on day 5, respectively. Although the mean AUC and C(max) values increased from a single dose to repeated doses in the three groups, the difference was not significant. The mean AUC((0, τ)) and C(max) ratios of repeated dose to single dose were 1.14, 1.10, and 1.06 on day 1 and 1.19, 1.07, and 1.12 on day 5 for the low-, middle-, and high-dose groups, respectively. After administration of a single dose, the 24-h pH value was significantly higher in the high-dose group than in the low-dose group. After repeated doses, significant increases in pH were observed in the low-, middle-, and high-dose groups; however, the between-group differences were not statistically significant.

CONCLUSIONS

There is a relationship between the pharmacokinetics and pharmacodynamics of RPZ, with the latter depending in part on the duration of administration, as evidenced by a higher AUC or C(max) and intragastric pH from repeated dosing.

Efficacy and safety of rabeprazole in non-steroidal anti-inflammatory drug-induced ulcer in Japan

AIM: To investigate the efficacy and safety of rabeprazole under continuous non-steroidal anti-inflammatory drug (NSAID) administration for NSAID-induced ulcer in Japan.

METHODS: Subjects comprised patients undergoing NSAID treatment in whom upper gastrointestinal endoscopy revealed an ulcerous lesion (open ulcer) with diameter ≥ 3 mm, who required continuous NSAID treatment. Endoscopies were performed at the start of treatment, during the treatment period, and at the conclusion (or discontinuation) of treatment. Findings were evaluated as size (maximum diameter) and stage based on the Sakita-Miwa classification. An ulcer was regarded as cured when the “white coating” was seen to have disappeared under endoscopy. As criteria for evaluating safety, all medically untoward symptoms and signs (adverse events, laboratory abnormalities, accidental symptoms, etc.) occurring after the start of rabeprazole treatment were handled as adverse events.

RESULTS: Endoscopic cure rate in 38 patients in the efficacy analysis (endoscopic evaluation) was 71.1% (27/38). Among those 38 patients, 35 had gastric ulcer with a cure rate of 71.4% (25/35), and 3 had duodenal ulcer with a cure rate of 66.7% (2/3). Three adverse drug reactions were reported from 64 patients in the safety analysis (interstitial pneumonia, low white blood cell count and pruritus); thus, the incidence rate for adverse drug reactions was 4.7% (3/64).

CONCLUSION: The treatment efficacy of rabeprazole for NSAID-induced ulcer under continuous NSAID administration was confirmed.

Polymorphism of human cytochrome P450 enzymes and its clinical impact

Pharmacogenetics is the study of how interindividual variations in the DNA sequence of specific genes affect drug response. This article highlights current pharmacogenetic knowledge on important human drug-metabolizing cytochrome P450s (CYPs) to understand the large interindividual variability in drug clearance and responses in clinical practice. The human CYP superfamily contains 57 functional genes and 58 pseudogenes, with members of the 1, 2, and 3 families playing an important role in the metabolism of therapeutic drugs, other xenobiotics, and some endogenous compounds. Polymorphisms in the CYP family may have had the most impact on the fate of therapeutic drugs. CYP2D6, 2C19, and 2C9 polymorphisms account for the most frequent variations in phase I metabolism of drugs, since almost 80% of drugs in use today are metabolized by these enzymes. Approximately 5-14% of Caucasians, 0-5% Africans, and 0-1% of Asians lack CYP2D6 activity, and these individuals are known as poor metabolizers. CYP2C9 is another clinically significant enzyme that demonstrates multiple genetic variants with a potentially functional impact on the efficacy and adverse effects of drugs that are mainly eliminated by this enzyme. Studies into the CYP2C9 polymorphism have highlighted the importance of the CYP2C9*2 and *3 alleles. Extensive polymorphism also occurs in other CYP genes, such as CYP1A1, 2A6, 2A13, 2C8, 3A4, and 3A5. Since several of these CYPs (e.g., CYP1A1 and 1A2) play a role in the bioactivation of many procarcinogens, polymorphisms of these enzymes may contribute to the variable susceptibility to carcinogenesis. The distribution of the common variant alleles of CYP genes varies among different ethnic populations. Pharmacogenetics has the potential to achieve optimal quality use of medicines, and to improve the efficacy and safety of both prospective and currently available drugs. Further studies are warranted to explore the gene-dose, gene-concentration, and gene-response relationships for these important drug-metabolizing CYPs.

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.