Role of CYP3A4 and CYP2C19 in the stereoselective metabolism of lansoprazole by human liver microsomes

Lansoprazole Ameliorates Isoniazid-Induced Liver Injury

Isoniazid is a first-line drug in antitubercular therapy. Isoniazid is one of the most commonly used drugs that can cause liver injury or acute liver failure, leading to death or emergency liver transplantation. Therapeutic approaches for the prevention of isoniazid-induced liver injury are yet to be established. In this study, we identified the gene expression signature for isoniazid-induced liver injury using a public transcriptome dataset, focusing on the differences in susceptibility to isoniazid in various mouse strains. We predicted that lansoprazole is a potentially protective drug against isoniazid-induced liver injury using connectivity mapping and an adverse event reporting system. We confirmed the protective effects of lansoprazole against isoniazid-induced liver injury using zebrafish and patients' electronic health records. These results suggest that lansoprazole can ameliorate isoniazid-induced liver injury. The integrative approach used in this study may be applied to identify novel functions of clinical drugs, leading to drug repositioning.

Chiral Switch: Between Therapeutical Benefit and Marketing Strategy

Chirality of pharmaceutical substances is an important aspect in drug research because it determines how enantiomers will interact with chiral biological targets. Enantiomers of a chiral drug can have different pharmacokinetic and pharmacological profiles; consequently, using a single pure enantiomer instead of a racemate can enhance the effectiveness and/or safety of the treatment. The tendencies of modern pharmaceutical industry regarding the current market of chiral drugs are divided between the chiral switch of previously used racemates and the development of new enantiopure drugs. The term chiral switch refers to the replacement on the market of a previously approved racemate with its single enantiomer version. The potential advantages of chiral switch can be related to a higher therapeutic index due to better potency, selectivity and fewer adverse effects, faster onset of action and exposure of the patient to lower drug dosages. However, chiral switch is also a strategy that permits manufacturers to keep market exclusivity for chiral pharmaceuticals that have lost their patent protection, even if the pure enantiomers have not demonstrated higher effectiveness or safety profile compared with the racemates.

Chiral separation in the class of proton pump inhibitors by chromatographic and electromigration techniques: An overview

Proton pump inhibitors (PPIs) are benzimidazole-derivative chiral sulfoxides, frequently used in the treatment of gastric hyperacidity-related disorders. Due to their stereoselective metabolism, the eutomeric forms of PPIs can present a more advantageous pharmacokinetic profile by comparison with the distomers or racemates. Moreover, two representatives of the class are used in therapy both as racemates and as pure enantiomers (esomeprazole, dexlansoprazole). A relatively large number of enantioseparation methods employed for the stereoselective determination of PPIs from pharmaceutical, biological, and environmental matrices were published in the past three decades. The purpose of the current overview is to provide a systematic survey of the available chiral separation methods published since the introduction of PPIs in the therapy up to the present. Analytical and bioanalytical methods using different chromatographic and electromigration techniques reported for the enantioseparation of omeprazole, lansoprazole, pantoprazole, rabeprazole, ilaprazole, and tenatoprazole are included. The analytical conditions of the presented methods are summarized in three comprehensive tables, while a critical discussion of the applied techniques, possible mechanism of enantiorecognition, and future perspectives on the topic are also presented.

Investigating the clinical factors and comedications associated with circulating levels of atorvastatin and its major metabolites in secondary prevention

Aims The lipid-lowering drug, atorvastatin (ATV), is 1 of the most commonly prescribed medications worldwide. The aim of this study was to comprehensively investigate and characterise the clinical factors and comedications associated with circulating levels of ATV and its metabolites in secondary prevention clinical practice. Methods The plasma concentrations of ATV, 2-hydroxy (2-OH) ATV, ATV lactone (ATV L) and 2-OH ATV L were determined in patients 1 month after hospitalisation for a non-ST elevation acute coronary syndrome. Factors were identified using all subsets multivariable regression and model averaging with the Bayesian information criterion. Exploratory genotype-stratified analyses were conducted using ABCG2 rs2231142 (Q141K) and CYP2C19 metaboliser status to further investigate novel associations. Results A total of 571 patients were included; 534 and 37 were taking ATV 80 mg and 40 mg daily, respectively. Clinical factors associated with ATV and/or its metabolite levels included age, sex, body mass index and CYP3A inhibiting comedications. Smoking was newly associated with increased ATV lactonisation and reduced hydroxylation. Proton pump inhibitors (PPIs) and loop diuretics were newly associated with modestly increased levels of ATV (14% and 38%, respectively) and its metabolites. An interaction between PPIs and CYP2C19 metaboliser status on exposure to specific ATV analytes (e.g. interaction P = .0071 for 2-OH ATV L) was observed. Overall model R² values were 0.14-0.24.ConclusionMultiple factors were associated with circulating ATV and metabolite levels, including novel associations with smoking and drug-drug(-gene) interactions involving PPIs and loop diuretics. Further investigations are needed to identify additional factors that influence ATV exposure.

Dexlansoprazole: delayed-release orally disintegrating tablets for the treatment of heartburn associated with non-erosive gastroesophageal reflux disease and the maintenance of erosive esophagitis

Gastroesophageal reflux disease (GERD) is a common condition afflicting millions of patients, whose prevalence continues to rise owing to the aging population and increasing burden of comorbid conditions, such as obesity. Currently, the mainstay of therapy for GERD is treatment with proton pump inhibitors (PPIs), which have proven efficacy, safety, and tolerability. Despite this, a considerable number of patients have refractory symptoms to PPI therapy. Dexlansoprazole is a new addition to the class of PPIs, which has a unique dual delayed drug release system, which aims to address the current limitations of acid suppressive therapy by offering extended acid suppression and improved ease of administration. Areas covered: This manuscript covers the pharmacokinetics, pharmacodynamics, clinical efficacy, and regulatory approval of dexlansoprazole. Additionally, there is further discussion concerning the current market settings and the potential future impact of dexlansoprazole. Expert commentary: Overall, dexlansoprazole offers benefits in its ease of administration and proven efficacy in the healing, maintenance of erosive esophagitis, and symptomatic non-erosive GERD. Long-term, dexlansoprazole will likely find a niche market among patients who fail other acid suppressive therapy or who desire simplified administration for compliance concerns, but will likely come at a higher out of pocket expense than comparable generic PPIs.

Role of Stereoselective Assays in Bioequivalence Studies of Racemic Drugs: Have We Reached a Consensus?

The existence of stereoselectivity in metabolism and drug disposition, coupled with the existence of genetic polymorphisms and modulation of enantiomeric kinetics via special delivery systems, provides some compulsion to assess bioequivalence using stereoselective data. However, examination of the literature suggests that nonstereoselective data are commonly used for the bioequivalence assessment of drug racemates.

Ilaprazole, a new proton pump inhibitor, is primarily metabolized to ilaprazole sulfone by CYP3A4 and 3A5

Ilaprazole is a new proton pump inhibitor, designed for treatment of gastric ulcers, and developed by Il-Yang Pharmaceutical Co (Seoul, Korea). It is extensively metabolised to the major metabolite ilaprazole sulfone. In the present study, several in vitro approaches were used to identify the cytochrome P450 (CYP) enzymes responsible for ilaprazole sulfone formation. Concentrations of ilaprazole sulfone were determined by liquid chromatography-tandem mass spectrometry (LC-MS/MS). Incubation of ilaprazole with cDNA-expressed recombinant CYPs indicated that CYP3A was the major enzyme that catalyses ilaprozole to ilaprazole sulfone. This reaction was inhibited significantly by ketoconazole, a CYP3A inhibitor, and azamulin, a mechanism-based inhibitor of CYP3A, while no substantial effect was observed using selective inhibitors for eight other P450s (CYP1A2, CYP2A6, CYP2B6, CYP2C8, CYP2C9, CYP2C19, CYP2D6, and CYP2E1). In addition, the formation of ilaprazole sulfone correlated well with CYP3A-catalysed testosterone 6β-hydroxylation and midazolam 1'-hydroxylation in 20 different human liver microsome panels. The intrinsic clearance of the formation of ilaprazole sulfone by CYP3A4 was 16-fold higher than that by CYP3A5. Collectively, these results indicate that the formation of the major metabolite of ilaprazole, ilaprazole sulfone, is predominantly catalysed by CYP3A4/5.

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.

Do proton pump inhibitors attenuate the effect of aspirin on platelet aggregation? A randomized crossover study

It is common practice to coadminister proton pump inhibitors with aspirin to diminish the risk of upper gastrointestinal bleeding. This is the first study that investigated the potential impact of a proton pump inhibitor on aspirin effects on platelet aggregation. Twenty-four hypertensive subjects eligible for treatment with low-dose enteric-coated aspirin (LDECA) for primary prevention of cardiovascular disease were randomized to receive 100 mg LDECA or 100 mg LDECA plus 30 mg lansoprazole for 4 weeks. Then, participants were crossed over to the alternative regimen for another 4 weeks. Salicylic, gastrin, and pepsinogen I blood level counting were used to ensure adherence to treatment. Platelet aggregation was evaluated by light transmittance aggregometry and PFA100. The LDECA administration reduced arachidonic acid (P < 0.001), collagen (P < 0.01), and epinephrine (P < 0.001) tests. These changes paralleled an increase in collagen/epinephrine duration (P < 0.001) but not in collagen/adenosine diphosphate duration and platelet count. No significant difference was found in any of these platelets' function tests with LDECA alone versus LDECA plus lansoprazole. A significant increase in salicylic levels was observed in patients on LDECA as well as in those on LDECA plus lansoprazole, whereas gastrin and pepsinogen I levels were increased only when lansoprazole was added. These data suggest that the concomitant use of the lansoprazole at 30-mg daily does not influence the long-term effect of LDECA on platelet aggregation. Furthermore, they might imply that an interaction of LDECA with other proton pump inhibitors on platelet aggregation is unlikely.

Delayed release dexlansoprazole in the treatment of GERD and erosive esophagitis

Although proton pump inhibitors (PPI) have a record of remarkable effectiveness and safety in the management of gastroesophageal reflux disease (GERD), several treatment challenges with PPI have emerged. Dexlansoprazole MR is the (R)-enantiomer of lansoprazole contained in a formulation that produces two distinct releases of drug and significantly extends the duration of active plasma concentrations and % time pH > 4 beyond that of conventional single-release PPI. Dexlansoprazole MR can be administered without regard to meals or the timing of meals in most patients. Dexlansoprazole MR 60 mg demonstrated similar efficacy for healing of erosive esophagitis at 8 weeks compared with lansoprazole 30 mg, and dexlansoprazole MR 30 mg was superior to placebo for maintenance of healed erosive esophagitis at 6 months with 99% of nights and 96% of days heartburn-free over 6 months in patients taking dexlansoprazole MR 30 mg. Superior relief of heartburn occurred in patients taking dexlansoprazole MR 30 mg (55% heartburn-free 24-hour periods) vs placebo (14%) for symptomatic nonerosive GERD. The safety profile of dexlansoprazole MR is similar to that of lansoprazole. The extended pharmacodynamic effects, added convenience, and efficacy and safety of dexlansoprazole MR offer a novel approach to gastric pH control in patients with acid-related disorders.

Polymorphism of human cytochrome P450 enzymes and its clinical impact

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

Age-dependent pharmacokinetics of lansoprazole in neonates and infants

BACKGROUND

Evidence suggests that age may affect the pharmacokinetics of lansoprazole in pediatric patients, but little information is available in neonates and infants.

OBJECTIVE

To determine the pharmacokinetics of lansoprazole in neonates and infants <1 year of age with gastroesophageal reflux disease (GERD)-associated symptoms.

METHODS

Two single- and repeated-dose, randomized, open-label, multicenter studies were conducted. Studies involved a pretreatment period of 7 or 14 days, a dose administration period of 5 days, and a follow-up period of 30 days for adverse events collection. The studies were conducted in both hospital and private clinic settings. The studies were performed in 24 neonates (aged <or=28 days) and 24 infants (aged >28 days, but <1 year) with GERD-associated symptoms diagnosed by medical history and the clinical judgment of the treating physician. Participants received lansoprazole 0.5 or 1.0 mg/kg/day (neonates) or 1.0 or 2.0 mg/kg/day (infants) for 5 days. Plasma pharmacokinetic parameters on dose administration day 1 were calculated, and plasma concentrations on day 5 were obtained.

RESULTS

The pharmacokinetics of lansoprazole were approximately dose proportional. After a single dose in neonates, the mean maximum plasma concentrations (C(max)) were 831 and 1672 ng/mL, and the mean area under the plasma concentration-time curve (AUC) values were 5086 and 9372 ng . h/mL for lansoprazole doses of 0.5 and 1.0 mg/kg, respectively. The time to C(max) (t(max)) [3.1 hours] and harmonic mean terminal elimination half-life (t((1/2))) [2.8 hours] were slightly longer in neonates receiving 0.5 mg/kg than the t(max) (2.6 hours) and t((1/2)) (2.0 hours) values observed in neonates receiving 1.0 mg/kg. Mean oral clearance (CL/F) was identical for the two doses (0.16 L/h/kg). After a single 1.0 or 2.0 mg/kg dose in infants, the lansoprazole C(max) values were 959 and 2087 ng/mL and the mean AUC values were approximately 2203 and 5794 ng . h/mL, respectively. The mean t(max) and mean t((1/2)) were 1.8 hours and 0.8 hours, respectively, for both doses (1.0 or 2.0 mg/kg), while mean CL/F was 0.71 and 0.61 L/h/kg, respectively. In both patient groups, mean plasma concentrations on day 5 were similar to day 1 concentrations. No clinically meaningful accumulation was observed following 5 days' dose administration. Plots of lansoprazole pharmacokinetics against chronologic age showed that dose-normalized C(max), t((1/2)), and AUC were two, three, and five times higher, respectively, in study participants aged <or=10 weeks than in study participants aged >10 weeks-1 year. Lansoprazole was well tolerated in all patients.

CONCLUSIONS

The pharmacokinetics of lansoprazole in pediatric patients are age dependent, with those aged <or=10 weeks showing higher plasma exposure and lower plasma clearance than those aged >10 weeks-1 year. Thus, pediatric patients aged <or=10 weeks require a lower dose of lansoprazole than pediatric patients aged >10 weeks to achieve similar plasma exposure.

Stereoselective disposition of proton pump inhibitors

It is estimated that about half of all therapeutic agents are chiral, but most of these drugs are administered in the form of the racemic mixture, i.e. a 50/50 mixture of its enantiomers. However, chirality is one of the main features of biology, and many of the processes essential for life are stereoselective, implying that two enantiomers may work differently from each other in a physiological environment. Thus, receptors or metabolizing enzymes would recognize one of the ligand enantiomers in favour of the other. With one exception, all presently marketed proton pump inhibitors (PPIs)--omeprazole, lansoprazole, pantoprazole and rabeprazole--used for the treatment of gastric acid-related diseases are racemic mixtures. The exception is esomeprazole, the S-enantiomer of omeprazole, which is the only PPI developed as a single enantiomer drug. The development of esomeprazole (an alkaline salt thereof, e.g. magnesium or sodium) was based on unique metabolic properties that clearly differentiated esomeprazole from omeprazole, the racemate. At comparable doses, these properties led to several clinical advantages, for example higher bioavailability in the majority of patients, i.e. the extensive metabolizers (EMs; 97% in Caucasian and 80-85% in Asian populations), lower exposure in poor metabolizers (PMs; 3% in Caucasian and 15-20% in Asian populations) and lower interindividual variation. For the other, i.e. racemic, PPIs there are some data available on the characteristics of the individual enantiomers, and we have therefore undertaken to analyse the current literature with the purpose of evaluating the potential benefits of developing single enantiomer drugs from lansoprazole, pantoprazole and rabeprazole. For lansoprazole, the plasma concentrations of the S-enantiomer are lower than those of the R-enantiomer in both EMs and PMs, and, consequently, the variability in the population or between EMs and PMs is not likely to decrease with either of the lansoprazole enantiomers. Furthermore, plasma protein binding differs between the two lansoprazole enantiomers, in that the amount of the free S-enantiomer is two-fold higher than that of the R-enantiomer. This will counteract the difference seen in total plasma concentrations of the enantiomers. Also, studies using expressed human cytochrome P450 isoenzymes show that the metabolism of one enantiomer is significantly affected by the presence of the other, which is likely to result in different pharmacokinetics when administering a single enantiomer. For pantoprazole, there is a negligible difference in plasma concentrations between the two enantiomers in EMs, while the difference is substantial in PMs. The difference in AUC between PMs and EMs would decrease to some extent, but in the majority of the population the variability and efficacy would not be altered with a single enantiomer of pantoprazole. The metabolism of the enantiomers of rabeprazole displays stereoselectivity comparable to that of lansoprazole, i.e. the exposure of the R-enantiomer is higher than that of the S-enantiomer in EMs as well as in PMs, which, by analogy to lansoprazole, makes them less suitable for development of a single enantiomer drug. Furthermore, the chiral stability of the rabeprazole enantiomers may be an issue because of significant degradation of rabeprazole to its sulfide analogue, which is subject to non-stereoselective metabolic regeneration of a mixture of the two enantiomers. In conclusion, in contrast to esomeprazole, the S-enantiomer of omeprazole, minimal if any clinical advantages would be expected in developing any of the enantiomers of lansoprazole, pantoprazole, or rabeprazole as compared with their racemates.

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.

Stereoselective inhibition of cytochrome P450 forms by lansoprazole and omeprazolein vitro

The stereoselectivity of the inhibitory interaction potential of lansoprazole and omeprazole isomers on six human cytochrome P450 forms was evaluated using human liver microsomes. Lansoprazole enantiomers showed stereoselective inhibition of CYP2C9-catalysed tolbutamide 4-methylhydroxylation, CYP2C19-catalysed S-mephenytoin 4'-hydroxylation, CYP2D6-catalysed dextromethorphan O-demethylation, CYP2E1-catalysed chlorzoxazone 6-hydroxylation and CYP3A4-catalysed midazolam 1-hydroxylation, whereas omeprazole only inhibited CYP2C19 stereoselectively. Of the P450 forms tested, CYP2C19-catalysed S-mephenytoin 4'-hydroxylation was extensively inhibited by both the lansoprazole and omeprazole enantiomers in a competitive and stereoselective manner; the S-enantiomers of both drugs inhibited the hydroxylation more than the R-enantiomers. The estimated K(i) values determined for CYP2C19-catalysed S-mephenytoin 4'-hydroxylation were 0.6, 6.1, 3.4 and 5.7 microM for S-lansoprazole, R-lansoprazole, S-omeprazole and R-omeprazole, respectively. The results indicate that although both lansoprazole and omeprazole are strong inhibitors of CYP2C19, the inhibition of CYP2C19 by lansoprazole is highly stereoselective, whereas the inhibition by omeprazole is less stereoselective. In addition, S-lansoprazole, the most potent CYP2C19 inhibitor, is not a good CYP2C19-selective inhibitor owing to its inhibition of other P450 forms.

Functional pharmacogenetics/genomics of human cytochromes P450 involved in drug biotransformation

We investigated the elimination routes for the 200 drugs that are sold most often by prescription count in the United States. The majority (78%) of the hepatically cleared drugs were found to be subject to oxidative metabolism via cytochromes P450 of the families 1, 2 and 3, with major contributions from CYP3A4/5 (37% of drugs) followed by CYP2C9 (17%), CYP2D6 (15%), CYP2C19 (10%), CYP1A2 (9%), CYP2C8 (6%), and CYP2B6 (4%). Clinically well-established polymorphic CYPs (i.e., CYP2C9, CYP2C19, and CYP2D6) were involved in the metabolism of approximately half of those drugs, including (in particular) NSAIDs metabolized mainly by CYP2C9, proton-pump inhibitors metabolized by CYP2C19, and beta blockers and several antipsychotics and antidepressants metabolized by CYP2D6. In this review, we provide an up-to-date summary of the functional polymorphisms and aspects of the functional genomics of the major human drug-metabolizing cytochrome P450s, as well as their clinical significance.

Pharmacokinetics of the new proton pump inhibitor ilaprazole in Chinese healthy subjects in relation to CYP3A5 and CYP2C19 genotypes

BACKGROUND

PPIs are widely used in peptic diseases, and this paper is to investigate the kinetic characteristics of a new PPI ilaprazole in Chinese healthy subjects and the association with CYP3A5 and CYP2C19 polymorphisms.

METHODS

21 subjects were selected and treated with 10mg ilaprazole according to their CYP3A5*3 genotypes (including 7 of CYP3A5*1/*1, 7 of *1/*3, and 7 of *3/*3). The plasma concentrations of ilaprazole and its metabolites were monitored by LC-MS/MS method.

RESULTS

The C(max), AUC((0-6)), AUC((0-48)) and AUC((0-infinity)) of ilaprazole were all significantly different across the 3 CYP3A5 genotypes (including 4 of CYP3A5*1/*1, 4 of *1/*3, 3 of *3/*3; P<0.05) in CYP2C19 wild-type subjects (CYP2C19 wt/wts), similar variety of C(max) and AUC((0-6)) among CYP3A5 genotypes (including 3 of CYP3A5*1/*1, 3 of *1/*3, 4 of *3/*3; P<0.05) were also observed in CYP2C19 heterozygous subjects (CYP2C19 wt/mts). The sulfoxidation metabolic index (measure of collective CYP3A activity) indicates that the CYP3A5*1/*1, (high-expressers), *1/*3, (low-expressers), and *3/*3 (no-expressers) groups have medium, lowest and highest activities on ilaprazole metabolism, inconsistent with genotype-based CYP3A5 enzymatic activity. Further analysis showed no correlation between ilaprazole metabolism and CYP2C19 genotypes, evidenced by that the AUC((0-infinity)) of ilaprazole from either CYP3A5*1/*1 or CYP3A5*1/*3 groups was much higher in CYP2C19 wt/wts (n=4) than that in CYP2C19 wt/mts (n=3) (P<0.001), but the C(max) and AUC((0-6)) of ilaprazole from CYP3A5*3/*3 groups, were significantly lower in CYP2C19 wt/wts (n=3) compared to CYP2C19 wt/mts (n=4) (P<0.01).

CONCLUSIONS

There was no demonstrated relationship between ilaprazole metabolism and CYP3A5 polymorphisms.

Drug disposition in three dimensions: an update on stereoselectivity in pharmacokinetics

Many marketed drugs are chiral and are administered as the racemate, a 50:50 combination of two enantiomers. Pharmacodynamic and pharmacokinetic differences between enantiomers are well documented. Because of enantioselectivity in pharmacokinetics, results of in vitro pharmacodynamic studies involving enantiomers may differ from those in vivo where pharmacokinetic processes will proceed. With respect to pharmacokinetics, disparate plasma concentration vs time curves of enantiomers may result from the pharmacokinetic processes proceeding at different rates for the two enantiomers. At their foundation, pharmacokinetic processes may be enantioselective at the levels of drug absorption, distribution, metabolism and excretion. In some circumstances, one enantiomer can be chemically or biochemically inverted to its antipode in a unidirectional or bidirectional manner. Genetic consideration such as polymorphic drug metabolism and gender, and patient factors such as age, disease state and concomitant drug intake can all play a role in determining the relative plasma concentrations of the enantiomers of a racemic drug. The use of a nonstereoselective assay method for a racemic compound can lead to difficulties in interpretation of data from, for example, bioequivalence or dose/concentration vs effect assessments. In this review data from a number of representative studies involving pharmacokinetics of chiral drugs are presented and discussed.

Gastrointestinal medications

Medications to address gastrointestinal disorders are among the most commonly dispensed somatic medications. The authors examine proton pump inhibitors, H(2) blockers, 5-HT(3) receptor-antagonists, and a few other drugs that are used to address this domain of medical concerns. The metabolic pathways, interactions with the P-glycoprotein transporter, and capabilities of inhibiting or inducing metabolic enzymes are elucidated for each drug. Specific drug-drug interactions with each agent are also detailed, including both psychotropic and non-psychotropic agents. Also, the article explores how different genotypic variants for specific cytochrome P450 enzymes have an impact on the effectiveness and likelihood of drug-drug interactions relating to specific gastro-intestinal medications.

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.

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.

Enantiomer/Enantiomer Interactions between theS- andR- Isomers of Omeprazole in Human Cytochrome P450 Enzymes: Major Role of CYP2C19 and CYP3A4

We investigated the enzyme kinetic basis for the stereoselective disposition of R- and S-omeprazole (OME) and racemic OME in human liver microsomes. OME is primarily metabolized by the hepatic cytochrome P450 enzyme system (CYP2C19 and 3A4). The metabolism of each enantiomer and pseudoracemic OME was studied using unlabeled and (13)C(7)-labeled enantiomers. The enantiomers inhibited each other's metabolism competitively in human liver microsomes and in recombinant CYP2C19 and 3A4. The results obtained with the individual enantiomers allowed successful prediction of the enzyme kinetics for the pseudoracemate. The intrinsic clearance of each enantiomer in a pseudoracemic mixture remained the same as those of the individually incubated enantiomers, although K(m) and V(max) decreased. In the pseudoracemate, the relative contribution of CYP2C19 and 3A4 to 5-hydroxylation and 5'-O-demethylation of R-OME was comparable to that obtained for the incubation of R-OME alone. For S-OME, however, the presence of its antipode greatly increased the contribution of CYP3A4, with increasing concentrations, compared with that obtained when incubating S-OME alone. The results of our in vitro study clearly show metabolic interactions between the OME enantiomers, which may also occur in vivo. Because the enantiomers of OME produce similar pharmacological effects, the enantiomer interactions should not significantly affect the pharmacodynamics. On the other hand, the use of the S-enantiomer results in less complex enzyme kinetics than those of the racemate; thus, the outcome of its clinical use is more predictable.

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.

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.

Stereoselective pharmacokinetics of RS-8359, a selective and reversible MAO-A inhibitor, by species-dependent drug-metabolizing enzymes

RS-8359, (+/-)-4-(4-cyanoanilino)-5,6-dihydro-7-hydroxy-7H-cyclopenta[d]pyrimidine selectively and reversibly inhibits monoamine oxidase A (MAO-A). After oral administration of rac-RS-8359 to rats, mice, dogs, monkeys, and humans, plasma concentrations of the (R)-enantiomer were greatly higher than were those of the (S)-enantiomer in all species studied. The AUC((R)) to AUC((S)) ratios were 2.6 in rats, 3.8 in mice, 31 in dogs, and 238 in monkeys, and the (S)-enantiomer was almost negligible in human plasma. After intravenous administration of RS-8359 enantiomers to rats, the pharmacokinetic parameters showed that the (S)-enantiomer had a 2.7-fold greater total clearance (CL(t)) and a 70% shorter half-life (t(1/2)) than those for the (R)-enantiomer but had no difference in distribution volume (V(d)). No significant difference in the intestinal absorption rate was observed. The principal metabolites were the 2-keto form, possibly produced by aldehyde oxidase, the cis-diol form, and the 2-keto-cis-diol form produced by cytochrome P450 in rats, the cis-diol form in mice, RS-8359 glucuronide in dogs, and the 2-keto form in monkeys and humans. Thus, the rapid disappearance of the (S)-enantiomer from the plasma was thought to be due to the rapid metabolism of the (S)-enantiomer by different drug-metabolizing enzymes, depending on species.

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.

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.

Simultaneous determination of lansoprazole enantiomers and their metabolites in plasma by liquid chromatography with solid-phase extraction

A simple and highly sensitive high-performance liquid chromatography (HPLC) method for the simultaneous quantitative determination of lansoprazole enantiomers and their metabolites, 5-hydroxylansoprazole enantiomers and lansoprazole sulfone, in human plasma have been developed. Chromatographic separation was achieved with a Chiral CD-Ph column using a mobile phase of 0.5M NaClO(4)-acetonitrile-methanol (6:3:1 (v/v/v)). The analysis required only 100 microl of plasma and involved a solid-phase extraction with Oasis HLB cartridge, with a high extraction recovery (>94.1%) and good selectivity. The lower limit of quantification (LOQ) of this assay was 10 ng/ml for each enantiomer of both lansoprazole and 5-hydroxylansoprazole, and 5 ng/ml for lansoprazole sulfone. The coefficient of variation of inter- and intra-day assay was <8.0% and accuracy was within 8.4% for all analytes (concentration range 10-1000 ng/ml). The linearity of this assay was set between 10 and 1000 ng/ml (r2>0.999 of the regression line) for each of the five analytes. This method is applicable for accurate and simultaneous monitoring of the plasma levels of lansoprazole enantiomers and their metabolites in the renal transplant recipients.

Stereoselective metabolism of lansoprazole by human liver cytochrome P450 enzymes

The stereoselective metabolism of lansoprazole enantiomers was evaluated by incubation of human liver microsomes and cDNA-expressed cytochrome p450 (p450) enzymes to understand and predict their stereoselective disposition in humans in vivo. The intrinsic clearances (Clint) of the formation of both hydroxy and sulfone metabolites from S-lansoprazole were 4.9- and 2.4-fold higher than those from the R-form, respectively. The sums of formation Clint of both metabolites were 13.5 and 57.3 microl/min/mg protein for R- and S-lansoprazole, respectively, suggesting that S-lansoprazole would be cleared more rapidly than the R-form. The p450 isoform selective inhibition study in liver microsomes, and the incubation study of cDNA-expressed enzymes, demonstrated that the stereoselective sulfoxidation is mediated by CYP3A4 and that the hydroxylation is mediated by CYP2C9 and CYP3A4 as well as by CYP2C19. Total Clint values of hydroxy and sulfone metabolite formation catalyzed by all these p450 enzymes were consistently higher for S-lansoprazole than for the R-form. The CYP3A4 produced the greatest difference of Clint between S- and R-enantiomers, mainly due to a difference of sulfoxidation metabolism (Clint 76.5 versus 10.8 microl/min/nmol of p450, respectively), whereas CYP2C19-catalyzed hydroxylation resulted in a minor difference of Clint between S- and R-enantiomers (179.6 versus 143.3 microl/min/nmol of p450, respectively). However, the affinity of CYP2C19 on hydroxylation was 5.7-fold higher for S-enantiomer than for the R-form (Km 2.3 versus 13.1 microM), suggesting that the role of CYP2C19 on stereoselective hydroxylation would be more prominent at concentrations around the usual therapeutic level. These findings suggest that both CYP2C19 and CYP3A4 are major enzymes contributing to the stereoselective disposition of lansoprazole, but stereoselective hydroxylation of lansoprazole enantiomers is mainly influenced by CYP2C19, especially at the usual therapeutic doses.

Different contribution of CYP2C19 in the in vitro metabolism of three proton pump inhibitors

A series of clinical studies on the cytochrome P450 2C19 (CYP2C19) genotype and the pharmacokinetics and pharmacodynamics of three proton pump inhibitors (PPIs), omeprazole, lansoprazole and rabeprazole, have been conducted to establish the individualized pharmacotherapy based on the CYP2C19 genotyping, and in the present study, the CYP2C19 genotype-dependency was more pronounced for omeprazole than the other two. Herein, to validate further the difference among 3 PPIs in CYP2C19 genotype-dependency on the phenotype, a comparative in vitro study was conducted using the human liver microsomes and newly developed anti-human CYP antibodies. The residual concentrations of omeprazole and lansoprazole in 5 lots of human liver microsomes were dependent on the CYP2C19 activities, however, for rabeprazole, there was no correlation. The hydroxylation of omeprazole was more inhibited by anti-CYP2C19 antibody than lansoprazole, whereas anti-CYP3A4 antibody showed similar inhibition. In conclusion, the relative contribution of CYP2C19 on total metabolism of 3 PPIs elucidated herein coincided with the CYP2C19 genotype-dependent pharmacokinetics.