Rabeprazole: pharmacokinetics in patients with stable, compensated cirrhosis

Proton Pump Inhibitors in Patients with Cirrhosis: Pharmacokinetics, Benefits and Drawbacks

PURPOSE OF REVIEW

This review explores the pharmacokinetics, benefits, and risks of proton pump inhibitors (PPIs) in cirrhotic patients, focusing on the appropriateness of their use and potential adverse effects.

RECENT FINDINGS

Recent studies highlight significant pharmacokinetic alterations in PPIs among cirrhotic patients, with marked increases in lansoprazole and pantoprazole exposure and relatively stable levels of esomeprazole. While effective for managing acid-related disorders and post-band ulcer rebleeding, evidence supporting PPI use for portal hypertension-related bleeding is lacking. Emerging research suggests potential adverse effects such as hepatic decompensation, spontaneous bacterial peritonitis, hepatic encephalopathy, and increased mortality, possibly linked to dysbiosis and bacterial translocation. PPI use in cirrhotic patients alters pharmacokinetics significantly, with esomeprazole potentially safer in advanced cirrhosis. The review advises caution in routine PPI use beyond acid-related conditions due to limited evidence and substantial risks. It underscores the need for careful risk-benefit assessments and exploration of alternative therapies. Future research should aim to identify safer management strategies for portal hypertension complications and to develop evidence-based guidelines for PPI use in patients with cirrhosis.

Sources of Interindividual Variability

The efficacy, safety, and tolerability of drugs are dependent on numerous factors that influence their disposition. A dose that is efficacious and safe for one individual may result in sub-therapeutic or toxic blood concentrations in others. A significant source of this variability in drug response is drug metabolism, where differences in presystemic and systemic biotransformation efficiency result in variable degrees of systemic exposure (e.g., AUC, C_max, and/or C_min) following administration of a fixed dose.Interindividual differences in drug biotransformation have been studied extensively. It is recognized that both intrinsic factors (e.g., genetics, age, sex, and disease states) and extrinsic factors (e.g., diet , chemical exposures from the environment, and the microbiome) play a significant role. For drug-metabolizing enzymes, genetic variation can result in the complete absence or enhanced expression of a functional enzyme. In addition, upregulation and downregulation of gene expression, in response to an altered cellular environment, can achieve the same range of metabolic function (phenotype), but often in a less predictable and time-dependent manner. Understanding the mechanistic basis for variability in drug disposition and response is essential if we are to move beyond the era of empirical, trial-and-error dose selection and into an age of personalized medicine that will improve outcomes in maintaining health and treating disease.

Long-term observation in patients with esophageal varices after endoscopic variceal ligation accompanied with 24-hour pH monitoring

AIM

Esophageal variceal ligation (EVL) is usually carried out to decrease the risk of hemorrhage. Several complications have been reported with the procedure, including bleeding from ligation-induced esophageal ulcers or heartburn. However, there is scant evidence for gastroesophageal reflux caused by EVL. The aim of this study was to assess 24-h pH monitoring in the esophagogastric junction before and after EVL and the bleeding rate for 18 months.

METHODS

We undertook this single-center prospective trial in Kitasato University Hospital (Sagamihara, Japan). We included patients with cirrhosis who were Child-Pugh classification A or B, without uncontrollable hepatocellular carcinoma, and had F2 or larger esophageal varices, and/or were red color sign (RC) positive. The study period was from July 2012 through September 2017 for 32 patients enrolled in this study and followed up until March 2019.

RESULTS

Baseline characteristics were: median Child-Pugh score, 6; and mean age, 64.3 years. Before and after EVL, the median 24-h under pH 4 holding time percentages of all patients were 0.6% (range, 0-5.6%) and 0.95% (range, 0-50.6%), respectively, without a significant difference (P = 0.107). We could not find any G3 or G4 adverse events during this study, and 75% of the patients who had already suffered from moderate gastroesophageal reflux became worse after EVL (P = 0.18) and required antacid therapies. There were no patients with hemorrhage from esophageal varices.

CONCLUSIONS

Esophageal variceal ligation for esophageal varices did not significantly change gastroesophageal reflux. Therefore, acid suppressive therapy might be unnecessary for patients who do not suffer from gastroesophageal reflux after EVL.

Safe use of proton pump inhibitors in patients with cirrhosis

Aims

Proton pump inhibitors (PPIs) belong to the most frequently used drugs, also in patients with cirrhosis. PPIs are extensively metabolized by the liver, but practice guidance on prescribing in cirrhosis is lacking. We aim to develop practical guidance on the safe use of PPIs in patients with cirrhosis.

Methods

A systematic literature search identified studies on the safety (i.e. adverse events) and pharmacokinetics of PPIs in cirrhotic patients. This evidence and data from the product information was reviewed by an expert panel who classified drugs as safe; no additional risks known; additional risks known; unsafe; or unknown. Guidance was aimed at the oral use of PPIs and categorized by the severity of cirrhosis, using the Child–Turcotte–Pugh (CTP) classification.

Results

A total of 69 studies were included. Esomeprazole, omeprazole and rabeprazole were classified as having ‘no additional risks known’. A reduction in maximum dose of omeprazole and rabeprazole is recommended for CTP A and B patients. For patients with CTP C cirrhosis, the only PPI advised is esomeprazole at a maximum dosage of 20 mg per day. Pantoprazole and lansoprazole were classified as unsafe because of 4‐ to 8‐fold increased exposure. The use of PPIs in cirrhotic patients has been associated with the development of infections and hepatic encephalopathy and should be carefully considered.

Conclusions

We suggest using esomeprazole, omeprazole or rabeprazole in patients with CTP A or B cirrhosis and only esomeprazole in patients with CTP C. Pharmacokinetic changes are also important to consider when prescribing PPIs to vulnerable, cirrhotic patients.

Postmarketing surveillance of rabeprazole in upper gastrointestinal peptic lesions in Japanese patients with coexisting hepatic disorders

BACKGROUND

Many Japanese patients with hepatic disorders confirmed on diagnostic imaging and coexisting upper gastrointestinal (GI) peptic lesions receive treatment with proton pump inhibitors. Some pharmacotherapies used to treat peptic ulcers have been associated with adverse drug reactions (ADRs), including elevated liver enzyme levels.

OBJECTIVE

The aim of this study was to determine the tolerability and effectiveness of rabeprazole sodium in treating peptic lesions in patients with coexisting hepatic disorders.

METHODS

This open-label, practice-based, postmarketing surveillance investigation was conducted at 15 centers across Japan. Male and female patients aged ≥18 years with peptic lesions confirmed on upper GI endoscopy and with underlying hepatic disease were enrolled. Patients were randomly assigned to receive rabeprazole 10 or 20 mg PO (tablet) QD after a meal for up to 8 weeks. Tolerability was assessed using monitoring of the incidence of ADRs determined by direct patient questioning, spontaneous reporting, and laboratory assessment. All patients who received at least 1 dose of study drug were included in the tolerability assessment. Effectiveness was assessed at baseline and study end using the rates of achievement of improvement on endoscopy, relief of subjective/objective symptoms (rates of improvement in epigastric pain and heartburn), and global improvement. The effectiveness analysis included all patients with complete data before and after treatment. Subanalyses were conducted to determine the effectiveness of drug by identification of the proportion of patients with coexisting hepatic disorders (cirrhosis, chronic hepatitis, and other hepatic diseases [eg, alcoholic hepatitis, fatty liver]) and by peptic lesion (gastric ulcer, duodenal ulcer, stomal ulcer, and reflux esophagitis) who achieved improvement.

RESULTS

A total of 114 patients were enrolled; 108 patients were included in the tolerability analysis (81 men, 27 women; mean age, 59.9 years; 10-mg dose, 90 patients; 20-mg dose, 18 patients) and 98 patients were included in the analysis of effectiveness. Twenty-one ADRs occurred in 11 (10.2%) patients. Serious ADRs occurred in 2 patients (elevated bilirubin level and hepatic encephalopathy, 1 patient each). Administration of rabeprazole was discontinued in 5 patients due to the occurrence of the following ADRs: constipation (1 patient); epigastric pain (1); dyslalia, disorientation, tremor, sleep disorder, and hepatic encephalopathy (1); diarrhea (1); and elevated alkaline phosphatase and y-glutamyl transpeptidase levels (1). On endoscopy, the proportion of patients achieving improvement with either dose was 30/33 (90.9%). The relief rates assessed using subjective symptoms were 47/55 (85.5%) and 47/56 (83.9%) for epigastric pain and heartburn, respectively. The proportion of patients achieving global improvement with either dose was 80/98 (81.6%) patients (49/62 [79.0%] for cirrhosis, 11/16 [68.8%] for chronic hepatitis, and 20/20 [100.0%] for other hepatic diseases [alcoholic hepatitis, fatty liver]).

CONCLUSION

In this study in Japanese patients with hepatic disorders, rabeprazole was well tolerated and appeared effective for the treatment of upper GI peptic lesions.

Increased rate of spontaneous bacterial peritonitis among cirrhotic patients receiving pharmacologic acid suppression

BACKGROUND & AIMS

Patients with cirrhosis frequently receive proton pump inhibitor (PPI) or H2-receptor antagonist therapies. We investigated whether acid-suppressive therapy is associated with spontaneous bacterial peritonitis (SBP) in cirrhotic patients with ascites.

METHODS

We compared data from 65 hospitalized cirrhotic patients with paracentesis-proven SBP, collected from 2006 to 2009, with those of 65 contemporaneous, hospitalized cirrhotic patients without SBP (controls). We evaluated PPI use and analyzed the effects of covariates.

RESULTS

Patients with SBP had a significantly higher incidence of recent (past 7 days) PPI use (71%) than controls (42%). Of patients with SBP, 68% had no documented indication for PPI therapy. Based on multivariable logistic regression analysis, subjects who had not taken PPIs in the past 90 days were almost 70% less likely to develop SBP than those who had taken PPIs in the previous 7 days. Subjects who took PPIs within 8 to 90 days before hospitalization were 79% less likely to develop SBP than those who took PPIs within 7 days before hospitalization. There was no significant difference between patients who received no PPI therapy in the previous 90 days versus those who had taken PPIs in the previous 8 to 90 days (P = .58). Hyponatremia was associated significantly with SBP. There were no significant differences in length of hospital stay or 30-day survival for the SBP and control groups.

CONCLUSIONS

Pharmacologic acid suppression is associated with SBP in patients with advanced cirrhosis. Prospective studies are needed to determine the mechanism of this association and to determine whether reduced use of PPIs and H2-receptor antagonists reduce the incidence of SBP.

Long-term administration of PPI reduces treatment failures after esophageal variceal band ligation: a randomized, controlled trial

BACKGROUND AND PURPOSE

Elective esophageal variceal ligation (EVL) is performed to decrease the risk of variceal hemorrhage. EVL is associated with adverse effects, including post-ligated bleeding, chest pain, and dysphagia. Proton pump inhibitors (PPIs) are the most potent pharmacological agents for inhibition of gastric acid secretion. However, the long-term effect of PPIs after EVL remains unclear. The aim of this study was to assess the efficacy of rabeprazole, a PPI, after variceal eradication by EVL.

METHODS

We performed a randomized, controlled trial in Kitasato University East Hospital. The primary endpoint was treatment failure, defined as variceal hemorrhage or severe medical complications. Between July 2007 and September 2010, 43 patients were randomized into this study and followed up until September 2010.

RESULTS

Twenty-one patients in the rabeprazole arm received 10 mg rabeprazole daily after EVL, and 22 patients in the control received no antisecretory treatment from the same stage. Baseline characteristics did not differ between the groups (median Child-Pugh score, 6; median age, 62 years; median follow-up, 18.7 months). The trial was stopped early after an interim analysis showed that the risk of bleeding and failure of rabeprazole treatment was lower than that of no antisecretory treatment with the log-rank test showing a significant difference between the groups (P = 0.007) and a hazard ratio of 0.098 [95% confidence interval, 0.012-0.79 (P = 0.029)].

CONCLUSIONS

Long-term administration of PPIs reduced the risk of treatment failure after EVL. Acid suppression therapy should also be considered as a treatment option after EVL.

Pharmacokinetics and tolerability of rabeprazole in children 1 to 11 years old with gastroesophageal reflux disease

BACKGROUND

The pharmacokinetics of rabeprazole after a single oral dose and once-daily administration for 5 consecutive days was characterized in children 1 to 11 years old with gastroesophageal reflux disease (GERD).

PATIENTS AND METHODS

The initial 8 patients received rabeprazole sodium (hereafter referred to as rabeprazole) 0.14 mg/kg (part 1); the next 20 patients were randomized to receive 0.5 or 1 mg/kg (part 2) to target concentrations in plasma expected to be safe and effective. Pharmacokinetic parameters of rabeprazole and the thioether metabolite were calculated using noncompartmental methods. Subjective evaluations of GERD severity, rabeprazole short-term effectiveness, palatability, and safety were also characterized.

RESULTS

Rabeprazole concentrations increased in a dose-dependent manner. Little or no accumulation was observed after repeated administration. The results suggest that formation of the thioether is an important metabolic pathway in young patients, which is consistent with adults. Plasma area under the concentration-time curve values of rabeprazole and the metabolite were poorly correlated with individual age and body weight. Furthermore, oral rabeprazole clearance values (not adjusted for weight) were similar to historical adult data. However, weight-adjusted values were higher for the pediatric patients, and approximately 2 to 3 times the milligram per kilogram dose of rabeprazole in these children was necessary to achieve comparable concentrations in adults. Subjective evaluations demonstrated an improvement of GERD symptoms in most patients after rabeprazole treatment.

CONCLUSIONS

Palatability of the formulation was reported to be good or excellent. Rabeprazole was well tolerated, with no notable differences in safety among the dose groups.

PPIs are not associated with a lower incidence of portal-hypertension-related bleeding in cirrhosis

AIM: To determine if proton pump inhibitor use in cirrhotic patients with endoscopic findings of portal hypertension is associated with a lower frequency of gastrointestinal bleeding.

METHODS: Patients with cirrhosis and endoscopic findings related to portal hypertension, receiving or not receiving proton pump inhibitor (PPI) therapy, were included retrospectively. We assigned patients to two groups: group 1 patients underwent PPI therapy and group 2 patients did not undergo PPI therapy.

RESULTS: One hundred and five patients with a median age of 58 (26-87) years were included, 57 (54.3%) of which were women. Esophageal varices were found in 82 (78%) patients, portal hypertensive gastropathy in 72 (68.6%) patients, and gastric varices in 15 (14.3%) patients. PPI therapy was used in 45.5% of patients (n = 48). Seventeen (16.1%) patients presented with upper gastrointestinal bleeding; in 14/17 (82.3%) patients, bleeding was secondary to esophageal varices, and in 3/17 patients bleeding was attributed to portal hypertensive gastropathy. Bleeding related to portal hypertension according to PPI therapy occurred in 18.7% (n = 9) of group 1 and in 14% (n = 8) of group 2 (odds ratio: 0.83, 95% confidence interval: 0.5-1.3, P = 0.51).

CONCLUSION: Portal hypertension bleeding is not associated with PPI use. These findings do not support the prescription of PPIs in patients with chronic liver disease with no currently accepted indication.

Esomeprazole: potent acid suppression in the treatment of acid-related disorders

Esomeprazole (S-omeprazole), an enantiomer of the racemate omeprazole, is the first proton pump inhibitor to be developed as an isomer. This confers improved pharmacokinetics and pharmacodynamics compared with the racemate R/S-omeprazole. The difference in the pharmacokinetics of esomeprazole compared with omeprazole and the R-isomer is due to reductions in total body clearance and first-pass metabolism in the liver. Pharmacodynamic studies showed that esomeprazole 40 mg provides greater intragastric acid control than respective doses of all the other proton pump inhibitors on the market. Several well-designed clinical trials, employing both endoscopic and symptomatic response criteria, have compared the efficacy of esomeprazole with that of other proton pump inhibitors in the management of gastroesophageal reflux disease patients, and in the eradication of Helicobacter pylori. In addition, the efficacy of esomeprazole for the healing and prevention of nonsteroidal anti-inflammatory drug-associated dyspeptic symptoms and ulcers has been established. The aim of this review is to provide an overview of the pharmacokinetics, pharmacodynamics and consequent clinical importance of esomeprazole in the treatment of acid-related disorders.

Proton pump inhibitors in cirrhosis: Tradition or evidence based practice?

Proton Pump Inhibitors (PPI) are very effective in inhibiting acid secretion and are extensively used in many acid related diseases. They are also often used in patients with cirrhosis sometimes in the absence of a specific acid related disease, with the aim of preventing peptic complications in patients with variceal or hypertensive gastropathic bleeding receiving multidrug treatment. Contradicting reports support their use in cirrhosis and evidence of their efficacy in this condition is poor. Moreover there are convincing papers suggesting that acid secretion is reduced in patients with liver cirrhosis. With regard to Helicobacter pylori (H pylori) infection, its prevalence in patients with cirrhosis is largely variable among different studies, and it seems that H pylori eradication does not prevent gastro-duodenal ulcer formation and bleeding. With regard to the prevention and treatment of oesophageal complications after banding or sclerotherapy of oesophageal varices, there is little evidence for a protective role of PPI. Moreover, due to liver metabolism of PPI, the dose of most available PPIs should be reduced in cirrhotics. In conclusion, the use of this class of drugs seems more habit related than evidence-based eventually leading to an increase in health costs.

Association of galactose single-point test levels and phenytoin metabolic polymorphisms with gingival hyperplasia in patients receiving long-term phenytoin therapy

STUDY OBJECTIVE

To evaluate whether the occurrence or severity of gingival hyperplasia is associated with liver function test results or phenytoin metabolism.

DESIGN

Prospective analysis.

SETTING

University-affiliated medical center in Taipei, Taiwan.

PATIENTS

Sixty-six patients (mean age 37.9 yrs) with epilepsy who were receiving phenytoin for more than 1 year. Intervention. Four blood samples were drawn from each patient for liver function testing, concentrations of phenytoin and its metabolites R-5-(4'-hydroxyphenyl)-5-phenylhydantoin (R-HPPH) and S-HPPH, and genotyping of cytochrome P450 (CYP) 2C9 and 2C19.

MEASUREMENTS AND MAIN RESULTS

Plasma concentrations of phenytoin and its metabolites were determined by a high-performance liquid chromatography method. The CYP2C9 and CYP2C19 genotypes were analyzed by polymerase chain reaction-restriction fragment length polymorphism analysis. Conventional liver function assays and a quantitative liver function test--galactose single-point (GSP) measurement--were performed. Statistical analyses were performed to evaluate the association between liver function test results as well as metabolic phenotype and the occurrence and severity of gingival hyperplasia. Among liver function tests, only GSP levels showed a significant difference between patients with and those without gingival hyperplasia. Patients with an elevated GSP level (> or = 280 microg/ml) had a significantly higher odds ratio (OR 4.51) for the occurrence of gingival hyperplasia. In addition, increased R-HPPH (OR 1.02) and phenytoin (OR 1.09) concentrations were associated with an increased occurrence of gingival hyperplasia. However, only increased GSP and R-HPPH concentrations had significantly higher ORs (2.84 and 1.02, respectively) associated with the severity of gingival hyperplasia. Although mean +/- SD plasma R-HPPH concentration was significantly lower in CYP2C19 poor metabolizers compared with CYP2C9 and CYP2C19 extensive metabolizers and CYP2C9 poor metabolizers (30.38 +/- 16.73 vs 68.22 +/- 44.75 and 78.95 +/- 51.67 microg/ml, respectively), no significant association between genotype and gingival hyperplasia was found.

CONCLUSION

Increased GSP, phenytoin, and R-HPPH concentrations were associated with increased occurrence of phenytoin-induced gingival hyperplasia; only increased GSP and R-HPPH concentrations were associated with increased severity of this adverse effect.

Clinical pharmacological aspects of the proton pump inhibitor therapy – importance of pharmacogenetic differences in the clinical practice

A protonpumpa-gátlók (PPI) a gastrooesophagealis reflux és más savfüggő betegségek kezelésében széles körben használatosak. Az omeprazol, lansoprazol, pantoprazol, rabeprazol és esomeprazol hatékonyan gátolják a gyomorsav-szekréciót a protonpumpa, H + /K + -adenozin trifoszfatáz (ATPáz) bénításával.E vegyületek döntően CYP-mediált oxidatív metabolizmusában megfigyelhető különbségek kifejezett egyéni eltéréseket okozhatnak a savszekréció gátló hatásban. A PPI-kezelés során fellépő gyógyszerkölcsönhatások nagy része szintén e metabolikus folyamatokhoz köthető.A PPI-k átalakításában elsősorban a CYP2C19 és a CYP3A4 izoenzimek vesznek részt; aktivitásukat részben exogén hatások, részben endogén (farmakogenetikai) tényezők módosíthatják. Napjainkban elérhetővé vált az egyes genotípusok (homozigóta extenzív, heterozigóta extenzív metabolizálók és lassú metabolizálók) PCR, DNS chip módszerrel történő vizsgálata, mely egyre több magyarázattal szolgál a terápiás válaszokban megfigyelhető egyéni eltérések megértéséhez.A genotípus meghatározása a klinikai gyakorlat számára jelentős segítséget nyújthat az optimális kezelési forma kiválasztásában, és egyénre szabott savszekréció-gátló terápia kialakításában, különösen PPI-kezelésre non-responder gastrooesophagealis reflux, vagy fekélybetegség esetében, illetőleg sikertelen eradikációs kezelést követően.

Monitoring cytochrome P-450 activity during rabeprazole treatment in patients with gastresophageal reflux disease

Proton pump inhibitors (PPIs) are the cornerstone in the treatment of gastresophageal reflux disease (GORD). PPIs are metabolized by the hepatic cytochrome P-450 enzymes (CYP-450). Rabeprazole is a PPI whose metabolism shows fewer interactions compared to other PPIs. In this study we evaluated the influence of rabeprazole administration on hepatic CYP-450 activity as measured by the (13)C-aminopyrine breath test ((13)C-ABT) in a group of patients with GORD. (13)C-ABT was performed on five GORD patients both before and after 1 week of rabeprazole administration (20 mg, b.i.d.). Pretreatment (13)C-ABT results were compared to posttreatment results. Pre- and posttreatment (13)C-ABT results for patients were compared to those obtained in five controls who did the test twice, with a 1-week interval in between. Before treatment, the (13)C-ABT results for the GORD patients did not significantly differ from those of healthy subjects. After treatment, we observed no significant modification of the (13)C-ABT in GORD patients compared to pretreatment values ((13)C-ABT %dose/hr, 10.56+/-1.31 versus 11.17+/-0.88; (13)C-ABT %cumulative dose, 8.08+/-1.11 versus 8.34+/-0.56). Posttreatment (13)C-ABT results were not significantly different from those obtained in controls at weekly repetition of the test. In patients with GORD, 1-week, full-dose rabeprazole does not display any significant interactions with CYP-450 activity.

Identification of the time-point which gives a plasma rabeprazole concentration that adequately reflects the area under the concentration-time curve

OBJECTIVE

The purpose of this study is to evaluate whether a simple formula using limited blood samples can predict the area under the plasma rabeprazole concentration-time curve (AUC) in co-administration with CYP inhibitors.

METHODS

A randomized double-blind placebo-controlled crossover study design in three phases was conducted at intervals of 2 weeks. Twenty-one healthy Japanese volunteers, including three CYP2C19 genotype groups, took a single oral 20-mg dose of rabeprazole after three 6-day pretreatments, i.e., clarithromycin 800 mg/day, fluvoxamine 50 mg/day, and placebo. Prediction formulas of the AUC were derived from pharmacokinetics data of 21 subjects in three phases using multiple linear regression analysis. Ten blood samples were collected over 24 h to calculate AUC. Plasma concentrations of rabeprazole was measured by an HPLC-assay (l.l.q.=1 ng/ml).

RESULTS

The AUC was based on all the data sets (n=63). The linear regression using two points (C3 and C6) could predict AUC(0-infinity) precisely, irrespective of CYP2C19 genotypes and CYP inhibitors (AUC(0-infinity)=1.39xC3+7.17xC6+344.14, r (2)=0.825, p<0.001).

CONCLUSION

The present study demonstrated that the AUC of rabeprazole can be estimated by the simple formula using two-point concentrations. This formula can be more accurate for the prediction of AUC estimation than that reflected by CYP2C19 genotypes without any determination, even if there are significant differences for the CYP2C19 genotypes. Therefore, this prediction formula might be useful to evaluate whether CYP2C19 genotypes really reflects the curative effect of rabeprazole.

Pharmacokinetics of proton pump inhibitors in children

The use of proton pump inhibitors (PPIs) has become widespread in children and infants for the management of paediatric acid-related disease. Pharmacokinetic profiles of only omeprazole and lansoprazole have been well characterised in children over 2 years of age with acid-related diseases. Few data have been recently published regarding the pharmacokinetics of pantoprazole in children, and none are available for rabeprazole or esomeprazole. The metabolism of PPI enantiomers has never been studied in the paediatric population. A one-compartment model best describes the pharmacokinetic behaviour of omeprazole, lansoprazole and pantoprazole in children, with important interindividual variability for each pharmacokinetic parameter. Like adults, PPIs are rapidly absorbed in children following oral administration; the mean time to reach maximum plasma concentration varies from 1 to 3 hours. Since these agents are acid labile, their oral formulations consist of capsules containing enteric-coated granules. No liquid formulation is available for any of the PPIs. Thus, for those patients unable to swallow capsules, extemporaneous liquid preparations for omeprazole and lansoprazole have been reported; however, neither the absolute nor the relative bioavailabilities of these oral formulations have been studied in children. Intravenous formulations are available for omeprazole (in Europe), lansoprazole and pantoprazole. PPIs are rapidly metabolised in children, with short elimination half-lives of around 1 hour, similar to that reported for adults. All PPIs are extensively metabolised by the liver, primarily by cytochrome P450 (CYP) isoforms CYP2C19 and CYP3A4, to inactive metabolites, with little unchanged drug excreted in the urine. Similar to that seen in adults, the absolute bioavailability of omeprazole increases with repeated dosing in children; this phenomenon is thought to be due to a combination of decreased first-pass elimination and reduced systemic clearance. The apparent clearance (CL/F) of omeprazole, lansoprazole and pantoprazole appears to be faster for children than for adults. A higher metabolic capacity in children as well as differences in the extent of PPI bioavailability are most likely responsible for this finding. This may partly account for the need in children for variable and sometimes considerably greater doses of PPIs, on a per kilogram basis, than for adults to achieve similar plasma concentrations. Furthermore, no studies have been able to demonstrate a statistically significant correlation between age and pharmacokinetic parameters among children. Despite the small number of very young infants studied, there is some evidence for reduced PPI metabolism in newborns. The limited paediatric data regarding the impact of CYP2C19 genetic polymorphism on PPI metabolism are similar to those reported for adults, with poor metabolisers having 6- to 10-fold higher area under the concentration-time curve values compared with extensive metabolisers. Finally, because a pharmacokinetic/pharmacodynamic relationship exists for PPIs, the significant interindividual variability in their disposition may partly explain the wide range of therapeutic doses used in children. Further studies are needed to better define the pharmacokinetics of PPIs in children <2 years of age.

Influence of 1-week Helicobacter pylori eradication therapy with rabeprazole, clarithromycin, and metronidazole on 13C-aminopyrine breath test

Helicobacter pylori eradication therapy is commonly prescribed in the general population. Treatment consists of drugs that are mainly metabolized by the liver cytochrome P-450 (CYP) enzymatic pool. Most H. pylori-infected patients often take drugs for comorbid illnesses, therefore increasing the potential for drug-drug interactions. We aimed to evaluate the interactions of rabeprazole, clarithromycin, and metronidazole 1-week H. pylori eradication therapy with CYP-dependent liver metabolic function in clinical practice. Ten patients referred to our unit for H. pylori infection underwent 1-week eradication therapy with rabeprazole (20 mg, b.i.d.), clarithromycin (500 mg, b.i.d.), and metronidazole (500 mg, b.i.d.). We chose the 13C-aminopyrine breath test (13C-ABT) to evaluate CYP-dependent liver function since it is noninvasive and nonharmful. All patients underwent 13C-ABT at three time points: before therapy (to), at the end of therapy (t8), and after 1 month of follow-up (t38). Mean 13C-ABT dose/hr (t0 = 14.0 +/- 5.4, t8 = 13.5 +/- 4.0, t38 = 16.1 +/- 5.6) as well as 13C-ABT cumulative dose (t0 = 2.4 +/- 1.1, t8 = 2.4 +/- 0.8, t38 = 2.6 +/- 1.0) were not statistically different at the three time points of the study. These results did not seem to be influenced by drugs being administered concomitantly. In everyday clinical practice rabeprazole-based H. pylori eradication therapy does not seem to display any significant interactions with CYP-dependent liver function, even in patients on multiple drugs.

Bioequivalence evaluation of two rabeprazole enteric coated formulations in healthy Chinese volunteers

A bioequivalence study of two rabeprazole enteric-coated formulations was carried out in 20 healthy Chinese volunteers according to a single dose, two-sequence, crossover randomized design. The two formulations were administered in two treatment days, separated by a washout period of 7 days. Blood samples were collected at specified time intervals over 10 hours post-dosing. Plasma samples were separated and assayed for rabeprazole using a selective and sensitive HPLC method with UV detection. The pharmacokinetic parameters AUC(0-T), AUCmax, Cmax, tmax, t(1/2) and MRT were determined from plasma concentration-time profile of both formulations. ANOVA and two one-sided t test procedures showed no significant difference in log-transformed Cmax, AUC(0-T) AUC(0-infinity) while the 90% confidence interval (CI) of the ratio of the geometric means of their values were also used to assess bioequivalence between the two formulations. The results of this study indicated that the two rabeprazole formulations can be considered to be bioequivalent.

The use of proton pump inhibitors in children: a comprehensive review

Proton pump inhibitors (PPIs) belong to a group of chemically related compounds whose primary function is the inhibition of acid production in the final common metabolic pathway of gastric parietal cells. PPIs are highly selective and effective in their action and have few short- or long-term adverse effects. These pharmacologic features have made the development of PPIs the most significant advancement in the management of acid peptic related disorders in the last two decades. There are numerous published adult studies that describe the pharmacology, efficacy and safety of these anti-secretory agents; however, in the pediatric population, there are very few comparable studies, particularly multicenter studies with significant patient enrollment. In preparing this article, our aim was to perform a comprehensive review of the literature on the clinical pharmacology and use of PPIs in the pediatric population, and to briefly review some recent articles. Relevant literature was identified by performing MEDLINE/Pubmed searches from January 1990 to December 2001. Combinations of the following search terms were use to analyze these databases: proton pump inhibitor, children, pediatrics, gastroesophageal reflux disease (GERD), esophagitis, intestinal metaplasia, Helicobacter pylori, omeprazole, lansoprazole, pantoprazole, rabeprazole, esomeprazole, and safety. Abstracts from the 14th annual conference of the North American Society for Pediatric Gastroenterology, Hepatology and Nutrition (NASPGHAN) 2001, and the Disease and Digestive Week 2001, were also included in the review. All pediatric studies reviewed were limited to either omeprazole or lansoprazole. The dosage range used for the management of GERD and related disorders with lansoprazole was 0.73-1.66 mg/kg/day (maximum 30 mg/day). The dosage range for GERD management using omeprazole was 0.3-3.5 mg/kg (maximum 80 mg/day). The dosage range for omeprazole used for H. pylori was 0.5-1.5 mg/kg/day, with a maximum dosage of 40 mg/day, and lansoprazole-containing regimens for H. pylori eradication used dosages ranging from 0.6-1.2 mg/kg/day, with a maximum dosage of 30 mg/day. Few severe adverse events were reported with the use of either drug. Eradication rates for H. pylori were 56-87% for lansoprazole-based triple therapy, and 75-94% for omeprazole-based eradication regimens. To date, there are no published controlled trials of sufficient power comparing the efficacy of the five commercially available PPIs in children, for a variety of acid peptic diseases. Studies suggest that PPIs are highly effective for the management of GERD and related disorders, and are a critically needed component of triple therapy to eradicate H. pylori. PPIs have a very good tolerability profile in adults and children, but long-term tolerability studies are needed, particularly in the pediatric population. Multicenter studies are critically needed to evaluate the second-generation PPIs, to compare PPI efficacy to each other, and to assess the importance of developmental and genetic pharmacology of these drugs in children with acid-peptic disease.

Pharmacokinetic study of esomeprazole in patients with hepatic impairment

OBJECTIVE

To evaluate the pharmacokinetics and safety of esomeprazole (Nexium), the S-isomer of omeprazole, after repeated oral dosing in patients with hepatic impairment.

DESIGN

Single-centre, open-label one-way study.

METHODS

Twelve patients (aged 40-60 years) with mild to severe hepatic impairment received once-daily oral esomeprazole 40 mg for 5 days. Serial blood samples were drawn up to 24 h post-dose on day 5 to determine plasma levels of esomeprazole and its metabolites. Pharmacokinetic parameters were compared with an historical control group of 36 gastro-oesophageal reflux disease (GORD) patients (aged 29-58 years) with normal hepatic function.

RESULTS

Esomeprazole was absorbed rapidly (mean maximum plasma concentration (Cmax) 6.1 micromol/l, mean time to Cmax (tmax) 1.9 h) and eliminated rapidly (mean plasma elimination half-life (t1/2) 2.1 h). Elimination of its pharmacologically inactive sulphone and hydroxy metabolites was more gradual. Patients with mild hepatic impairment had area under the plasma concentration-time curve during the dosage interval (AUCtau) and t1/2 values largely within the range of the control group. In patients with moderate hepatic impairment, t1/2 values were similar and AUCtau was slightly higher than in controls, whereas both parameters were increased in patients with severe hepatic impairment. The mean ratios of esomeprazole AUCtau, Cmax and t1/2 values in patients with and without hepatic impairment were 1.8, 1.3 and 1.3, respectively.

CONCLUSIONS

The steady-state pharmacokinetics of esomeprazole were not altered substantially by mild or moderate hepatic impairment; however, plasma levels of esomeprazole were elevated in severe cases. Thus, dose adjustment appears unwarranted in mild or moderate hepatic impairment, but may be required in some severely impaired patients. Esomeprazole was tolerated well across the spectrum of hepatic impairment.

Rabeprazole: an update of its use in acid-related disorders

Rabeprazole is an inhibitor of the gastric proton pump. It causes dose-dependent inhibition of acid secretion. In 8-week studies, among patients with gastro-oesophageal reflux disease (GORD), rabeprazole 20 mg/day or 10mg twice daily was as effective as omeprazole and superior to ranitidine in the healing of GORD. Symptom relief with rabeprazole was superior to that provided by placebo and ranitidine and similar to omeprazole. In long-term trials rabeprazole 10 mg/day was similar to omeprazole 20 mg/day in a 2-year study and superior to placebo in 1-year studies, in both the maintenance of healing and prevention of symptoms in patients with healed GORD. In nonerosive GORD, 4-week studies have shown rabeprazole to be more effective than placebo in relieving heartburn and various other gastrointestinal symptoms. Data among patients with Barrett's oesophagus suggest rabeprazole 20 mg/day may be more effective than placebo in maintaining healing of associated oesophagitis after 1 year of treatment. One-week triple Helicobacter pylori eradication therapy with rabeprazole plus clarithromycin and amoxicillin achieved eradication rates of > or =85%. Rabeprazole is as effective as omeprazole and lansoprazole when included as part of a triple-therapy regimen for the eradication of H. pylori. Eradication rates of >90% were achieved when rabeprazole 20 to 40 mg/day was included as part of a quadruple eradication regimen. As monotherapy for peptic ulcer healing and symptom relief, 4- to 8-week studies have shown rabeprazole 10 to 40 mg/day to be superior to placebo and ranitidine and have similar efficacy to omeprazole. Preliminary 1-year data among 16 patients with Zollinger-Ellison syndrome suggest rabeprazole 60 to 120 mg/day can resolve and prevent the recurrence of symptoms and endoscopic lesions associated with this condition. In clinical trials of up to 2 years' duration the tolerability of rabeprazole is similar to that of placebo, ranitidine and omeprazole. Common adverse events assigned to rabeprazole have been diarrhoea, headache, rhinitis, nausea, pharyngitis and abdominal pain. Histological changes and increases in serum gastrin levels were unremarkable and typical of proton pump inhibitors. No dosage adjustment is necessary in renal and mild to moderate hepatic impairment.

CONCLUSION

Rabeprazole is a well tolerated proton pump inhibitor. It has proven efficacy in healing, symptom relief and prevention of relapse of peptic ulcers and GORD and can form part of effective H. pylori eradication regimens. It is an important alternative to H(2) antagonists and an additional treatment option to other proton pump inhibitors in the management of acid-related disorders.

Pharmacokinetics of pantoprazole in patients with moderate and severe hepatic dysfunction

BACKGROUND

Patients with impaired hepatic function usually require gastric acid-suppressant therapy but are at increased risk for drug interactions and may require dosage adjustments. The proton pump inhibitor pantoprazole is rapidly absorbed and eliminated, primarily by cytochrome P450 (CYP) 2C19 isozymes.

OBJECTIVE

This study sought to determine whether dosage adjustment of pantoprazole is required in patients with moderate or severe hepatic impairment by comparing the pharmacokinetic profile of pantoprazole in such patients with that in healthy slow metabolizers of pantoprazole, in whom no dosage adjustment is required.

METHODS

Patients with moderate (Child-Pugh class B) and severe (Child-Pugh class C) hepatic impairment received oral pantoprazole 40 mg once daily on days 1 through 4 and then on alternate days (days 6 and 8). Serial blood samples were collected on days 4 and 8 for analyses of plasma pantoprazole concentrations. Pharmacokinetic data were compared between the 2 groups with hepatic impairment and against historical data from 17 healthy subjects who were genetically slow CYP2C19 metabolizers of pantoprazole.

RESULTS

Twenty-two patients participated in the study, 13 in the Child-Pugh class B group and 9 in the Child-Pugh class C group. No clinically significant differences in pantoprazole pharmacokinetics were noted between the patients with hepatic impairment and the healthy slow metabolizers of pantoprazole on days 4 and 8. Pantoprazole was well tolerated. Four Child-Pugh class B patients and 3 Child-Pugh class C patients reported > or = 1 adverse event. Adverse events were generally mild or moderate, and were similar to those reported in healthy subjects. Two patients discontinued the study because of severe events related to their underlying disease.

CONCLUSIONS

The pharmacokinetics and tolerability of pantoprazole were similar in patients with moderate hepatic impairment, patients with severe hepatic impairment, and healthy slow metabolizers of pantoprazole, in whom no dosage adjustment is required. Thus, no dosage adjustment of pantoprazole is required in patients with hepatic impairment, regardless of its severity. However, caution should be exercised when giving pantoprazole to patients with severe hepatic impairment.

Proton pump inhibitors in the treatment of gastro-oesophageal reflux disease

Gastro-oesophageal reflux disease (GERD) is the most common peptic acid disease in the western world and is the commonest indication for acid suppression therapy. Major advances have been made over the past 30 years in the understanding of lower oesophageal sphincter function and the mechanism of acid secretion. Developments in surgical and pharmacological therapy have paralleled these advances. Pharmacotherapy for GERD has evolved from antacids to H2-receptor antagonists (H2RAs) to prokinetics to proton pump inhibitors (PPIs). The H2RAs, while modestly effective in symptom relief and healing of GERD, are limited by pharmacological tolerance. The prokinetics (metoclopramide and cisapride) are limited by low efficacy, pharmacological tolerance and toxicity. The PPIs have emerged as the most effective therapy for symptom relief, healing and long-term maintenance. They have also proved to be remarkably safe and cost-effective in long-term therapy. This review evaluates the pharmacology, efficacy, tolerability, safety and cost-effectiveness of the four currently available PPIs, lansoprazole, omeprazole, pantoprazole and rabeprazole, in the treatment of GERD.

Review article: comparison of the pharmacokinetics, acid suppression and efficacy of proton pump inhibitors

Proton pump inhibitors have dramatically influenced the management of acid-peptic disorders in recent years. They all have a broadly similar mechanism of action and are extensively metabolized in the liver via cytochromes P450 2C19 and 3A4. There is some variation in their potential for drug interactions due to differences in enzyme inhibition. Relatively few serious adverse effects have been reported for the proton pump inhibitors. Comparative studies of acid suppression suggest that lansoprazole and pantoprazole have a potency similar to that of omeprazole on a mg for mg basis; however, rabeprazole may have a greater potency than omeprazole. Lansoprazole and rabeprazole display a more rapid onset of maximal acid suppression than the other proton pump inhibitors. Comparative studies using proton pump inhibitors for the treatment of reflux oesophagitis, duodenal ulcer healing and Helicobacter pylori eradication show little overall difference in outcome between the proton pump inhibitors when used in their standard doses. Lansoprazole and rabeprazole provide earlier and better symptom relief than the other proton pump inhibitors in some studies of peptic ulcer treatment. The few studies of gastric ulcer treatment suggest that there is an advantage in using the proton pump inhibitors that have a higher standard daily dose.

Review article: rabeprazole's tolerability profile in clinical trials

Rabeprazole is a new member of a class of substituted benzimidazole drugs known as proton pump inhibitors. Comparative trials have demonstrated that it is at least as effective as omeprazole for the treatment of gastrooesophageal reflux disease (GERD), duodenal ulcers, or gastric ulcers. It is significantly more effective than histamine2-receptor antagonists for acid suppression, GERD healing and pain relief, and duodenal ulcer healing and pain relief. Adverse events reported during clinical trials provide an important indication of a medication's tolerability. We demonstrate that rabeprazole has a favourable adverse events profile. It is well tolerated in placebo-controlled studies and comparative trials with omeprazole and H2-receptor antagonists. Moreover, no dose adjustments are required for special populations, such as the elderly or patients with renal or mild-to-moderate hepatic disease. Adverse events data from clinical trials support the use of rabeprazole as a treatment for acid-related diseases.

Rabeprazole: a review of its use in acid-related gastrointestinal disorders

Rabeprazole is an inhibitor of the gastric proton pump. It causes dose-dependent inhibition of acid secretion and has a more rapid onset of action than omeprazole. Duodenal ulcers healed faster after treatment with rabeprazole 20 or 40 mg/day than placebo or ranitidine 150 mg 4 times daily and at a generally similar rate to omeprazole 20 mg/day in patients with duodenal ulcers; rabeprazole was similar or superior to these agents in relieving symptoms. Rabeprazole 20 and 40 mg/day healed gastric ulcers faster than placebo, and rabeprazole 20 mg/day healed ulcers at a similar healing rate, to omeprazole 20 mg/day in well controlled 6-week studies. Gastric ulcer symptom relief with rabeprazole was similar or superior to that provided by omeprazole or placebo. In 8-week studies in patients with gastro-oesophageal reflux disease (GERD), rabeprazole 10, 20 and 40 mg/day were more effective than placebo, rabeprazole 20 mg/day was more effective than ranitidine 150 mg twice daily, and rabeprazole 20 mg/day was similar in efficacy to omeprazole 20 mg/day. Symptom relief with rabeprazole in 8-week trials in patients with GERD was superior to that provided by placebo, and similar to ranitidine or omeprazole. Rabeprazole was similar to omeprazole and superior to placebo in both maintenance of healing and prevention of symptoms in patients with healed GERD in 1-year studies. One-week triple therapy with rabeprazole 20 mg twice daily plus 2 antibacterial agents achieved > or = 90% Helicobacter pylori eradication, but, as would be expected, a regimen of rabeprazole 20 mg twice daily plus 1 antibacterial agent was less successful. The drug was as effective as omeprazole and lansoprazole as part of triple therapy for H. pylori eradication. Rabeprazole successfully reduced acid output to target levels and prevented further pathological changes in 10 patients with Zollinger-Ellison syndrome. Usual dosages of rabeprazole are 20 mg/day for 4 weeks to treat duodenal ulcers, 6 weeks for gastric ulcers and 8 weeks for GERD, although some patients with duodenal ulcer may respond to a 10 mg/day dosage. For long term maintenance of GERD healing, 10 or 20 mg daily doses are adequate. Patients with hypersecretory states may need individualised dosages starting at 60 mg/day. The drug was well tolerated in clinical trials, with headache, rash, infection, diarrhoea and flu syndrome as the most common adverse events. In conclusion, rabeprazole appears to be a well tolerated proton pump inhibitor with a rapid onset of action and a low potential for drug interactions. The drug may be used to achieve healing and the relief of symptoms of duodenal ulcer, gastric ulcer and GERD, maintain GERD healing, and can form part of effective regimens to eradicate H. pylori.

Review article: pharmacokinetic concerns in the selection of anti-ulcer therapy

Rabeprazole is a new, highly potent proton pump inhibitor (PPI) being introduced for the treatment of disorders of gastric acid hypersecretion. Rabeprazole joins other drugs in this class, such as omeprazole, pantoprazole, and lansoprazole, which share a common mechanism of action. Each of these drugs is a substituted benzimidazole, which inhibits activity of the H+, K+ -ATPase located on the apical surface of parietal cells, thereby preventing the secretion of gastric acid. As a result of structural and functional similarities, the PPIs share many pharmacokinetic features. They have comparable rates of absorption, maximum plasma concentrations, and total drug absorptions resulting in similar bioavailability after single-dose administration. With multiple dosing, rabeprazole differs from omeprazole in that its pharmacokinetic profile does not change significantly over the course of therapy. All the PPIs are metabolized rapidly, resulting in short half-lives. However, their duration of activity is much longer, due to the way in which they bind to H+, K+ -ATPase. All are metabolized by hepatic cytochrome P450 enzymes, although only omeprazole has demonstrated significant interactions with other drugs metabolized by this pathway. Rabeprazole, which has a low potential for interacting with drugs metabolized by cytochrome P450, does interfere with the absorption of digoxin and ketoconazole because of its antisecretory effects. The pharmacokinetics of rabeprazole are altered slightly in elderly subjects and in patients with renal and moderate hepatic disease. However, the pharmacokinetic findings suggest that no dosage adjustment is required in these special populations.

Review article: the pharmacokinetics of rabeprazole in health and disease

Rabeprazole, a newly developed proton pump inhibitor, has been shown to be effective for the treatment of gastric and duodenal ulcers and for gastro-oesophageal reflux disease. It is a rapid and potent inhibitor of gastric H+,K(+)-ATPase, the gastric acid (proton) pump. The maximum plasma concentration (Cmax) and the area under the plasma concentration time curve (AUC) are linearly related to dose, while the time to maximum plasma concentration (tmax) and elimination half-life (t1/2) are dose-independent. Rabeprazole is extensively metabolized in the liver via the cytochrome P450 enzyme system, and its metabolites are excreted primarily in the urine. Rabeprazole does not accumulate with repeated dosing. Its bioavailability is not influenced by the coingestion of either food or antacids. The pharmacokinetic profile of rabeprazole is substantially altered in the elderly and patients with stable compensated chronic cirrhosis; however, these alterations are not associated with clinically significant abnormalities in laboratory parameters or serious adverse events. The influence of severe decompensated liver disease on the pharmacokinetics of rabeprazole has not been assessed. The pharmacokinetic profile of rabeprazole is not significantly altered by renal dysfunction requiring maintenance haemodialysis. These findings suggest that dosage adjustment is not required in these special patient populations. Caution should be exercised, however, in patients with severe liver disease.