Effect of a single oral dose of rabeprazole on nocturnal acid breakthrough and nocturnal alkaline amplitude

Effects of obesity on the pharmacology of proton pump inhibitors: current understanding and future implications for patient care and research

INTRODUCTION

In the United States, obesity affects approximately ⅖ adults and ⅕ children, leading to increased risk for comorbidities, like gastroesophageal reflux disease (GERD), treated increasingly with proton pump inhibitors (PPIs). Currently, there are no clinical guidelines to inform PPI dose selection for obesity, with sparse data regarding whether dose augmentation is necessary.

AREAS COVERED

We provide a review of available literature regarding the pharmacokinetics (PK), pharmacodynamics (PD), and/or metabolism of PPIs in children and adults with obesity, as a step toward informing PPI dose selection.

EXPERT OPINION

Published PK data in adults and children are limited to first-generation PPIs and point toward reduced apparent oral drug clearance in obesity, with equipoise regarding obesity impact on drug absorption. Available PD data are sparse, conflicting, and limited to adults. No studies are available to inform the PPI PK→PD relationship in obesity and if/how it differs compared to individuals without obesity. In the absence of data, best practice may be to dose PPIs based on CYP2C19 genotype and lean body weight, so as to avoid systemic overexposure and potential toxicities, while monitoring closely for efficacy.

Modulations in extracellular calcium lead to H+-ATPase-dependent acid secretion: a clarification of PPI failure

The H⁺,K⁺-ATPase was identified as the primary proton secretory pathway in the gastric parietal cell and is the pharmacological target of agents suppressing acid secretion. Recently, we identified a second acid secretory protein expressed in the parietal cell, the vacuolar H⁺-ATPase (V-type ATPase). The aim of the present study was to further characterize H⁺-ATPase activation by modulations in extracellular calcium via the calcium sensing receptor (CaSR). Isolated gastric glands were loaded with the pH indicator dye BCECF-AM [2',7'-bis-(2-carboxyethyl)-5-(and-6)-carboxyfluorescein acetoxymethyl ester] to measure intracellular pH. Experiments were conducted in the absence of sodium and potassium to monitor H⁺-ATPase-specific transport activity. CaSR was activated with the calcimimetic R568 (400 nM) and/or by modulations in extracellular Ca²⁺. Elevation in calcium concentrations increased proton extrusion from the gastric parietal cell. Allosteric modification of the CaSR via R568 and calcium increased vacuolar H⁺-ATPase activity significantly (ΔpH/min_lowCa²⁺_(0.1mM) = 0.001 ± 0.001, ΔpH/min_normalCa²⁺_(1.0mM) = 0.033 ± 0.004, ΔpH/min_highCa²⁺_(5.0mM) = 0.051 ± 0.005). Carbachol significantly suppressed calcium-induced gastric acid secretion via the H⁺-ATPase under sodium- and potassium-free conditions. We conclude that the V-type H⁺-ATPase is tightly linked to CaSR activation. We observed that proton pump inhibitor (PPI) exposure does not modulate H⁺-ATPase activity. This elevated blood calcium activation of the H⁺-ATPase could provide an explanation for recurrent reflux symptoms while taking a PPI therapy. NEW & NOTEWORTHY This study emphasizes the role of the H⁺-ATPase in acid secretion. We further demonstrate the modification of this proton excretion pathway by extracellular calcium and the activation of the calcium sensing receptor CaSR. The novelty of this paper is based on the modulation of the H⁺-ATPase via both extracellular Ca (activation) and the classical secretagogues histamine and carbachol (inactivation). Both activation and inactivation of this proton pump are independent of PPI modulation.

Proton pump inhibitors drastically modify triosephosphate isomerase from Giardia lamblia at functional and structural levels, providing molecular leads in the design of new antigiardiasic drugs

BACKGROUND

Proton pump inhibitors (PPIs) are extensively used in clinical practice because of their effectiveness and safety. Omeprazole is one of the best-selling drugs worldwide and, with other PPIs, has been proposed to be potential drugs for the treatment of several diseases. We demonstrated that omeprazole shows cytotoxic effects in Giardia and concomitantly inactivates giardial triosephosphate isomerase (GlTIM). Therefore, we evaluated the efficiency of commercially available PPIs to inactivate this enzyme.

METHODS

We assayed the effect of PPIs on the GlTIM WT, single Cys mutants, and the human counterpart, following enzyme activity, thermal stability, exposure of hydrophobic regions, and susceptibility to limited proteolysis.

RESULTS

PPIs efficiently inactivated GlTIM; however, rabeprazole was the best inactivating drug and was nearly ten times more effective. The mechanism of inactivation by PPIs was through the modification of the Cys 222 residue. Moreover, there are important changes at the structural level, the thermal stability of inactivated-GlTIM was drastically diminished and the structural rigidity was lost, as observed by the exposure of hydrophobic regions and their susceptibility to limited proteolysis.

CONCLUSIONS

Our results demonstrate that rabeprazole is the most potent PPI for GlTIM inactivation and that all PPIs tested have substantial abilities to alter GITIM at the structural level, causing serious damage.

GENERAL SIGNIFICANCE

This is the first report demonstrating the effectiveness of commercial PPIs on a glycolytic parasitic enzyme, with structural features well known. This study is a step forward in the use and understanding the implicated mechanisms of new antigiardiasic drugs safe in humans.

Controlling on-demand gastric acidity in obese subjects: a randomized, controlled trial comparing a single dose of 20 mg rabeprazole and 20 mg omeprazole

Background

Obesity is associated with a risk of gastroesophageal reflux disease. The pharmacodynamic efficacy of proton pump inhibitors has not been specifically evaluated in obese subjects. The aim of this study was to compare the antisecretory response to a single oral dose of 20 mg rabeprazole, 20 mg omeprazole and placebo in obese subjects.

Methods

Gastric pH was monitored for 24 hours on three separate occasions in eighteen H. pylori-negative, asymptomatic obese subjects. Subjects were given omeprazole, rabeprazole or placebo in a randomized order and in a double-blind fashion. The main analysis criterion was 24-h percent of time post dose with intragastric pH above 3; secondary criteria were percentage of time above pH 4, median pH, [H+] concentrations and nocturnal acid breakthrough (NAB). Results were analyzed using linear mixed models and Wilks test comparing variances.

Results

24-h median [IQ] percentages of time with gastric pH above 3 and 4 were higher with rabeprazole than omeprazole (46 [37–55] vs. 30 [15–55] %, 9 [5-11] % for placebo) but the differences did not reach statistical significance (p = 0.11 and 0.24, respectively). Median acid concentrations were significantly lower with rabeprazole than with omeprazole and placebo (22 [14–53] vs. 54 [19–130] and 95 [73–170] mmoles/l, p < 0.01) for all periods. The number of NAB was significantly lower with rabeprazole than with omeprazole (median 1 [1,2] vs. 2 [1-3], p = 0.04). Variances of 24-h data (pH above 3 and 4, median pH, [H+] concentrations) were significantly lower with rabeprazole than with omeprazole (p < 0.0001).

Conclusions

In asymptomatic obese subjects the gastric antisecretory response to a single dose of rabeprazole and omeprazole was strong and not significantly different between drugs despite a significantly more homogeneous response with rabeprazole.

Trial registration

ClinicalTrial.gov: NCT01136317

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.

Comparative efficacy of rabeprazole and pantoprazole in the control of nocturnal Acid output and intragastric acidity

BACKGROUND/AIMS

Nocturnal reflux is a largely undiagnosed and unmanaged condition predisposing to multiple esophageal complications. We evaluated the effects of rabeprazole and pantoprazole on nocturnal intragastric pH and gastric acid output during Day 1 of therapy following the consumption of standard meals.

METHODS

The study had a double-blinded, randomized, two-way crossover design, and involved 15 patients with a history of mild reflux. Following an overnight fast, patients were given either rabeprazole (20 mg) or pantoprazole (40 mg) prior to the first of three standard Western meals. They then underwent overnight continuous intragastric pH monitoring and gastric acid output measurement. The drug effect was analyzed using a two-treatment, two-period crossover mixed model.

RESULTS

The percentage of time during which the mean intragastric pH was greater than 4.0 and gastric acid output was less than 2.0 was higher for oral rabeprazole (p<0.05). The inhibition of acid output was greater for rabeprazole at almost all time points. Furthermore, the mean time-matched pH values differed significantly over the first 8.3 hours (p<0.05).

CONCLUSIONS

On day 1, oral rabeprazole inhibited acid output to a greater extent and for a longer period than pantoprazole, and the intragastric pH was significantly higher for rabeprazole than for pantoprazole over the first 8.3 hours.

A review of rabeprazole in the treatment of acid-related diseases

Rabeprazole is a proton pump inhibitor. Pharmacodynamic data show rabeprazole can achieve optimal acid suppression since the first administration and can maintain this advantage in the following days of therapy. Moreover, rabeprazole has the highest pKa (~ 5.0, the pH at which a drug becomes 50% protonated), and hence the molecule can be activated at higher pH levels much faster than other PPIs. Due to its peculiar catabolic pathway, ie, a prevalent metabolism through a non-enzymatic pathway, rabeprazole is less susceptible to the influence of genetic polymorphisms for CYP2C19, resulting in minor influences on its pharmacokinetics and pharmacodynamics. In terms of clinical efficacy, rabeprazole 20 mg uid or 10 mg bid produced healing rates at 8 weeks similar to those obtained with omeprazole 20 mg uid in erosive esophagitis patients, and in NERD patients doses of 10 or 20 mg are equivalent and both are better than placebo at 2 and 4 weeks. To prevent symptomatic relapse, on-demand strategy with rabeprazole 10 mg daily appears to be ideal, due to its rapidity of onset; results on NERD patients have documented its superiority over placebo. Continuous treatment, however, up to 5 years, seems to achieve better results than on-demand therapy, particularly in patients with esophagitis. It is debated whether in the latter halved doses (10 mg) are really equivalent to full dose (20 mg). Rabeprazole has been used with success in the treatment of some atypical GERD manifestations, such as dysphagia associated with GERD, GERD-related asthma and chest-pain, and in the therapy of Barrett's esophagus. Finally, rabeprazole achieves similar Helicobacter pylori eradication rates compared with omeprazole and lansoprazole when co-administrated with low or high doses of antibiotics (amoxicillin and clarithromycin). In addition, low doses of rabeprazole (10 mg/bid) may be effective in eradicating the pathogen.

Pharmacodynamic effects of single doses of rabeprazole 20 mg and pantoprazole 40 mg in patients with GERD and nocturnal heartburn

BACKGROUND

Rabeprazole and pantoprazole are both used for symptomatic treatment of gastro-oesophageal reflux disease (GERD). Speed and duration of acid suppression and intensity of effect after a single dose may be important pharmacodynamic properties in clinical use.

AIM

To compare antisecretory effects of single doses of rabeprazole and pantoprazole in patients with GERD and a history of nocturnal heartburn.

METHODS

An open-label, randomized, two-way crossover, clinical pharmacology study was conducted. Twenty-nine Helicobacter pylori-negative GERD patients (17 men, mean age 44 years), with a history of nocturnal heartburn (mean frequency 4.7 episodes/week), received a single dose of rabeprazole 20 mg or pantoprazole 40 mg, with a 14-day 'washout'. Intragastric pH was recorded continuously from 24 h before to 24 h after dosing.

RESULTS

Mean area under the intragastric pH-time curve (AUC) was significantly higher after dosing with rabeprazole 20 mg than with pantoprazole 40 mg in all time intervals analysed, including night (P </= 0.02). Mean percentage time with pH > 3 and >4 was significantly greater after rabeprazole than pantoprazole in all time intervals (P </= 0.004).

CONCLUSION

In GERD patients with nocturnal heartburn, a single oral dose of rabeprazole 20 mg increased intragastric pH more than pantoprazole 40 mg did throughout the 24 h after dosing.

Review article: efficacy and safety of rabeprazole in treating gastroesophageal reflux disease

Proton pump inhibitors (PPI) are the mainstay of gastroesophageal reflux disease (GERD) treatment. They have a good efficacy and short- and long-term safety profile. Rabeprazole is a second generation PPI with rapid onset of action that quickly relieves symptoms of GERD. Rabeprazole consistently and profoundly inhibits gastric acid secretion. Its metabolism is less dependent on CYP4502C19 system and therefore is the least affected among all PPIs by CYP4502C19 genetic polymorphism. Recent studies have also indicated that rabeprazole on-demand is cost effective in preventing non-erosive reflux disease (NERD) symptom relapse.