Genetic polymorphism of CYP2C19 and lansoprazole pharmacokinetics in Japanese subjects

Exploring the impact of ethnicity on drug pharmacokinetics using PBPK models: A case study with lansoprazole in Japanese subjects

AIMS

The aim of this study is to demonstrate the use of PBPK modelling to explore the impact of ethnic differences on drug PK.

METHODS

A PBPK model developed for lansoprazole was used to predict the clinical PK of lansoprazole in Japanese subjects by incorporating the physiological parameters of a Japanese population into the model. Further verification of the developed Japanese population with clinical studies involving eight other CYP substrates-omeprazole, ticlopidine, alprazolam, midazolam, nifedipine, cinacalcet, paroxetine and dextromethorphan-was also carried out.

RESULTS

The PK of lansoprazole in both Caucasian and Japanese subjects was well predicted by the model as the observed data were within the 5th and 95th percentiles across all the clinical studies. In age- and sex-matched simulations in both the Caucasian and Japanese populations, the predicted PK (mean ± SD) of a single oral dose of 30-mg lansoprazole was higher in the Japanese population in all cases, with more than twofold higher AUC of 5.98 ± 6.43 mg/L.h (95% CI: 4.72, 7.24) vs. 2.46 ± 2.45 mg/L.h (95% CI: 1.98, 2.94) in one scenario. In addition, in two out of the nine clinical DDIs of lansoprazole and the additional CYP substrates simulated using the Japanese population, the predicted DDI in Japanese was more than 1.25-fold that in Caucasians, indicating an increased DDI liability.

CONCLUSIONS

By accounting for various physiological parameters that characterize a population in a PBPK model, the impact of the different identified interethnic differences on the drug's PK can be explored, which can inform the adoption of drugs from one region to another.

Differential effects of proton pump inhibitors and vonoprazan on vascular endothelial growth factor expression in cancer cells

Proton pump inhibitors (PPIs) are potent inhibitors of gastric acid secretion, used as first-line agents in treating peptic ulcers. However, we have previously reported that PPIs may diminish the therapeutic effect of anti-vascular endothelial growth factor (VEGF) drugs in patients with cancer. In this study, we explored the effects of vonoprazan, a novel gastric acid secretion inhibitor used for the treatment of peptic ulcers, on the secretion of VEGF in cancer cells and attempted to propose it as an alternative PPI for cancer chemotherapy. The effects of PPI and vonoprazan on VEGF expression in cancer cells were compared by real-time reverse transcription-polymerase chain reaction and ELISA. The interaction of vonoprazan and PPIs with transcriptional regulators by docking simulation analysis. In various cancer cell lines, including the human colorectal cancer cell line (LS174T), PPI increased VEGF messenger RNA expression and VEGF protein secretion, while this effect was not observed with vonoprazan. Molecular docking simulation analysis showed that vonoprazan had a lower binding affinity for estrogen receptor alpha (ER-α), one of the transcriptional regulators of VEGF, compared to PPI. Although the PPI-induced increase in VEGF expression was counteracted by pharmacological ER-α inhibition, the effect of vonoprazan on VEGF expression was unchanged. Vonoprazan does not affect VEGF expression in cancer cells, which suggests that vonoprazan might be an alternative to PPIs, with no interference with the therapeutic effects of anti-VEGF cancer chemotherapy.

The prognosis and incidence of hepatic encephalopathy of patients with liver cirrhosis treated with proton pump inhibitors: A multicenter retrospective study in Japan

Gastrointestinal bleeding, hepatic encephalopathy (HE), and hepatocarcinogenesis are associated with the prognosis of patients with liver cirrhosis (LC). Proton pump inhibitors (PPIs) have been used to prevent bleeding, however the effects of PPIs on overall survival have not yet been elucidated. Therefore, this multicenter retrospective study aimed to assess the effect of PPI on the prognosis and HE occurrence of the patients with liver cirrhosis in Japan.A total of 456 patients diagnosed with LC at the 4 institutes during the study period (2010-2014) were assessed. PPI-treated and non-treated patients were compared using propensity score matching analysis. Primary and secondary endpoints of the study were set as the occurrence of HE and overall survival, respectively.A comparison of all cases showed a significantly poorer hepatic reserve function in the PPI-treated patients. The propensity-score matching analysis was performed and 120 PPI-treated patients were 1:1 matched with non-treated patients. The analysis revealed a higher incidence of HE in the PPI-treated than in the non-treated patients (P = .032; hazard ratio [HR], 2.162; 95% confidence interval [CI], 1.066-4.176), but the prognosis of PPI-treated patients was no worse than that of non-treated patients (P = .676; HR, 1.101; 95% CI, 0.702-1.726).This retrospective study showed that PPI administration for the patients with liver cirrhosis may partly be related to the increased incidence of HE but not worsen the patient prognosis.

Efficacy of vonoprazan for the prevention of bleeding after gastric endoscopic submucosal dissection with continuous use of antiplatelet agents

Background  Post-procedural bleeding, after gastric endoscopic submucosal dissection (ESD) for high risk thromboembolic cases that require continuous antiplatelet therapy, is challenging. Its incidence rate is > 20 % among those using conventional antacids. We evaluated the efficacy of perioperative management with vonoprazan to prevent post-ESD bleeding. Materials and methods  This was a multicenter prospective interventional trial conducted at 10 Japanese referral centers. Patients who regularly used antiplatelet agents (aspirin or thienopyridine derivatives, etc.) and who required continuous antithrombotic medication due to high thromboembolic risk were enrolled. They underwent gastric ESD with continuous aspirin therapy. Oral administration of vonoprazan (20 mg daily) was started from the day of ESD and continued for 28 days. The primary end point was the incidence of post-ESD bleeding. The sample size was 50 patients, and vonoprazan was considered to be effective when the upper threshold of the 95 % confidence interval (CI) for post-ESD bleeding did not exceed 20 %. Results  Although 50 patients were enrolled, one patient withdrew consent. Therefore, 49 patients were included in the analysis. One patient who used aspirin and clopidogrel experienced bleeding 11 days after ESD. The overall post-ESD bleeding rate was 2.0 % (1/49; 95 %CI 0.4-10.7 %). Thromboembolic events were not observed. One case of ESD-associated adverse events (perforation) and one case of drug-associated adverse events (drug eruption, possibly due to vonoprazan) were observed. Conclusions  Vonoprazan may be efficacious for preventing post-ESD bleeding in patients using continuous antiplatelet therapy, warranting further comparative study to definitively test the effectiveness of the drug.

Hypergastrinemia in Long-Term Use of Proton Pump Inhibitors

BACKGROUND/AIM

The use of proton pump inhibitors (PPIs) is known to lead to hypergastrinemia; however, the data in patients with atrophic gastritis is still lacking. The aim of this study was to investigate the effects of long-term PPIs use on the gastrin levels in patients with atrophic gastritis and to determine factors affecting hypergastrinemia in long-term users of PPIs.

METHODS

Serum Helicobacter pylori IgG, gastrin and pepsinogen levels were measured. Atrophic gastritis was assessed by upper gastrointestinal endoscopies based on the Kimura-Takemoto classification and pepsinogen levels. CYP2C19 polymorphisms were assessed using DNA extracted from peripheral blood.

RESULTS

A total number of 382 patients (275 men and 107 women) were enrolled. Median serum gastrin levels were higher in PPI users than in non- users (234 vs. 113 pg/mL, p < 0.001) and in women than in men (252 vs. 155 pg/mL, p = 0.006). Gastrin levels were significantly associated with corpus atrophy only in the subgroup of non-users of PPIs. Multivariate analysis revealed that hypergastrinemia (over 150 pg/mL) was significantly associated with PPI use (OR 5.30; 95% CI 3.32-8.47), women (OR 2.22; 95% CI 1.33-3.72) and corpus atrophy (OR 1.82; 95% CI 1.14-2.90).

CONCLUSION

PPI use, women and corpus atrophy were risk factors for hypergastrinemia. Gender, but not corpus atrophy, affected the gastrin levels in long-term users of PPIs.

Limited Effect of Rebamipide in Addition to Proton Pump Inhibitor (PPI) in the Treatment of Post-Endoscopic Submucosal Dissection Gastric Ulcers: A Randomized Controlled Trial Comparing PPI Plus Rebamipide Combination Therapy with PPI Monotherapy

Background/Aims

The ability of endoscopic submucosal dissection (ESD) to resect large early gastric cancers (EGCs) results in the need to treat large artificial gastric ulcers. This study assessed whether the combination therapy of rebamipide plus a proton pump inhibitor (PPI) offered benefits over PPI monotherapy.

Methods

In this prospective, randomized, multicenter, open-label, and comparative study, patients who had undergone ESD for EGC or gastric adenoma were randomized into groups receiving either rabeprazole monotherapy (10 mg/day, n=64) or a combination of rabeprazole plus rebamipide (300 mg/day, n=66). The Scar stage (S stage) ratio after treatment was compared, and factors independently associated with ulcer healing were identified by using multivariate analyses.

Results

The S stage rates at 4 and 8 weeks were similar in the two groups, even in the subgroups of patients with large amounts of tissue resected and regardless of CYP2C19 genotype. Independent factors for ulcer healing were circumferential location of the tumor and resected tissue size; the type of treatment did not affect ulcer healing.

Conclusions

Combination therapy with rebamipide and PPI had limited benefits compared with PPI monotherapy in the treatment of post-ESD gastric ulcer (UMIN Clinical Trials Registry, UMIN000007435).

Influence of Proton Pump Inhibitors on Mycophenolic Acid Pharmacokinetics in Patients With Renal Transplantation and the Relationship With Cytochrome 2C19 Gene Polymorphism

BACKGROUND

Most patients have serious digestive complications after renal transplantation. Therefore, it is important to protect gastrointestinal function to improve the survival rate of transplant patients. Proton pump inhibitors (PPIs) such as lansoprazole and rabeprazole are widely administered to renal transplant patients with mycophenolic acid (MPA) in the perioperative period. PPIs are metabolized by cytochrome (CYP) 2C19 enzymes. Mycophenolate sodium (MYF) and mycophenolate mofetil (MMF) have been used in immunosuppression. Clinically relevant drug-drug interactions have been described between immunosuppressive drugs. In the present study, we investigated the drug interaction between MPA and lansoparazole or rabeprazole and the impact of CYP2C19 polymorphisms on these drug interactions after renal transplantation.

MATERIALS AND METHODS

A total of 125 renal transplant patients taking MPA derivatives between 2012 and 2016 were included in this study. The 125 patients were divided into 6 groups: MMF/tacrolimus/steroid together with lansoprazole or rabeprazole; MYF/tacrolimus/steroid together with lansoprazole or rabeprazole and without PPI. The single nucleotide polymorphisms of CYP2C19 were determined by the polymerase chain reaction-restriction fragment length polymorphism. Plasma concentrations of MPA were measured by cloned enzyme donor immunoassay. Clinical parameters such as incidence of delayed graft function and acute rejection, the rate of change of serum creatinine, toxicity, and gastrointestinal adverse effects were analyzed retrospectively.

RESULTS

The mean concentrations of MPA in the MYF group were higher than those in the MMF group. The mean dose-adjusted blood concentration of MPA coadministered with lansoprazole was lower than that of MPA with rabeprazole or without PPI in MMF and MYF groups (P < .05). In patients with the CYP2C19*2/*2 genotype, the mean concentrations of MMF with lansoprazole were significantly lower than those with rabeprazole with MMF or without PPI (P < .05). Gastrointestinal side effects were significantly higher in MMF with lansoprazole group than in MYF with lansoprazole group (P < .05). However, no differences were found according to genotype distribution in all groups (P > .05).

CONCLUSION

Polymorphisms in CYP2C19 are related to the metabolic oxidation of drugs to varying degrees. Both genetic and clinical factors in pharmacokinetics may help to make further progress toward individualized therapy to yield maximum efficacy with minimal side effects.

Lansoprazole Exacerbates Pemetrexed-Mediated Hematologic Toxicity by Competitive Inhibition of Renal Basolateral Human Organic Anion Transporter 3

Pemetrexed, a multitargeted antifolate, is eliminated by tubular secretion via human organic anion transporter 3 (hOAT3). Although proton pump inhibitors (PPIs) are frequently used in cancer patients, the drug interaction between PPIs and pemetrexed remains to be clarified. In this study, we examined the drug interaction between pemetrexed and PPIs in hOAT3-expressing cultured cells, and retrospectively analyzed the impact of PPIs on the development of hematologic toxicity in 108 patients who received pemetrexed and carboplatin treatment of nonsquamous non-small cell lung cancer for the first time between January 2011 and June 2015. We established that pemetrexed was transported via hOAT3 (Km = 68.3 ± 11.1 µM). Lansoprazole, rabeprazole, pantoprazole, esomeprazole, omeprazole, and vonoprazan inhibited hOAT3-mediated uptake of pemetrexed in a concentration-dependent manner. The inhibitory effect of lansoprazole was much greater than those of other PPIs and the apparent IC50 value of lansoprazole against pemetrexed transport via hOAT3 was 0.57 ± 0.17 µM. The inhibitory type of lansoprazole was competitive. In a retrospective study, multivariate analysis revealed that coadministration of lansoprazole, but not other PPIs, with pemetrexed and carboplatin was an independent risk factor significantly contributing to the development of hematologic toxicity (odds ratio: 10.004, P = 0.005). These findings demonstrated that coadministration of lansoprazole could exacerbate the hematologic toxicity associated with pemetrexed, at least in part, by competitive inhibition of hOAT3. Our results would aid clinicians to make decisions of coadministration drugs to avoid drug interaction-induced side effects for achievement of safe and appropriate chemotherapy with pemetrexed.

Stereoselective binding of chiral drugs to plasma proteins

Chiral drugs show distinct biochemical and pharmacological behaviors in the human body. The binding of chiral drugs to plasma proteins usually exhibits stereoselectivity, which has a far-reaching influence on their pharmacological activities and pharmacokinetic profiles. In this review, the stereoselective binding of chiral drugs to human serum albumin (HSA), α1-acid glycoprotein (AGP) and lipoprotein, three most important proteins in human plasma, are detailed. Furthermore, the application of AGP variants and recombinant fragments of HSA for studying enantiomer binding properties is also discussed. Apart from the stereoselectivity of enantiomer-protein binding, enantiomer-enantiomer interactions that may induce allosteric effects are also described. Additionally, the techniques and methods used to determine drug-protein binding parameters are briefly reviewed.

CYP2C19- and CYP3A4-Dependent Omeprazole Metabolism in West Mexicans

Omeprazole has been used as a drug probe for CYP2C19, but no systematic data are available for Mexican populations. The aim of this study was to evaluate the phenotype frequencies of the CYP2C19 polymorphism in West Mexicans. Besides omeprazole, sulfone was measured to evaluate CYP3A4 after administration of the 20-mg dose to 127 healthy volunteers. Logarithms of metabolic indexes of omeprazole/hydroxyomeprazole for CYP2C19 and omeprazole/omeprazole sulfone for CYP3A4 had trimodal distributions. Five subjects (4%) had a log CYP2C19 metabolic index below -0.9, suggesting an ultra-extensive phenotype. Poor metabolizers (log metabolic index > 0.6) were 6%. For CYP3A4, 11 subjects (9%) were below -0.3 of the log metabolic index. The log metabolic index of omeprazole/omeprazole sulfone was above the antimode of 0.6 for 11% of this population. The mean log metabolic index of CYP3A4 extensive metabolizers (80%) was 0.166, which seems to be higher than the data described for Caucasians and lower than that for Asians.

Genetic Polymorphisms of Cytochrome P450 Enzymes and the Effect on Interindividual, Pharmacokinetic Variability in Extensive Metabolizers

Genetic polymorphisms of cytochrome P450 (CYP) enzymes are one of the factors that contribute to the pharmacokinetic (PK) variability of drugs. PK variability is observed in the bimodal distribution between extensive metabolizers (EMs) and poor metabolizers (PMs). PK variability may also exist between individuals genotyped as homozygous EMs and heterozygous EMs. This may carry implications for drug dosing and drug response (e.g., risk of therapeutic failure or drug toxicity). Studies have reported significant PK differences between homozygous and heterozygous EMs. Some literature suggests that this distinction may be of clinical relevance. Due to study design limitations and data that are either sparse or conflicting, generalizations regarding the potential impact of the CYP genotype, within EMs, are difficult. Optimally designed clinical trials are needed. This review evaluates the potential impact of CYP genetic polymorphisms on interindividual PK variability of drugs within an EM population.

In vivo quantitative prediction of the effect of gene polymorphisms and drug interactions on drug exposure for CYP2C19 substrates

We present a unified quantitative approach to predict the in vivo alteration in drug exposure caused by either cytochrome P450 (CYP) gene polymorphisms or CYP-mediated drug-drug interactions (DDI). An application to drugs metabolized by CYP2C19 is presented. The metrics used is the ratio of altered drug area under the curve (AUC) to the AUC in extensive metabolizers with no mutation or no interaction. Data from 42 pharmacokinetic studies performed in CYP2C19 genetic subgroups and 18 DDI studies were used to estimate model parameters and predicted AUC ratios by using Bayesian approach. Pharmacogenetic information was used to estimate a parameter of the model which was then used to predict DDI. The method adequately predicted the AUC ratios published in the literature, with mean errors of -0.15 and -0.62 and mean absolute errors of 0.62 and 1.05 for genotype and DDI data, respectively. The approach provides quantitative prediction of the effect of five genotype variants and 10 inhibitors on the exposure to 25 CYP2C19 substrates, including a number of unobserved cases. A quantitative approach for predicting the effect of gene polymorphisms and drug interactions on drug exposure has been successfully applied for CYP2C19 substrates. This study shows that pharmacogenetic information can be used to predict DDI. This may have important implications for the development of personalized medicine and drug development.

Pharmacokinetics of lansoprazole and its main metabolites after single and multiple intravenous doses in healthy Chinese subjects

The aim of the study was to evaluate and compare the pharmacokinetics of lansoprazole (LPZ) and its main metabolites, 5'-hydroxy lansoprazole (HLPZ) and lansoprazole sulfone (LPZS), after single and multiple intravenous (i.v.) doses of LPZ in healthy Chinese subjects. Twelve subjects (six males and six females) were given a single dose of LPZ by i.v. infusion on day 1, and multiple doses from day 2 to day 6. Blood samples were collected at designated time points for analysis of plasma concentrations of LPZ, HLPZ and LPZS by an LC-MS/MS method. LPZ was generally well tolerated in healthy Chinese subjects. After single and multiple i.v. doses of 30 mg LPZ, the C max values of LPZ, HLPZ and LPZS were 1490 ± 290 and 1450 ± 280, 175 ± 71 and 154 ± 56, and 51.3 ± 82.9 and 74.1 ± 158.7 ng/mL, with the AUC0-t values 3280 ± 2550 and 4260 ± 3880, 381 ± 128 and 389 ± 111, and 389 ± 1204 and 700 ± 2255 ng h/mL, respectively. The t 1/2 and CL values of LPZ after single and multiple i.v. doses were 1.48 ± 1.03 and 2.19 ± 1.03 h, and 11.67 ± 4.49 and 9.56 ± 4.08 L/h, respectively. Compared with the pharmacokinetics of LPZ after a single dose, t 1/2 increased markedly, CL decreased significantly and AUC increased by over 20 % after multiple doses. The results indicated that there was drug accumulation of LPZ after multiple i.v. doses, and there was no gender-related difference in pharmacokinetics of LPZ and its two metabolites.

Pharmacokinetics of lansoprazole and its main metabolites after single intravenous doses in healthy Chinese subjects

The aim of the study was to evaluate the pharmacokinetics (PK) of lansoprazole (LPZ) and its main metabolites 5'-hydroxy lansoprazole (HLPZ) and lansoprazole sulphone (LPZS) after single intravenous (i.v.) doses of LPZ in healthy Chinese subjects, and the relationship between the cytochrome P450 (CYP) 2C19 phenotypes and the plasma concentrations of LPZS at the time-points in the elimination phase of LPZ. Twelve subjects were given lansoprazole by i.v. infusion. Blood samples were collected at designated time points up to 24 h. Plasma concentrations of LPZ, HLPZ and LPZS were quantified by a selective and sensitive liquid chromatography-tandem mass spectrometric (LC-MS/MS) method. After single i.v. doses of 15, 30 and 60 mg LPZ, C(max) and area under the plasma concentration-time curve (AUC(0-t)) of LPZ were 725 ± 151, 1480 ± 190, 3130 ± 480 µg · L(-1) and 1690 ± 1210, 3630 ± 2530, 8080 ± 4550 µg · h · L(-1), respectively. LPZ was generally well tolerated in healthy Chinese subjects, and displayed linear PK in the range of 15-60 mg. There were significant differences in the elimination of LPZ and the formation of LPZS between the single CYP2C19 poor metabolizer (PM) and the CYP2C19 extensive metabolizers (EM). The concentration of LPZS at the time-points in the elimination phase of LPZ could be monitored for CYP2C19 phenotyping. As a probe drug for CYP2C19 phenotyping, LPZ for injection might be more suitable than LPZ oral formulations.

Influence of CYP2C19 and ABCB1 polymorphisms on plasma concentrations of lansoprazole enantiomers after enteral administration

An intraoral annihilation enteric-coated preparation of lansoprazole is often administered via intestinal fistula. The purpose of this study was to determine the plasma concentrations of lansoprazole enantiomers after enteral administration in subjects with cytochrome P4502C19 (CYP2C19) and ABCB1 C3435T genotypes. Fifty-one patients who underwent a curative oesophagectomy for oesophageal cancer were enrolled in this study. After a single enteral dose of racemic lansoprazole (30 mg), plasma concentrations of lansoprazole enantiomers were measured 4 h post-dose (C(4h)). There were significant differences in the C(4h) of (R)- and (S)-lansoprazole and the R/S-enantiomer ratio for three CYP2C19 genotype groups (*1/*1, *1/*2 ± *1/*3, and *2/*2 ± *2/*3 ± *3/*3 (poor metabolizers (PMs)), but not the ABCB1 C3435T genotypes. In a stepwise forward selection multiple regression analysis, the C(4h) of (R)- and (S)-lansoprazole were associated with CYP2C19 PMs (p = 0.0005 and < 0.0001 respectively) and age (p = 0.0040 and 0.0121 respectively), while the R/S-enantiomer ratio was associated with CYP2C19*1/*1 (p = 0.0191) and CYP2C19 PMs (p = 0.0426). Direct administration to the jejunum is unaffected by residence time in the stomach and the gastric emptying rate. With enteral administration, CYP2C19 phenotyping of patients using the lansoprazole R/S enantiomer index at C(4h) could be possible.

Functional characterization of two novel CYP2C19 variants (CYP2C19*18andCYP2C19*19) found in a Japanese population

Cytochrome P450 2C19 (CYP2C19) plays an important role in the metabolism of a wide range of therapeutic drugs and exhibits genetic polymorphism with interindividual differences in metabolic activity. We have previously described two CYP2C19 allelic variants, namely CYP2C19*18 and CYP2C19*19 with Arg329His/Ile331Val and Ser51Gly/Ile331Val substitutions, respectively. In order to investigate precisely the effect of amino acid substitutions on CYP2C19 function, CYP2C19 proteins of the wild-type (CYP2C19.1B having Ile331Val) and variants (CYP2C19.18 and CYP2C19.19) were heterologously expressed in yeast cells, and their S-mephenytoin 4'-hydroxylation activities were determined. The K(m) value of CYP2C19.19 for S-mephenytoin 4'-hydroxylation was significantly higher (3.0-fold) than that of CYP2C19.1B. Although no significant differences in V(max) values on the basis of microsomal and functional CYP protein levels were observed between CYP2C19.1B and CYP2C19.19, the V(max)/K(m) values of CYP2C19.19 were significantly reduced to 29-47% of CYP2C19.1B. By contrast, the K(m), V(max) or V(max)/K(m) values of CYP2C19.18 were similar to those of CYP2C19.1B. These results suggest that Ser51Gly substitution in CYP2C19.19 decreases the affinity toward S-mephenytoin of CYP2C19 enzyme, and imply that the genetic polymorphism of CYP2C19*19 also causes variations in the clinical response to drugs metabolized by CYP2C19.

Pharmacokinetic properties of lansoprazole (30-mg enteric-coated capsules) and its metabolites: A single-dose, open-label study in healthy Chinese male subjects

BACKGROUND

Lansoprazole, a benzimidazole derivative, is indicated for the treatment of various peptic diseases. It is metabolized mainly in the liver, and its primary active metabolites present in plasma are 5'-hydroxy lansoprazole and lansoprazole sulfone. Few data are available on the pharmacokinetic properties of lansoprazole, 5'-hydroxy lansoprazole, and lansoprazole sulfone, which can be used to measure cytochrome P450 (CYP) 2C19 activity.

OBJECTIVES

The aims of this study were to investigate the clinical plasma pharmacokinetic properties of lansoprazole and its metabolites in healthy Chinese male volunteers, and to assess the influences of CYP2C19 on the pharmacokinetics of lansoprazole.

METHODS

Healthy adult Chinese male volunteers were enrolled in this single-dose, open-label study. All patients received a single oral enteric capsule containing 30 mg of lansoprazole after a 12-hour overnight fast. Serial blood samples were collected immediately before (0 hour) and at 20, 40, 60, 90, 120, and 150 minutes and 3, 4, 6, 8, 10, 12, 15, and 24 hours after study drug administration. The plasma concentrations of lansoprazole, 5'-hydroxy lansoprazole, and lansoprazole sulfone were determined using a validated internal standard high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) method. Pharmacokinetic properties (including Cmax, Tmax, elimination t½ [t½z], mean residence time [MRT], AUC0-24, AUC0-∞, apparent oral clearance [CLz/F], and apparent volume of distribution [Vz/F]) were determined using the noncompartmental method.

RESULTS

Twenty volunteers (mean [SD] age, 34.9 [2.9] years; weight, 64.6 [2.2] kg; height, 171.3 [3.3] cm) were enrolled in and completed the study. The mean (SD) pharmacokinetic properties of lansoprazole were as follows: Cmax, 1047 (344) ng/mL; Tmax, 2.0 (0.7) hours; t½z, 2.24 (1.43) hours; MRT, 3.62 (0.87) hours; AUC0-24, 3388 (1484) ng/mL/h; AUC0-∞, 3496 (1693) ng/mL/h; CLz/F, 9.96 (3.74) L/h; and Vz/F, 32.83 (11.74) L. The findings with 5'-hydroxy lansoprazole and lansoprazole sulfone, respectively, were as follows: Cmax, 111.2 (41.8) and 66.6 (52.9) ng/mL; Tmax, 2.1 (0.8) and 1.9 (0.8) hours; t½z, 2.31 (1.18) and 2.52 (1.54) hours; and AUC0-24, 317.0 (81.2) and 231.9 (241.7) ng/mL/h. No adverse events were reported throughout the study.

CONCLUSIONS

In these healthy Chinese male volunteers administered a single oral dose of lansoprazole 30 mg, absorption of lansoprazole was rapid (mean Cmax, 1047 ng/mL; Tmax, ~2.0 hours). Its 2 primary active metabolites, 5'-hydroxy lansoprazole and lansoprazole sulfone, were identified in measurable quantities in plasma (Cmax, 111.2 and 66.6 ng/mL, respectively; and Tmax, 2.1 and 1.9 hours). The plasma t½z did not appear to reflect the duration of suppression of gastric acid secretion: the t½z values of lansoprazole and the 2 metabolites were ~2 to 2.5 hours, while the acid-inhibitory effect lasted >24 hours. Cmax, AUC, and t½z of lansoprazole, and especially lansoprazole sulfone, varied. Differences in metabolism types and/or genotype of CYP2C19 should be taken into account when planning a lansoprazole dosing regimen.

Identification and relative contributions of human cytochrome P450 isoforms involved in the metabolism of glibenclamide and lansoprazole: evaluation of an approach based on thein vitrosubstrate disappearance rate

1. The identification and relative contributions of human cytochrome P450 (CYP) enzymes involved in the metabolism of glibenclamide and lansoprazole in human liver microsomes were investigated using an approach based on the in vitro disappearance rate of unchanged drug. 2. Recombinant CYP2C19 and CYP3A4 catalysed a significant disappearance of both drugs. When the contribution of CYPs to the intrinsic clearance (CL(int)) of drugs in pooled human microsomes was estimated by relative activity factors, contributions of CYP2C19 and CYP3A4 were determined to be 4.6 and 96.4% for glibenclamide, and 75.1 and 35.6% for lansoprazole, respectively. 3. CL(int) of glibenclamide correlated very well with CYP3A4 marker activity, whereas the CL(int) of lansoprazole significantly correlated with CYP2C19 and CYP3A4 marker activities in human liver microsomes from 12 separate individuals. Effects of CYP-specific inhibitors and anti-CYP3A serum on the CL(int) of drugs in pooled human liver microsomes reflected the relative contributions of CYP2C19 and CYP3A4. 4. The results suggest that glibenclamide is mainly metabolized by CYP3A4, whereas lansoprazole is metabolized by both CYP2C19 and CYP3A4 in human liver microsomes. This approach, based on the in vitro drug disappearance rate, is useful for estimating CYP identification and their contribution to drug discovery.

Intestinal CYP3A4 is not involved in the enantioselective disposition of lansoprazole

The contribution of (S)-lansoprazole to CYP3A4-catalysed sulfoxidation is greater than that of (R)-lansoprazole. The aim was to investigate the effect of grapefruit juice on the enantioselective disposition of lansoprazole among three CYP2C19 genotype groups. Eighteen healthy subjects, consisting of six each of homozygous extensive metabolizers (homEMs), heterozygous extensive metabolizers (hetEMs) and poor metabolizers (PMs), ingested a single oral dose of 60 mg racemic lansoprazole after taking either 200 ml grapefruit juice or water. There was no effect of grapefruit juice on the mean maximum plasma concentrations (C(max)) or the elimination half-life for each lansoprazole enantiomer in all three CYP2C19 genotype groups. Similarly, the pharmacokinetic parameters of lansoprazole sulfone remained unaltered by grapefruit juice in all three groups. The CYP3A4-mediated first-pass sulfoxidation of (R)- and (S)-lansoprazole were not influenced by grapefruit juice. In addition, stereoselectivity of the intestinal CYP3A4-catalysed sulfoxidation of (R)- and (S)-lansoprazole was not observed.

Simultaneous determination of lansoprazole and its metabolites 5'-hydroxy lansoprazole and lansoprazole sulphone in human plasma by LC-MS/MS: application to a pharmacokinetic study in healthy volunteers

A highly sensitive and specific liquid chromatography coupled with tandem mass spectrometric (LC-MS/MS) method has been developed and validated for the simultaneous determination of lansoprazole and its metabolites 5'-hydroxy lansoprazole and lansoprazole sulphone. The detection was operated with multiple reaction-monitoring (MRM) using the electrospray ionization technique. The assay procedure involved precipitation of plasma samples with acetonitrile after indapamide was added as internal standard (IS). The chromatographic separation was achieved with a mixture of methanol-0.2% ammonium acetate and 0.1% methanoic acid in water (75:25, v/v) as mobile phase on an Inertsil ODS-3 column. The method was proved to be accurate and precise with linearity ranges of 10-4,000 ng/ml, 5.0-400 ng/ml, and 1.0-400 ng/ml for lansoprazole, 5'-hydroxy lansoprazole and lansoprazole sulphone, respectively, with the correlation coefficients (r) better than 0.999. The lower limits of quantification (LLOQ) were 2.0 ng/ml, 2.0 ng/ml, and 0.5 ng/ml for lansoprazole, 5'-hydroxy lansoprazole and lansoprazole sulphone, respectively. The intra- and inter-day precision and accuracy values were found to be within the assay variability limits (R.S.D.% within +/-15) in accordance with FDA guidelines. The validated LC-MS/MS method has been successfully applied for the determination of lansoprazole and its metabolites in human plasma.

Influence of lansoprazole and rabeprazole on mycophenolic acid pharmacokinetics one year after renal transplantation

Peptic ulcer disease is a common complication after organ transplantation, and long-term administration of antiulcer agents is needed in many renal transplant recipients. Although several drug interactions with mycophenolic acid (MPA), the active metabolite of the prodrug mycophenolate mofetil (MMF), have been reported, little is known about the interaction between MPA and proton pump inhibitors (PPIs). The present study investigated the drug interaction between MMF and lansoprazole or rabeprazole and the impact of cytochrome (CYP) 2C19, and multidrug resistance (MDR)1 C3435T polymorphisms on these drug interactions at 1 year after renal transplantation. Retrospectively, 61 recipients were divided into 3 groups: MMF and tacrolimus as combination immunosuppressive therapy, together with either 30 mg lansoprazole (n = 22) or 10 mg rabeprazole (n = 17), or without PPI (n = 22). One year after transplantation, plasma concentrations of MPA were measured by high-performance liquid chromatography. The mean dose-unadjusted and -adjusted Cmax of MPA with 30 mg lansoprazole were significantly lower than those without PPI (11.8 vs. 17.8 microg/mL, P = 0.0197, and 22.6 vs. 33.1 ng/mL/mg MMF, P = 0.0222, respectively). In recipients having the CYP2C19 *1/*2+*1/*3 or MDR1 C3435T CC genotype, the mean dose-adjusted AUC0-12 of MPA with 30 mg lansoprazole was significantly smaller than that with 10 mg rabeprazole or without PPI. The plasma concentration of MPA was influenced by 30 mg lansoprazole but not 10 mg rabeprazole. Because of the greater gastric acid secretion-inhibitory effect of 30 mg lansoprazole in recipients having the CYP2C19 *1/*2+*1/*3 (intermediate metabolizer) or MDR1 C3435T CC genotype, the elution and hydrolysis of MMF might be decreased. Although the clinical relevance might be minor, the fact that administration of 30 mg lansoprazole in patients having the CYP2C19 *2 or *3 allele or the MDR1 C3435T CC genotype diminishes the absorption of MPA in the maintenance stage after renal transplantation should be taken into consideration with regard to the MPA pharmacokinetics.

Distinct effects of omeprazole and rabeprazole on the tacrolimus blood concentration in a kidney transplant recipient

Proton-pump inhibitors (PPIs, e.g. omeprazole and rabeprazole) are often administered to transplant patients as a treatment or prophylaxis for ulcers after surgery. Since tacrolimus and PPIs share the CYP3A4 system for metabolism, pharmacokinetic interactions are anticipated when they are administered simultaneously. We present a Japanese male patient who underwent a living-donor kidney transplantation having received tacrolimus, mycophenolate mofetil, and prednisolone for immunosuppression. The concentration/dose (C/D) ratio for tacrolimus was markedly higher during the period of treatment with omeprazole than ranitidine or rabeprazole. The results of liver functional tests were within the normal range during the use of these three antacid drugs. Since the higher C/D ratio for tacrolimus when omeprazole was being administered did not result from a decrease in the elimination of tacrolimus due to hepatic dysfunction, drug interaction between omeprazole and tacrolimus was strongly suspected. The present case indicates that rabeprazole can be used safely in place of omeprazole in kidney transplant recipients receiving tacrolimus.

Influence of rabeprazole and lansoprazole on the pharmacokinetics of tacrolimus in relation to CYP2C19, CYP3A5 and MDR1 polymorphisms in renal transplant recipients

The objective of this study was to evaluate whether genetic polymorphisms of CYP2C19, CYP3A5 and MDR1 significantly impact the interaction between tacrolimus and rabeprazole or lansoprazole. Seventy-three recipients were randomly assigned after renal transplantation to receive repeated doses of tacrolimus for 28 days with a regimen of either 20 mg of rabeprazole or 30 mg of lansoprazole. Blood concentrations of tacrolimus were measured by microparticle enzyme immunoassay. The mean daily dose and the dose-adjusted area under the plasma concentration-time curves from 0 to 12 h (AUC(0-12)) of tacrolimus coadministered with rabeprazole or lansoprazole were the lowest and highest, respectively, in CYP2C19 poor metabolizers (PMs) having the CYP3A5*3/*3 genotype (0.084 and 0.112 mg/kg/day and 1.269 and 1.033 ng.h/ml/mg/kg, respectively). On the other hand, the mean dose-adjusted AUC(0-12) of tacrolimus coadministered with rabeprazole or lansoprazole were the highest in CYP2C19 PMs having the MDR13435CC+CT genotype, but not significantly. The present study indicates that there are significant interactions between tacrolimus and rabeprazole or lansoprazole in CYP2C19 PM renal transplant recipients bearing the CYP3A5*3/*3 genotypes. For recipients having these genetic polymorphisms, lower dosages of tacrolimus are required to achieve the target therapeutic index.

Influence of Cytochrome P450 (CYP)??3A5 Polymorphisms on the Pharmacokinetics of Lansoprazole Enantiomers in CYP2C19 Extensive Metaboliser Renal Transplant Recipients

BACKGROUND AND OBJECTIVE

Lansoprazole is extensively metabolised by cytochrome P450 (CYP) 2C19 and CYP3A4. The purpose of this study was to evaluate the effects of CYP3A5 polymorphism (A6986G) on the pharmacokinetics of lansoprazole enantiomers in renal transplant recipients who are CYP2C19 extensive metabolisers (EMs).

METHODS

Among 40 Japanese CYP2C19 EMs, 20 had the CYP3A5*1 allele (*1/*1 in two subjects and *1/*3 in 18 subjects) and 20 had the CYP3A5*3/*3 genotype. After repeated oral doses of racemic lansoprazole 30mg once daily for 28 days, plasma concentrations of lansoprazole enantiomers were determined using high performance liquid chromatography.

RESULTS

The mean area under the plasma concentration-time curves from 0 to infinity (AUC(infinity)) of (R)- and (S)-lansoprazole in recipients with the CYP3A5*1 allele were 3145 and 384 ng * h/mL, respectively, compared with 4218 and 587 ng * h/mL in recipients with the CYP3A5*3/*3 genotype. The AUC(infinity) and the maximum plasma concentration of (R)- and (S)-lansoprazole in subjects with the CYP3A5*3/*3 genotype were greater than subjects with CYP3A5*1/*1 + *1/*3 alleles. The mean R/S ratio for AUC of lansoprazole in each CYP3A5 genotype group was the same (12.6).

CONCLUSION

Our findings show that CYP3A5 genotype is not an important determinant of enantioselective disposition of lansoprazole. Based on our results and those of previous studies, the enantioselective disposition of lansoprazole appears to be primarily influenced by enantioselective metabolism by CYP2C19 rather than by CYP3A.

Genetic variations and haplotypes of CYP2C19 in a Japanese population

Forty-eight single nucleotide variations, including 27 novel ones, were found in the 5'- regulatory region, all of the exons and their surrounding introns of CYP2C19 in 253 Japanese subjects (134 diabetic patients and 119 healthy volunteers). Identified novel variations were as follows: -2772G>A, 2767_-2760delGGTGAACA, -2720T>C, -2547delG, -2545G>T, -2545_-2544 delGC, and -2040C>T in the enhancer region; -778C>T, -777G>A, -529G>C, -189C>A, and -185A>G in the promoter region; 151A>G (S51G), 481G>C (A161P), 986G>A (R329H), 1078G>A (D360N), and 1119C>T (D373D) in the exons, and IVS1+128T>A, IVS3+163G>A, IVS4+271A>G, IVS5-49A>G, IVS6-210C>T, IVS6-196T>A, IVS6-32T>A, IVS7+84G>A, IVS7-174C>T, and IVS8+64C>T in the introns. Since we found no significant differences in the variation frequencies between healthy volunteers and diabetic patients, the data for all subjects were treated as one group in further analysis. The allele frequencies were 0.265 for IVS6-196T>A, 0.045 for -2772G>A and -2720T>C, 0.024 for -2040C>T, 0.014 for IVS7-174C>T, 0.010 for -529G>C, 0.006 for IVS1+128T>A and 481G>C (A161P), 0.004 for -2767_-2760delGGTGAACA and IVS6-210C>T, and 0.002 for the other 17 variations. In addition, the two known nonsynonymous single nucleotide polymorphisms, 681G>A (splicing defect, (*)2 allele) and 636G>A (W212X; (*)3 allele) were detected at 0.267 and 0.128 frequencies, respectively. No variation was detected in the known binding sites for constitutive androstane receptor and glucocorticoid receptor. Linkage disequilibrium analysis showed several close linkages of variations throughout the gene. By using the variations, thirty-one haplotypes of CYP2C19 and their frequencies were estimated. Our results would provide fundamental and useful information for genotyping CYP2C19 in the Japanese and probably other Asian populations.

Enantioselective Disposition of Lansoprazole and Rabeprazole in Human Plasma

Lansoprazole is extensively metabolized by CYP2C19 and CYP3A4 in the liver, whereas rabeprazole is primarily converted non-enzymatically to rabeprazole-thioether, with only some being oxidized by CYP2C19 and CYP3A4. Lansoprazole and rabeprazole possess asymmetric sulfur in their chemical structure and have typically been used clinically as a racemic mixture. This article reviews the pharmacokinetic differences between enantiomers of lansoprazole and rabeprazole in relation to the CYP2C19 genotypes. In our studies in healthy Japanese subjects, the magnitude of contribution of each lansoprazole enantiomer for CYP2C19 was greater than that for CYP3A4. CYP2C19 influenced the disposition of (S)-lansoprazole to a greater extent than the (R)-enantiomer. The R/S ratios for the AUC of lansoprazole in CYP2C19 homEMs, hetEMs and PMs was 12.7, 8.5 and 5.8, respectively. On the other hand, (R)-rabeprazole disposition was influenced to a greater degree by CYP2C19 genetic polymorphisms than (S)-rabeprazole. However, the R/S ratios for the AUC of rabeprazole in CYP2C19 homEMs, hetEMs and PMs was only 1.8, 2.2 and 2.4, respectively, suggesting a lesser effect of CYP2C19 polymorphisms on the stereoselective disposition of rabeprazole compared to lansoprazole. Such a difference in the AUC between rabeprazole enantiomers is likely to be dependent on stereoselectivity in the CYP3A4-mediated metabolic conversion from rabeprazole-thioether to rabeprazole. Both enantiomers of these PPIs have been reported to possess equal potency. Therefore, particularly with lansoprazole, the use of (R)-lansoprazole alone would be highly desirable for use in clinical applications.

Papel del polimorfismo genético CYP2C19 en los efectos adversos a fármacos y en el riesgo para diversas enfermedades

There are a great number of polymorphic genes in the human genome. Many of them codify enzymes that metabolizes drugs and xenobiotic agents, including carcinogens. Among the better known of them, there are a number of isozymes of the microsomal oxidative system (CYP3A4, CYP2C9, CYP2C19 y CYP2D6). This article reviews the following issues: a) frequency of presentation of the "poor metabolizer" genotype and/or phenotype for substrates of CYP2C19; b) role of CYP2C19 polymorphism on the metabolism of some drugs (mephenytoine and other antiepileptic drugs, proton pump inhibitors, several antidepressants and anxyolitics, the antimalaria aggent proguanyl, and propranolol, among others, use this metabolic pathway), and c) possible role of CYP2C19 polymorphism in the risk for development of neoplasia and other diseases (systemic lupus erythematosus, psoriasis, hip osteonecrosis, Alzheimer's disease, amyotrophic lateral sclerosis, essential tremor).

Enantioselective disposition of lansoprazole in relation to CYP2C19 genotypes in the presence of fluvoxamine

AIMS

Lansoprazole is affected by polymorphism of CYP2C19. The aim of this study was to examine the effects of fluvoxamine, a CYP2C19 inhibitor, on the pharmacokinetics of each lansoprazole enantiomer among three different CYP2C19 genotype groups.

METHODS

Eighteen healthy subjects, of whom six each were homozygous extensive metabolizers (homEMs), heterozygous extensive metabolizers (hetEMs), or poor metabolizers (PMs) for CYP2C19, participated in the study. Each subject received either placebo or fluvoxamine, 25 mg twice daily for 6 days, then a single oral dose of 60 mg of racemic lansoprazole. The plasma concentrations of lansoprazole enantiomers and lansoprazole sulphone were subsequently measured for 24 h post lansoprazole administration using liquid chromatography.

RESULTS

In the homEMs and hetEMs, fluvoxamine significantly increased the AUC(0, infinity) and C(max) and prolonged the elimination half-life of both (R)- and (S)-lansoprazole, whereas in the PMs, the only statistically significant effect of fluvoxamine was on the AUC(0, infinity) for (R)-lansoprazole. The mean fluvoxamine-mediated percent increase in the AUC(0, infinity) of (R)-lansoprazole in the homEMs compared with the PMs was significant (P = 0.0117); however, C(max) did not differ among the three CYP2C19 genotypes. On the other hand, fluvoxamine induced a significant percent increase in both the AUC(0, infinity) and C(max) for (S)-lansoprazole in the homEMs compared with the hetEMs (P = 0.0007 and P = 0.0125, respectively) as well as compared with the PMs (P < 0.0001 for each parameter). The mean R : S ratio for AUC(0, infinity) of lansoprazole in the homEMs was significantly different between the placebo and the fluvoxamine treatment groups (12.7 (9.1, 16.8) vs 6.4 (5.4, 7.4), respectively, P < 0.0001), though not in the PMs (5.5 (4.3, 6.7) vs 5.9 (5.3, 6.5), respectively).

CONCLUSIONS

The magnitude of the contribution of CYP2C19 to the metabolism of (S)-lansoprazole is much greater compared with that of the (R)-enantiomer. In extensive metabolizers, hepatic CYP2C19 plays an important role in the absorption and elimination of lansoprazole, particularly the (S)-enantiomer.

A comparative study on endoscopic ulcer healing of omeprazole versus rabeprazole with respect to CYP2C19 genotypic differences

Omeprazole is mainly metabolized in the liver by CYP2C19, a genetically determined enzyme, while rabeprazole is mainly nonenzymatically degraded with a minor involvement by CYP2C19. We investigated the gastric ulcer healing effect of omeprazole versus rabeprazole evaluated endoscopically with reference to the different CYP2C19 genotypes. Eighty patients with active gastric ulcer were treated with a daily dose of 20 mg of omeprazole or 10 mg of rabeprazole. The endoscopic evaluation was performed at the baseline and 2- and 8-week posttreatment periods. The endoscopic improvement of gastric ulcer size and ulcer healing rates using a thin rubber disc with a diameter of 6 mm, were evaluated in relation to the CYP2C19 genotypic status. The mean 2-week posttreatment ulcer size value by rabeprazole did not significantly differ among the different CYP2C19 genotypes, whereas the mean value in the homozygous extensive metabolizer patients treated with omeprazole was significantly (P = 0.0057) greater than in those with rabeprazole. However, after the 8-week treatment, omeprazole and rabeprazole showed the similarly high healing rates of 87.8% (31/37) and 88.9% (32/36), respectively. Although both omeprazole and rabeprazole showed a high healing rate of gastric ulcer after the 8-week treatment period, the healing effect of rabeprazole appears to be relatively independent of the CYP2C19 status, resulting in an earlier repair of gastric mucosal damage evaluated endoscopically compared to that of omeprazole.

Effects of clarithromycin on lansoprazole pharmacokinetics between CYP2C19 genotypes

AIMS

Lansoprazole is a substrate of CYP2C19 and CYP3A. The aim of this study was to compare the inhibitory effects of clarithromycin, an inhibitor of CYP3A on the metabolism of lansoprazole between CYP2C19 genotypes.

METHODS

A two-way randomized double-blind, placebo-controlled crossover study was performed. Eighteen volunteers, of whom six were homozygous extensive metabolizers (EMs), six were heterozygous EMs and six were poor metabolizers (PMs) for CYP2C19, received two 6-day courses of either clarithromycin 800 mg or placebo daily in a randomized fashion with a single oral dose of lansoprazole 60 mg on day 6 in all cases. Plasma concentrations of lansoprazole and its metabolites, 5-hydroxylansoprazole and lansoprazole sulphone were monitored up to 24 h after dosing.

RESULTS

During placebo administration, the mean AUC0, infinity of lansoprazole in homozygous EMs, heterozygous EMs and PMs were 4652 (95% CI, 2294, 7009) ng ml(-1) h, 8299 (4784, 11814) ng ml(-1) h and 25293 (17643, 32943) ng ml(-1) h (P < 0.001), respectively. Clarithromycin treatment significantly increased Cmax by 1.47-fold, 1.71-fold and 1.52-fold and AUC0, infinity of lansoprazole by 1.55-fold, 1.74-fold, and 1.80-fold in these genotype groups, respectively, whereas elimination half-life was prolonged only in PMs. The clarithromycin-mediated percent increase in pharmacokinetic parameters such as Cmax, AUC0, infinity or elimination half-life did not differ between the three CYP2C19 genotypes.

CONCLUSIONS

The present study indicates that there are significant drug interactions between lansoprazole and clarithromycin in all CYP2C19 genotype groups probably through CYP3A inhibition. The bioavailability of lansoprazole might, to some extent, be increased through inhibition of P-glycoprotein during clarithromycin treatment.

Effect of concomitant dosing of famotidine with lansoprazole on gastric acid secretion in relation to CYP2C19 genotype status

BACKGROUND

Famotidine increases Helicobacter pylori-eradication rates by a triple lansoprazole/amoxicillin/clarithromycin therapy in patients with the rapid extensive metabolizer genotype of CYP2C19.

AIM

To determine the effect of famotidine on the gastric acid inhibition by lansoprazole in relation to CYP2C19 genotypes.

METHODS

Twenty healthy volunteers with different CYP2C19 genotypes--consisting of six rapid extensive metabolizers, nine intermediate metabolizers and five poor metabolizers--underwent three 7-day courses with placebo, lansoprazole 30 mg twice daily, and lansoprazole 30 mg twice plus famotidine 20 mg twice daily. Lansoprazole was dosed after breakfast and dinner. Famotidine was dosed after lunch and at bedtime. Intragastric pH monitoring was performed for 24 h on day 7 of each course.

RESULTS

With placebo, no difference was observed in intragastric pH profiles among the three CYP2C19 genotype groups. With lansoprazole 30 mg twice daily, the median of 24-h intragastric pH in poor metabolizers (6.1) was significantly higher than those of rapid extensive metabolizers (4.5) and intermediate metabolizers (5.0), respectively (P = 0.0176 and 0.0388), whereas with lansoprazole 30 mg twice and famotidine 20 mg twice daily, the medians were 5.4, 5.7, and 6.1, respectively (not significant).

CONCLUSION

Acid inhibition by lansoprazole was influenced by CYP2C19 genotype status. This influence was offset by the concomitant use of famotidine.

From Physical Pharmacy to Clinical Pharmacology

Research works on molecular interactions in solutions were carried out at School of Pharmacy, the University of Wisconsin under the direction of Prof. T. Higuchi and at Faculty of Pharmaceutical Sciences, Kyoto University under the direction of Prof. H. Sezaki. Studies on permeation of drugs through polymer membranes were carried out at Faculty of Pharmacy and Pharmaceutical Sciences, University of Alberta, Edmonton, Canada and at Pharmaceutical Chemistry Research Laboratories at Food and Drug Directorate, Department of Health and Welfare, Canada. Studies on modification of delivery patterns by means of pharmaceutical approaches were carried out at Faculty of Pharmaceutical Sciences, Hokkaido University. Topics related to modification of drug delivery patterns include employment of amorphous forms such as ground mixture with micro-crystalline cellulose and coprecipitate with polyvinylpyrrolidone, use of biodegradable polymers such as polylactic acid and polycarbonates, gel-forming materials such as konjac, agar and hydroxypropylcellulose, and physicochemical systems such as complexation. Works related to drug delivery and disposition of drugs in humans were carried out at Department of Pharmacy, Kumamoto University Hospital. Topics related to drug delivery in humans include injections containing anticancer drugs for intra-arterial administration, lidocaine gels for dermal anesthesia, glucagon solution for nasal administration. Topics related to disposition of drugs in humans include clinical pharmacokinetic studies in infants and elderly and medical uses of adsorbents.

Effects of fluvoxamine on lansoprazole pharmacokinetics in relation to CYP2C19 genotypes

Lansoprazole is a substrate of CYP2C19 and CYP3A4. The aim of this study was to compare the inhibitory effects of fluvoxamine, an inhibitor of CYP2C19, on the metabolism of lansoprazole between CYP2C19 genotypes. Eighteen volunteers--of whom 6 were homozygous extensive metabolizers (EMs), 6 were heterozygous EMs, and 6 were poor metabolizers (PMs) for CYP2C19--received three 6-day courses of either daily 50 mg fluvoxamine or placebo in a randomized fashion with a single oral 60-mg dose of lansoprazole on day 6 in all cases. Plasma concentrations of lansoprazole and its metabolites, 5-hydroxylansoprazole and lansoprazole sulfone, were monitored up to 24 hours after the dosing. During placebo administration, there was a significant difference in the area under the plasma concentration-time curve from time 0 to infinity (AUC(0-infinity)) of lansoprazole between CYP2C19 genotypes. Fluvoxamine treatment increased AUC(0-infinity) of lansoprazole by 3.8-fold (P < .01) in homozygous EMs and by 2.5-fold (P < .05) in heterozygous EMs, whereas no difference in any pharmacokinetic parameters was found in PMs. There was a significant difference in the fluvoxamine-mediated percentage increase in the AUC(0-infinity) of lansoprazole between CYP2C19 genotypes. The present study indicates that there are significant drug interactions between lansoprazole and fluvoxamine in EMs. CYP2C19 is predominantly involved in lansoprazole metabolism in EMs.

Determination of lansoprazole and two of its metabolites by liquid–liquid extraction and automated column-switching high-performance liquid chromatography: application to measuring CYP2C19 activity

A simple and sensitive column-switching high-performance liquid chromatographic (HPLC) method for the simultaneous determination of lansoprazole, a proton pump inhibitor and its major metabolites: 5-hydroxylansoprazole and lansoprazole sulfone in human plasma. The test compounds were extracted from 1 mL of plasma using diethyl ether-dichloromethane (7:3, v/v) mixture and the extract was injected into a column I (TSK-PW precolumn, 10 microm, 3.5 mm x 4.6 mm i.d.) for clean-up and column I (C(18) STR ODS-II analytical column, 5 microm, 150 mm x 4.6 mm i.d.) for separation. The peak was detected by a ultraviolet detector set at a wavelength of 285 nm, and the total time for a chromatographic separation was approximately 25 min. The method was validated for the concentration range from 3 to 5000 ng/mL. Mean recoveries were 74.0% for lansoprazole, 68.3% for 5-hydroxylansoprazole, and 79.4% for lansoprazole sulfone. Intra- and inter-day relative standard derivatives were less than 6.1 and 5.1% for lansoprazole, 5.8 and 5.8% for 5-hydroxylansoprazole, 4.4 and 5.9% for lansoprazole sulfone, respectively, at the different concentration ranges. This method is suitable for use in therapeutic drug monitoring and pharmacokinetic studies, and provides use tool for measuring CYP2C19 activity.

Effect of clarithromycin on the enantioselective disposition of lansoprazole in relation to CYP2C19 genotypes

The aim of this study was to examine the effect of clarithromycin, a CYP3A4 inhibitor, on the enantioselective disposition of lansoprazole among three different CYP2C19 genotype groups in healthy Japanese subjects. These subjects included 6 each of homozygous extensive metabolizers (homEMs), heterozygous extensive metabolizers (hetEMs), and poor metabolizers (PMs). In the EMs of CYP2C19, clarithromycin markedly increased Cmax and the AUC0-infinity of (S)-lansoprazole and (S)-hydroxylansoprazole compared with those of the corresponding (R)-enantiomers. Clarithromycin significantly increased Cmax and the AUC0-infinity of (S)-lansoprazole in the homEMs by 110% and 115%, respectively, and in the hetEMs by 105% and 103%, respectively, compared with placebo. Furthermore, clarithromycin slightly prolonged the elimination half-life of (R)-lansoprazole in the homEMs and hetEMs but did not alter that of (S)-lansoprazole. In the of PMs CYP2C19, clarithromycin significantly increased Cmax and the AUC0-infinity and significantly prolonged the elimination half-lives of (R)- and (S)-lansoprazole by 51% and 49%, respectively. The present study suggests that there are significant drug interactions between (R)- or (S)-lansoprazole and clarithromycin in EMs by inhibiting the CYP3A4-catalyzed sulfoxidation primarily during the first pass, whereas in PMs, the overall metabolism of lansoprazole is inhibited.

Effect of lansoprazole and rabeprazole on tacrolimus pharmacokinetics in healthy volunteers with CYP2C19 mutations

The aim of this study was to investigate the effects of the proton pump inhibitors (PPIs), lansoprazole and rabeprazole, on tacrolimus pharmacokinetics in healthy volunteers with mutations in the cytochrome P450 (CYP) 2C19 gene (CYP2C19). An open-label crossover study was performed with 19 healthy subjects. Tacrolimus (2 mg) was administered orally with and without lansoprazole (30 mg per day for 4 days) or rabeprazole (10 mg per day for 4 days). Blood concentrations of tacrolimus were determined before and 1, 2, 4 and 8 h after dosing. Genotyping for CYP2C19 was conducted by a polymerase chain reaction-restriction fragment length polymorphism method. Coadministration of lansoprazole significantly decreased the oral tacrolimus clearance, resulting in an increase in the area under the blood concentration-time curve (AUC0-8) (control vs with lansoprazole: 29.7 +/- 3.5 vs 44.1 +/- 5.0 ng h mL(-1), P < 0.05). Large individual variation was observed in the effects of lansoprazole on tacrolimus AUC0-8 owing to CYP2C19 genotype status. The percent change for tacrolimus AUC0-8 in subjects with and without CYP2C19 mutant alleles was 81% and 29%, respectively. Coadministration of rabeprazole also increased the mean AUC0-8 of tacrolimus, but the difference was not statistically significant. These observations suggest that drug interaction between tacrolimus and lansoprazole occurs in subjects with higher lansoprazole blood concentrations corresponding to CYP2C19 genetic status. In contrast, rabeprazole has minimal effect on tacrolimus pharmacokinetics regardless of CYP2C19 genotype status.

Pharmacokinetic differences between the enantiomers of lansoprazole and its metabolite, 5-hydroxylansoprazole, in relation to CYP2C19 genotypes

OBJECTIVE

The purpose of this study was to elucidate the pharmacokinetics of each enantiomer of lansoprazole and 5-hydroxylansoprazole in three different CYP2C19 genotype groups of Japanese subjects.

METHODS

Healthy subjects ( n=18), of whom 6 were homozygous extensive metabolizers (homEMs), 6 were heterozygous extensive metabolizers (hetEMs) and 6 were poor metabolizers (PMs), participated in the study. After a single oral dose of 60 mg of racemic lansoprazole, the plasma concentrations of the lansoprazole enantiomers, 5-hydroxylansoprazole enantiomers and lansoprazole sulfone were measured for 24 h post-dose.

RESULTS

The plasma concentrations of ( R)-lansoprazole were remarkably higher in all three CYP2C19 genotype groups than those of the corresponding ( S)-enantiomer. The mean maximum plasma concentration ( C(max)) of ( S)-lansoprazole differed significantly among the three groups, whereas there was no difference for the ( R)-enantiomer. The relative area under the plasma concentration (AUC) ratios of ( R)- and ( S)-lansoprazole in the homEMs, hetEMs, and PMs were 1:1.5:4.0 and 1:1.8:7.4, respectively. Yet, the relative AUC ratios of 5-hydroxylansoprazole to lansoprazole for the ( R)- and ( S)-enantiomers in the homEMs, hetEMs, and PMs were almost the same (1:0.73:0.12 and 1:0.77:0.13, respectively). However, the AUC ratios of the ( S)-enantiomer were 13-fold greater for the three CYP2C19 genotypes than those of the corresponding ( R)-enantiomer.

CONCLUSIONS

The magnitude of the contribution of CYP2C19 to the 5-hydroxylation of ( S)-lansoprazole was greater than that of the ( R)-enantiomer. The R/S ratios for the AUC of lansoprazole for the homEMs, hetEMs and PMs were 12.7, 8.5 and 5.8, respectively, suggesting a significant effect of CYP2C19 polymorphisms on the stereoselective disposition of lansoprazole.

Lansoprazole—Tacrolimus Interaction in Japanese Transplant Recipient with CYP2C19 Polymorphism

OBJECTIVE

To report a patient with a high tacrolimus blood concentration after lansoprazole administration and assess the potential interaction between tacrolimus and lansoprazole.

CASE SUMMARY

A 34-year-old Japanese man underwent a living-donor kidney transplantation having received tacrolimus, mycophenolate mofetil, and prednisolone for immunosuppression. Lansoprazole was administered from postoperative day 4 as prophylaxis of ulcers. The trough concentration of tacrolimus increased markedly after the introduction of lansoprazole, while results of liver function tests were within normal limits. Lansoprazole was stopped on day 15 and was replaced with famotidine on day 17. The trough concentration of tacrolimus returned to the therapeutic range after administration of lansoprazole ceased. Genetic analysis revealed a heterozygous mutation at exon 5 of the CYP2C19 gene (CYP2C19*1/*2) in this patient.

DISCUSSION

Lansoprazole is metabolized by 2 enzymes, CYP2C19 and CYP3A4. Since tacrolimus is also metabolized by CYP3A4, the blood concentration of tacrolimus in this patient who had a CYP2C19 gene mutation may have been elevated by decreased hepatic elimination of lansoprazole. An objective causality assessment revealed that this interaction was probable.

CONCLUSIONS

Trough concentrations of tacrolimus should be monitored closely for optimizing the dosage regimen in patients receiving concomitant lansoprazole.

The effects of lansoprazole on erosive reflux oesophagitis are influenced by CYP2C19 polymorphism

BACKGROUND

The acid suppressive effect of lansoprazole is influenced by the P450 2C19 (CYP2C19) polymorphism.

AIM

To investigate whether the CYP2C19 genotype is related to the healing of erosive reflux oesophagitis during treatment with lansoprazole.

METHODS

Eighty-eight Japanese patients with erosive reflux oesophagitis were treated with a daily oral dose of 30 mg lansoprazole for 8 weeks. The CYP2C19 genotype, Helicobacter pylori infection status and serum pepsinogen I/II ratio were assessed before treatment. At 4 and 8 weeks, the healing of erosive reflux oesophagitis was evaluated endoscopically.

RESULTS

The healing rates were 57.1%, 69.2% and 72.7% at 4 weeks and 77.4%, 95.0% and 100% at 8 weeks in homozygous extensive metabolizers, heterozygous extensive metabolizers and poor metabolizers, respectively. At 8 weeks, the healing rate of erosive reflux oesophagitis was significantly lower in homozygous extensive metabolizers than in the other two groups (P < 0.05). The H. pylori status and serum pepsinogen I/II ratio had less influence than CYP2C19 polymorphism on the healing rate of erosive reflux oesophagitis.

CONCLUSIONS

The therapeutic effect of lansoprazole on erosive reflux oesophagitis is influenced by the CYP2C19 genotype status. Therefore, a test of CYP2C19 genotype may be useful for the medical treatment of reflux oesophagitis with lansoprazole.

Bioinformatics Research on Inter-racial Difference in Drug Metabolism II. Analysis on Relationship between Enzyme Activities of CYP2D6 and CYP2C19 and their Relevant Genotypes

The enzyme activities of CYP2D6 and CYP2C19 show a genetic polymorphism, and the frequency of poor metabolizers (PMs) on these enzymes depends on races. We have analyzed frequencies of mutant alleles and PMs based on the published data in previous study (Shimizu, T. et al.: Bioinformatics research on inter-racial difference in drug metabolism, I. Analysis on frequencies of mutant alleles and poor metabolizers on CYP2D6 and CYP2C19.). The study shows that there were racial differences in the frequencies of each mutant allele and PMs. In the present study, the correlation between genotypes and drug-metabolizing enzyme activities was investigated. The result showed that enzyme activities varied according to the genotypes of subjects even in the same race. On the other hand, if subjects had the same genotypes, almost no racial differences were observed in drug-metabolizing enzyme activities. From these results, it was supposed that the racial differences in activities of these enzymes could be explained by the differences in distribution of genotypes. It would be possible to explain the racial differences in drug-metabolizing enzyme activities based on the differences on individual pharmacogenetic background information, not merely by comparison of frameworks such as races and nations.

Proton pump inhibitors--differences emerge in hepatic metabolism

Differences are emerging with respect to the mode of metabolism of proton pump inhibitors. All, except rabeprazole, are metabolised primarily by the hepatic cytochrome P450 enzyme system, and common genetic polymorphisms of the CYP 2C19 iso-enzyme affect their clearance and bio-availability. This has been demonstrated to lead to inconsistency in terms of acid suppression across the CYP 2C19 genotypes for all proton pump inhibitors except for rabeprazole. Omeprazole and, more markedly, esomeprazole, differ from the other proton pump inhibitors in that their bio-availability increases over the first week of treatment. This is due to a progressive reduction in their hepatic clearance with repeat dosing. This reduced hepatic clearance appears to be due to the S-enantiomer of omeprazole-esomeprazole impairing the activity of hepatic CYP 2C19. The clinical significance of these differences in metabolism of the various proton pump inhibitors, and the possible benefits of the non-enzymatic metabolism of rabeprazole, require further investigation.

Comparison of lansoprazole and famotidine for gastric acid inhibition during the daytime and night-time in different CYP2C19 genotype groups

BACKGROUND

The acid inhibitory effect of lansoprazole depends on the S-mephenytoin 4'-hydroxylase (CYP2C19) genotype status. The effect of famotidine is independent of this genotype.

AIM

To investigate the acid inhibitory effects of lansoprazole vs. famotidine during the daytime and night-time with reference to different CYP2C19 genotypes.

METHODS

Fifteen healthy volunteers were given 20 mg famotidine twice a day or 30 mg lansoprazole once a day for 8 days. On post-dose day 8, 24-h intragastric pH monitoring was performed.

RESULTS

During the daytime, the intragastric pH with lansoprazole was significantly higher than that with famotidine in the heterozygous extensive metabolizer group, whereas no significant difference was observed in the homozygous extensive metabolizer group. During the night-time, the intragastric pH with famotidine was quite similar to that with lansoprazole in the heterozygous extensive metabolizer and poor metabolizer groups. However, during the night-time, the intragastric pH with famotidine was significantly higher than that with lansoprazole in the homozygous extensive metabolizer group.

CONCLUSIONS

An insufficient acid inhibition by lansoprazole during the night-time in the homozygous extensive metabolizer group could be compensated for by famotidine. CYP2C19 genotype testing appears to be useful for predicting the optimal acid inhibitory drug treatment collated with circadian intragastric pH change.

Identification of N-acetyltransferase 2 and CYP2C19 genotypes for hair, buccal cell swabs, or fingernails compared with blood

Genotyping of polymorphic drug metabolizing enzymes may be useful to estimate the blood concentration, efficacy, and toxicity of drugs before administration. Blood samples are most generally used for genotyping; however, sampling is invasive and complicated by handling and transport. Therefore, the authors developed genotyping methods using nonblood specimens, and then each genotype was compared with that from blood. Healthy Japanese volunteers provided hairs (n = 50), buccal cell swabs (n = 50), and fingernails (n = 30) for N-acetyltransferase 2 and CYP2C19 genotyping. Recovery of genomic DNA from each nonblood specimen was lower than that from 0.5 mL blood. Using a modification of the DNA extraction and polymerase chain reaction amplification method, genotypes were diagnosed without failure, even for those with very low levels of DNA. Both genotypes from these specimens completely matched the genotypes from the blood of the same subject. These nonblood specimens can be convenient, accessible, and economical alternatives to blood as a source of DNA for genotyping.