Pharmacokinetics Of Repaglinide Research Articles

Drug-drug interaction between pachymic acid and repaglinide in rats and its potential mechanism

Both repaglinide and pachymic acid are useful for reducing blood glucose, but the drug interactions between them are not known. This study aimed to explore the effect of pachymic acid on the pharmacokinetics of repaglinide in rats and to elucidate its mechanism. The effects of pachymic acid (5 and 10 mg/kg) on the pharmacokinetics of repaglinide (0.5 mg/kg) were investigated in Sprague-Dawley rats (n = 6) with a single dose of repaglinide as a control. LC-MS/MS was used to determine the plasma concentration of repaglinide. Furthermore, the effect of pachymic acid on the metabolic stability of repaglinide and CYP3A4 activity was assessed in rat liver microsomes (RLMs). The co-administration of repaglinide and pachymic acid caused considerable changes in the pharmacokinetics of repaglinide, as shown by an increase in Cmax, t1/2, and AUC(0-t), and a decrease in CLz/F. The effect of pachymic acid was enhanced with increasing concentration. In vitro, pachymic acid showed a significant improvement of the metabolic stability of repaglinide in RLMs and inhibited the activity of CYP3A4. Co-administration of repaglinide with pachymic acid increased the systemic exposure of repaglinide and improved its metabolic stability in rats, which was mediated by CYP3A4. The results of animal studies cannot be directly applied to clinical practice, but concomitant administration of repaglinide and pachymic acid should be avoided or monitored until interaction studies are performed in humans.

Evaluation of Safety and Clinically Relevant Drug-Drug Interactions with Tucatinib in Healthy Volunteers.

Background and ObjectiveTucatinib is approved for treatment of human epidermal growth factor receptor 2-positive metastatic breast cancer. Understanding potential drug–drug interactions (DDIs) informs proper dosing when co-administering tucatinib with other therapies. The aim of this study was to evaluate DDIs between tucatinib and metabolizing enzymes and transporters in healthy volunteers.MethodsParts A–C assessed the impact of itraconazole (cytochrome P450 [CYP] 3A4 inhibitor), rifampin (CYP3A4/CYP2C8 inducer), or gemfibrozil (CYP2C8 inhibitor) on the pharmacokinetics of a single 300 mg dose of tucatinib administered orally and its primary metabolite, ONT-993. Parts D and E assessed the effect of steady-state tucatinib on the pharmacokinetics of repaglinide (CYP2C8 substrate), tolbutamide (CYP2C9 substrate), midazolam (CYP3A4 substrate), and digoxin (P-glycoprotein substrate).ResultsTucatinib area under the concentration–time curve from time 0 extrapolated to infinity (AUC0–inf) increased by ~ 1.3- and 3.0-fold with itraconazole and gemfibrozil, respectively, and decreased by 48% with rifampin, indicating that tucatinib is metabolized primarily by CYP2C8, and to a lesser extent via CYP3A. Tucatinib was a strong inhibitor of CYP3A (midazolam AUC0–inf increased 5.7-fold), a weak inhibitor of CYP2C8 and P-glycoprotein, and had no impact on CYP2C9-mediated metabolism in humans. Tucatinib was well tolerated, alone and with co-administered drugs.ConclusionThe potential DDIs identified here may be mitigated by avoiding concomitant use of tucatinib with strong CYP3A inducers, moderate CYP2C8 inducers, CYP3A substrates with a narrow therapeutic window (modifying substrate dose where concomitant use is unavoidable), and strong CYP2C8 inhibitors (decreasing tucatinib dose where concomitant use is unavoidable), or by reducing the dose of P-glycoprotein substrates with a narrow therapeutic window.Trial RegistrationThis trial (NCT03723395) was registered on October 29, 2018.Supplementary InformationThe online version contains supplementary material available at 10.1007/s40262-022-01144-z.

Effects of Aspirin on the Bioavailability and Pharmacokinetics of Repaglinide: Possible Role of Cytochrome P450 3A Isoforms Inhibition by Aspirin

Effects of Aspirin on the Bioavailability and Pharmacokinetics of Repaglinide: Possible Role of Cytochrome P450 3A Isoforms Inhibition by Aspirin

Effects of CYP2C8 and SLCO1B1 Genetic Polymorphisms on Repaglinide Pharmacokinetics: A Systematic Review and Meta-Analysis.

The purpose of this systematic review and meta-analysis was to summarize the potential impact of CYP2C8 and SLCO1B1 genetic polymorphisms on repaglinide pharmacokinetics. A systematic search was conducted using electronic databases. Eligible studies reported data from pharmacokinetic evaluations of repaglinide in healthy adults according to different categories of CYP2C8 and SLCO1B1 genetic polymorphisms. Six studies including a total of 191 participants met the inclusion criteria. We noted that CYP2C8 *1/*3 carriers exhibited lower AUC(0-∞) (SMD: -0.77; 95%CI: -1.23 to -0.30; P=0.001) and Cmax (SMD: -0.94; 95%CI: - 1.41 to -0.47; P<0.001) than CYP2C8 *1/*1 carriers. There were no significant differences in AUC(0-∞), Cmax, t1/2 and mean change in blood glucose concentration between *1/*4 and *1/*1 carriers. Further, *3/*3 carriers had lower Cmax (SMD: -1.42; 95%CI: -2.66 to -0.17; P=0.026) than *1/*1 carriers. Additionally, *3/*3 carriers had lower Cmax than *1/*3 carriers (SMD: -1.20; 95%CI: -2.40 to -0.00; P=0.050). Finally, we noted that repaglinide pharmacokinetics did not differ by SLCO1B1 genotype. The current systematic review and meta-analysis indicated that the genotype of CYP2C8, but not SLCO1B1, may affect repaglinide pharmacokinetics. However, because of the comparatively insufficient number of published studies included, our conclusions require support from additional studies.

Repaglinide-irbesartan drug interaction: effects of SLCO1B1 polymorphism on repaglinide pharmacokinetics and pharmacodynamics in Chinese population

On account of the potential inhibition of OATP1B1 (organic anion transporting polypeptide) by angiotensin II receptor blockers (ARBs) and the effects of SLCO1B1 (solute carrier organic anion transporter family member) polymorphism, the aim of current study is to assess the impact of ARBs on the pharmacokinetics (PK) and pharmacodynamics (PD) of repaglinide in Chinese healthy volunteers with different SLCO1B1 genotypes. The in vitro study was conducted on irbesartan, valsartan, olmesartan, and losartan by using HEK293 cells transfected with OATP1B1. Data on drug interactions between repaglinide and irbesartan from 21 healthy Chinese-Han male volunteers were collected and analyzed. IC50 from in vitro study suggested irbesartan was the most potent inhibitor of OATP1B1 transporter. Clinical data from single dose of repaglinide indicated SLCO1B1 c.521 T>C polymorphism influenced the PK and PD of repaglinide in healthy Chinese-Han male volunteers. In subjects with SLCO1B1 c.521 TT genotype, irbesartan comedication increased the exposure of repaglinide. In details, the peak plasma concentration [Cmax] increased 84% (P = 0.003) and the area under the curve of plasma concentration 0-8h [AUC0-8] increased 34% (P = 0.004), while the minimum blood glucose concentration [Cmin] decreased 33.8% (P = 0.005). No significant change was observed in repaglinide exposure in subjects with SLCO1B1 c.521 TC genotype in presence or absence of irbesartan. SLCO1B1 c.521 T>C polymorphism affects the PK of repaglinide in Chinese population. Irbesartan increased repaglinide exposure in subjects with SLCO1B1 c.521 TT genotype, but not SLCO1B1 c.521 TC genotype.

Impact of chronic unpredicted mild stress-induced depression on repaglinide fate via glucocorticoid signaling pathway.

Chronic unpredicted mild stress (CUMS)-induced depression could alter the pharmacokinetics of many drugs in rats, however, the underlying mechanism is not clear. In this work we studied the pharmacokinetics of repaglinide, and explored the role of glucocorticoid and adrenergic signaling pathway in regulating drug metabolizing enzymes (DMEs) in GK rats and BRL 3A cells. The plasma cortisol and epinephrine levels were increased, meanwhile the pharmacokinetics of repaglinide were altered significantly in depression model rats. Forty-nine genes in liver of model rats displayed significant difference comparing to control rats. The differentially expressed genes enriched in the drug metabolism and steroid hormone biosynthesis pathway significantly, and Nr1i3 matched 335 connectivity genes. CAR and Ugt1a1 protein expression were enhanced significantly in liver of model rats. The mRNA expression of Ugt1a1 and Nr1i2 were increased 2 and 4 times respectively with dexamethasone (DEX) and 8-Br-cAMP co-treatment in BRL 3A cells. The protein expression of PXR was up-regulated, too. However, RU486 reversed the up-regulated effect. The adrenergic receptor agonists had little impact on the DMEs in BRL 3A. Our data suggested that CUMS-induced depression might up-regulate DMEs expression via glucocorticoid signaling pathway, and accelerate the fate of the repaglinide in spontaneous diabetes rats.

&amp;lt;i&amp;gt;In Vitro&amp;lt;/i&amp;gt; and &amp;lt;i&amp;gt;in Vivo&amp;lt;/i&amp;gt; (Mouse) Evaluation of Drug-Drug Interactions of Repaglinide with Anti-HIV Drugs

Repaglinide is type 2 short acting anti-diabetic drug which is primarily metabolized by CYP2C8 and CYP3A4 and is also a substrate of influx transporter OATP1B1. HIV drugs are potent inhibitors of CYP3A4 and OATP transporters. Several drug-drug interactions (DDIs) were noticed when protease inhibitors (PIs) coadministered with drugs metabolized by CYP3A4. The PIs are also potent mechanism based inhibitors, out which ritonavir is most potent. In the current study we evaluated in vitro (mouse and human liver microsomes) and in vivo DDIs of repaglinide with anti-HIV drugs. Out of the following tested drugs (Amprenavir, Indinavir, Nelfinavir, Ritonavir, Saquinavir, Delavirdine, Maraviroc, Efavirenz, Nevirapine and Ketoconazole) Amprenavir (APV), Ritonavir (RTV) and Ketoconazole (KTZ) showed inhibition of OH-repaglinide formation in human and mouse liver microsomes. The positive reversible inhibitions were further tested for irreversible inhibitions where we didn’t observe any irreversible inhibitions. In vitro inhibitions were further evaluated in the in vivo pharmacokinetics (mouse) where repaglinide pharmacokinetics was altered by RTV and KTZ. The DDIs in both studies were very strong; the dose of repaglinide is reduced to 20 fold. In conclusion, there could be possible DDIs when RTV dosed with repaglinide; we have also demonstrated that mouse could be useful preclinical tool when used in conjunction with in vitro screening models for DDIs.

Reduced Physiologically-Based Pharmacokinetic Model of Repaglinide: Impact of OATP1B1 and CYP2C8 Genotype and Source of In Vitro Data on the Prediction of Drug-Drug Interaction Risk

To investigate the effect of OATP1B1 genotype as a covariate on repaglinide pharmacokinetics and drug-drug interaction (DDIs) risk using a reduced physiologically-based pharmacokinetic (PBPK) model. Twenty nine mean plasma concentration-time profiles for SLCO1B1 c.521T>C were used to estimate hepatic uptake clearance (CLuptake) in different genotype groups applying a population approach in NONMEM v.7.2. Estimated repaglinide CLuptake corresponded to 217 and 113μL/min/10(6) cells for SLCO1B1 c.521TT/TC and CC, respectively. A significant effect of OATP1B1 genotype was seen on CLuptake (48% reduction for CC relative to wild type). Sensitivity analysis highlighted the impact of CLmet and CLdiff uncertainty on the CLuptake optimization using plasma data. Propagation of this uncertainty had a marginal effect on the prediction of repaglinide OATP1B1-mediated DDI with cyclosporine; however, sensitivity of the predicted magnitude of repaglinide metabolic DDI was high. In addition, the reduced PBPK model was used to assess the effect of both CYP2C8*3 and SLCO1B1 c.521T>C on repaglinide exposure by simulations; power calculations were performed to guide prospective DDI and pharmacogenetic studies. The application of reduced PBPK model for parameter optimization and limitations of this process associated with the use of plasma rather than tissue profiles are illustrated.

Effects of nifedipine on the pharmacokinetics of repaglinide in rats: Possible role of CYP3A4 and P-glycoprotein inhibition by nifedipine

BackgroundThe aim of this study was to investigate the effects of nifedipine on the bioavailability and pharmacokinetics of repaglinide in rats. MethodsThe effect of nifedipine on P-glycoprotein (P-gp) and cytochrome P450 (CYP) 3A4 activity was evaluated. The pharmacokinetic parameters of repaglinide and blood glucose concentrations were also determined in rats after oral (0.5mg/kg) and intravenous (0.2mg/kg) administration of repaglinide to rats in the presence and absence of nifedipine (1 and 3mg/kg). ResultsAdministration of nifedipine resulted in inhibition CYP3A4 activity with an IC50 value of 7.8μM, and nifedipine significantly inhibited P-gp activity in a concentration-dependent manner. Compared to the oral control group, nifedipine significantly increased the area under the plasma concentration-time curve (AUC0–∞) and the peak plasma concentration (Cmax) of repaglinide by 49.3 and 25.5%, respectively. Nifedipine significantly decreased the total body clearance (CL/F) of repaglinide by 22.0% compared to the oral control group. Nifedipine also increased the absolute bioavailability (AB) of repaglinide by 50.0% compared to the oral control group (33.6%). In addition, the relative bioavailability (RB) of repaglinide was 1.16- to 1.49-fold greater than that of the control group. Compared to the intravenous control, nifedipine significantly increased AUC0–∞ of repaglinide. Blood glucose concentrations had significant differences compared to the oral control groups. ConclusionNifedipine enhanced the oral bioavailability of repaglinide, which may be mainly attributable to inhibition of CYP3A4-mediated metabolism of repaglinide in the small intestine and/or in the liver and to inhibition of the P-gp efflux transporter in the small intestine and/or reduction of total body clearance by nifedipine. The current study has raised awareness of potential drug interactions by concomitant use of repaglinide with nifedipine.

Mechanistic Modeling to Predict the Transporter- and Enzyme-Mediated Drug-Drug Interactions of Repaglinide

Quantitative prediction of complex drug-drug interactions (DDIs) is challenging. Repaglinide is mainly metabolized by cytochrome-P-450 (CYP)2C8 and CYP3A4, and is also a substrate of organic anion transporting polypeptide (OATP)1B1. The purpose is to develop a physiologically based pharmacokinetic (PBPK) model to predict the pharmacokinetics and DDIs of repaglinide. In vitro hepatic transport of repaglinide, gemfibrozil and gemfibrozil 1-O-β-glucuronide was characterized using sandwich-culture human hepatocytes. A PBPK model, implemented in Simcyp (Sheffield, UK), was developed utilizing in vitro transport and metabolic clearance data. In vitro studies suggested significant active hepatic uptake of repaglinide. Mechanistic model adequately described repaglinide pharmacokinetics, and successfully predicted DDIs with several OATP1B1 and CYP3A4 inhibitors (<10% error). Furthermore, repaglinide-gemfibrozil interaction at therapeutic dose was closely predicted using in vitro fraction metabolism for CYP2C8 (0.71), when primarily considering reversible inhibition of OATP1B1 and mechanism-based inactivation of CYP2C8 by gemfibrozil and gemfibrozil 1-O-β-glucuronide. This study demonstrated that hepatic uptake is rate-determining in the systemic clearance of repaglinide. The model quantitatively predicted several repaglinide DDIs, including the complex interactions with gemfibrozil. Both OATP1B1 and CYP2C8 inhibition contribute significantly to repaglinide-gemfibrozil interaction, and need to be considered for quantitative rationalization of DDIs with either drug.

Effects of Fluvastatin on the Pharmacokinetics of Repaglinide: Possible Role of CYP3A4 and P-glycoprotein Inhibition by Fluvastatin

The purpose of this study was to investigate the effects of fluvastatin on the pharmacokinetics of repaglinide in rats. The effect of fluvastatin on P-glycoprotein and CYP3A4 activity was evaluated. The pharmacokinetic parameters and blood glucose concentrations were also determined after oral and intravenous administration of repaglinide to rats in the presence and absence of fluvastatin. Fluvastatin inhibited CYP3A4 activity in a concentration-dependent manner with a 50% inhibition concentration(IC50) of 4.1 µM and P-gp activity. Compared to the oral control group, fluvastatin significantly increased the AUC and the peak plasma level of repaglinide by 45.9% and 22.7%, respectively. Fluvastatin significantly decreased the total body clearance (TBC) of repaglinide compared to the control. Fluvastatin also significantly increased the absolute bioavailability (BA) of repaglinide by 46.1% compared to the control group. Moreover, the relative BA of repaglinide was 1.14- to 1.46-fold greater than that of the control. Compared to the i.v. control, fluvastatin significantly increased the AUC0-∞ of i.v. administered repaglinide. The blood glucose concentrations showed significant differences compared to the oral controls. Fluvastatin enhanced the oral BA of repaglinide, which may be mainly attributable to the inhibition of the CYP3A4-mediated metabolism of repaglinide in the small intestine and/or liver, to the inhibition of the P-gp efflux transporter in the small intestine and/or to the reduction of TBC of repaglinide by fluvastatin. The study has raised the awareness of potential interactions during concomitant use of repaglinide with fluvastatin. Therefore, the concurrent use of repaglinide and fluvastatin may require close monitoring for potential drug interactions.

2012 American College of Clinical Pharmacology Annual Meeting September 23rd–25th San Diego, California

2012 American College of Clinical Pharmacology Annual Meeting September 23^rd–25^th San Diego, California

The Influence of MDR1 G2677T/A Genetic Polymorphisms on the Pharmacokinetics of Repaglinide in Healthy Chinese Volunteers

Aims: The aim of this study was to evaluate the pharmacogenetic variability in the disposition of repaglinide in healthy Chinese subjects. Methods: A single dose of 2 mg repaglinide was orally administered to 24 healthy Chinese subjects. The serum concentrations of repaglinide were measured by using liquid chromatography/tandem mass spectrometry. We determined the polymorphic alleles of MDR1 C1236T, MDR1 G2677T/A, MDR1 C3435T, CYP3A4*18, OATP1B1 G388A, and OATP1B1 T521C in each subject. Results: The area under the plasma concentration-time curve from time 0 to infinity (AUC_(0–inf)) of repaglinide was significantly higher in subjects possessing the MDR1 2677GT and 2677TT alleles than in those with the MDR1 2677GG and 2677TA alleles (p = 0.007). The mean AUCs and peak plasma concentration were higher in subjects with the 521TC allele than in those with the OATP1B1 521TT allele, and the OATP1B1 388A allele is associated with a reduced trend of pharmacokinetic exposure; however, these trends were not statistically significant. The pharmacokinetics of repaglinide was not associated with MDR1 C1236T, MDR1 C3435T, and CYP3A4*18. Conclusion: This study shows that the genetic polymorphisms of MDR1 G2677T/A might explain the variability in the pharmacokinetics of repaglinide in the Chinese population.

G-011 INFLUENCE OF PITAVASTARIN AND SLCO1B1 POLYMORPHISMS ON REPAGLINIDE PHARMACOKINETICS AND PHARMACODYNAMICS IN HEALTHY CHINESE MALE SUBJECTS

Background This study investigated the effect of pitavastatin and SLCO1B1 genetic polymorphisms on the pharmacokinetics and pharmacodynamics of repaglinide. Methods In a randomized, placebo-controlled, crossover study, twelveSLCO1B1-genotyped healthy Chinese male volunteers were given daily doses of 4 mg pitavastatin or placebo for 5 days, followed by 4 mg oral dose of repaglinide on day 5. Plasma concentrations of repaglinide and blood glucose were measured by liquid chromatography-tandem mass spectrometry (LC/MS/MS) system and glucose oxidase method, respectively. Pharmacokinetic parameters were obtained by DAS Ver 2.0. Results Pitavastatin increased the peak plasma concentration (Cmax) of repaglinide significantly (P = 0.003), and the increase in Cmax was limited to participants with the SLCO1B1*1b/*1b genotype (P = 0.015) and carriers of the SLCO1B1*15 haplotype (P = 0.031). Pitavastatin can also increased the area under plasma concentration–time curve from 0 h to infinity (AUC0→∞) of repaglinide slightly (P = 0.091). No significant difference in the pharmacokinetic parameters and blood glucose-lowering effects of repaglinide were observed among SLCO1B1 genotype groups in either the placebo- or the pitavastatin-treatment phase. Conclusion Pitavastatin increased plasma concentrations of repaglinide in an SLCO1B1 genotype dependent manner, but had no effect on the pharmacodynamics of repaglinide in healthy volunteers.

Pharmacokinetic Interaction between Nisoldipine and Repaglinide in Rats

The purpose of this study was to investigate the effects of nisoldipine on the pharmacokinetics of repaglinide in rats. The effect of nisoldipine on cytochrome P450 (CYP) 3A4 activity and P-glycoprotein (P-gp) were evaluated. The pharmacokinetic parameters of repaglinide were also determined in rats after oral (0.5 mg · kg −1 ) and intravenous (0.2 mg · kg −1 ) administration of repaglinide to rats without or with nisoldipine (0.3 and 1.0 mg · kg −1 ). Nisoldipine inhibited CYP3A4 enzyme activity with a 50% inhibition concentration of 5.5 μM. In addition, nisoldipine signifi cantly enhanced the cellular accumulation of rhodamine-123 in MCF-7/ADR cells overexpressing P-gp. Compared to the oral control group, nisoldipine signifi cantly increased the AUC 0−∞ and the C max of repaglinide by 46.9% and 24.9%, respectively. Nisoldipine also increased the absolute bioavailability (A.B.) of repaglinide by 47.0% compared to the oral control group. Moreover, the relative bioavailability (R.B.) of repaglinide was 1.16- to 1.47-fold greater than that of the control group. Nisoldipine enhanced the oral bioavailability of repaglinide, which may be attributable to the inhibition of the CYP3A4-mediated metabolism in the small intestine and/or in the liver and to inhibition of P-gp in the small intestine rather than to reduction of renal elimination of repaglinide by nisoldipine. The increase in the oral bioavailability of repaglinide should be taken into consideration of potential drug interactions when co-administering repaglinide and nisoldipine.

Effects of SLCO1B1 polymorphisms on the pharmacokinetics and pharmacodynamics of repaglinide in healthy Chinese volunteers

Repaglinide is commonly used in the treatment of patients with type 2 diabetes mellitus to reduce postprandial hyperglycemia. The objective of this research was to study the effects of SLCO1B1 polymorphisms on the pharmacokinetics and pharmacodynamics of repaglinide in healthy Chinese volunteers. A total of 22 healthy young male participants were recruited from a pool of pharmacogenetically characterized participants genotyped for SLCO1B1, CYP3A4, and CYP2C8 SNPs by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). Volunteers with CYP2C8*3 and CYP3A4*4 alleles were excluded from the clinical study. Then selected volunteers took part in the clinical pharmacokinetic study, receiving 2mg repaglinide. Healthy participants with SLCO1B1*1A/*1B or *1A/*1A genotype and SLCO1B1 *15/*1A or *5/*1A genotype had significantly higher AUC(0-∞) than participants with SLCO1B1*1B/*1B genotype, with the former showing an increase over the latter of 39.81 and 42.09%, respectively (P = 0.028, 0.032). The clearance in the former two genotype groups was significantly attenuated (by 27.39 and 28.55%, respectively) compared with individuals with SLCO1B1*1B/*1B genotype (P = 0.015, 0.019). No significant differences in blood glucose-lowering effect were observed among three genotype groups. SLCO1B1*1B/*1B genotype is associated with reduced pharmacokinetic exposure after a single dose oral administration of 2mg repaglinide, including decreased AUC(0-∞) and increased clearance of repaglinide. Moreover, this polymorphism of SLCO1B1 has significant influence on the pharmacokinetics of repaglinide, but no effects on its pharmacodynamics.

Effect of theCYP2C8Genotype on the Pharmacokinetics and Pharmacodynamics of Repaglinide

The pharmacokinetics of repaglinide shows pronounced interindividual variability, for which several reasons have been considered, including interactions with drugs inhibiting CYP2C8 and CYP2C8 genetic polymorphism. However, existing data on the role of genetic polymorphisms in repaglinide disposition are not fully consistent. We studied the effect of CYP2C8*3 on the pharmacokinetics and pharmacodynamics of repaglinide in 29 healthy whites carrying CYP2C8*3/*3 (n = 4), CYP2C8*1/*3 (n = 13), or CYP2C8*1/*1 (n = 12). After administration of a single dose of 2 mg of repaglinide, blood was drawn for assessment of repaglinide pharmacokinetics and pharmacodynamics, and urine was collected to quantify the main repaglinide metabolites M1 and M4 up to 24 h postdose. Repaglinide and the metabolites were quantified by liquid chromatography-tandem mass spectrometry. Considering only the effect of CYP2C8*3, the mean (95% confidence interval) area under the time-concentration curve (AUC) from zero to infinity of repaglinide was 72.4 (6.7-138.0), 97.2 (59.2-135.2), and 105.9 (52.4-159.3) ng · ml(-1) · h and the maximal concentration (C(max)) was 38.5 (3.8-73.2), 50.3 (37.5-63.0), and 60.3 (31.5-89.1) ng · ml(-1), respectively, in carriers of CYP2C8*3/*3, CYP2C8*1/*3, and CYP2C8*1/*1 [p > 0.05, one-way analysis of variance (ANOVA)]. In addition, for urinary metabolite excretion and pharmacodynamic parameters, i.e., mean and maximal changes in insulin and glucose concentration, no significant differences between CYP2C8 genotypes were observed. Likewise, no significant effects on the pharmacokinetics or pharmacodynamics were observed when AUC and C(max) of repaglinide were corrected for reported effects of the SLCO1B1 521T>C polymorphism or when both polymorphisms were tested in a two-way ANOVA. In conclusion, CYP2C8*3 does not seem to play an important role in the pharmacokinetics and pharmacodynamics of repaglinide given in a therapeutic dose.

Association between Sex Differences and the Pharmacokinetics of Repaglinide among a Malaysian Population

This study was conducted to evaluate the effect of sex differences on the pharmacokinetics of repaglinide in healthy subjects. One hundred twenty one healthy volunteers (61 male and 60 female; aged 18 - 50 years) were included in the study. Subjects were administered a single 4-mg repaglinide oral dose. Blood samples were taken at 0, 30, 60, 120, 180 and 240 min. Serum repaglinide levels were determined by a high-performance liquid chromatography (HPLC) method. Subjects were also genotyped by polymerase chain reactions - restriction fragment length polymorphisms (PCR-RFLP) for CYP3A4*4, *5 and *18 alleles and by an allele-specific multiplex PCR for CYP2C8*2, *3, *4 and *5 alleles. The pharmacokinetics of repaglinide were comparable between male and female subjects. The mean clearance (CL) of repaglinide was 16.0% lower (p = 0.03), the mean area under the serum concentration-time curve (AUC) was 12.8% higher (p = 0.04) and the peak serum concentration (Cmax) was 13.2% higher (p = 0.03) in females compared to male subjects. The mean rate of elimination (kel) and mean CL of repaglinide were 47.67% (p = 0.03) higher and 29.25% (p = 0.03) higher, respectively, in male subjects having CYP2C8*5 allele compared to female subjects. We also found that the mean half-life (t1/2) of repaglinide was 42.43% higher (p = 0.03), and the mean AUC was 35.83% higher (p = 0.03) in female subjects when compared to the male subjects having CYP2C8*5 allele. Sex differences significantly influence the pharmacokinetics of repaglinide.

The effect of SLCO1B1 polymorphism on repaglinide pharmacokinetics persists over a wide dose range

To establish whether the effect of SLCO1B1[encoding organic anion transporting polypeptide 1B1 (OATP1B1)] c.521T-->C (p.Val174Ala) polymorphism on the pharmacokinetics of repaglinide is dose-dependent. Twelve healthy volunteers with the SLCO1B1 c.521TT genotype (controls) and eight with the c.521CC genotype ingested a single 0.25-, 0.5-, 1- or 2-mg dose of repaglinide in a dose-escalation study with a wash-out period of > or =1 week. The mean area under the plasma concentration-time curve from time 0 to infinity (AUC(0-infinity)) of 0.25, 0.5, 1 or 2 mg repaglinide was 82% (95% confidence interval 47, 125), 72% (24, 138), 56% (24, 95) or 108% (59, 171) (P < or = 0.001) larger in participants with the SLCO1B1 c.521CC genotype than in those with the c.521TT genotype, respectively. Repaglinide peak plasma concentration and AUC(0-infinity) increased linearly along with repaglinide dose in both genotype groups (r > 0.88, P < 0.001). There was a tendency towards lower blood glucose concentrations after repaglinide administration in the participants with the c.521CC genotype than in those with the c.521TT genotype. The effect of SLCO1B1 c.521T-->C polymorphism on the pharmacokinetics of repaglinide persists throughout the clinically relevant dose range.

Effects of Gemfibrozil and Atorvastatin on the Pharmacokinetics of Repaglinide in Relation to SLCO1B1 Polymorphism

In a randomized crossover study, 24 SLCO181-genotyped healthy volunteers were given daily doses of 1,200 mg gemfibrozil, 40 mg atorvastatin, or placebo, followed by 0.25 mg of repaglinide on day 3. The mean increase in the repaglinide area under the plasma concentration-time curve from 0 h to infinity (AUC(0-infinity)) produced by gemfibrozil was larger in individuals with the SLCO1B1 c.521CC genotype (n = 6) than in those with the c.521TC (n = 6) and c.521TT (n = 12) genotypes, by factors of 1.56 (P = 0.004) and 1.54 (P = 0.002), respectively. Gemfibrozil prolonged the repaglinide elimination half-life 1.43 times more in the c.521 CC group than in the c.521TT group (P = 0.047), but no differences were seen in the effects on peak plasma concentration (C(max)). While on gemfibrozil, the minimum blood glucose concentration after repaglinide intake was 19% lower in the c.521CC participants than in the c.521TT participants (P = 0.009). In the c.521TT group, atorvastatin intake had the effect of increasing repaglinide Cmax and AUC(0-infinity) by41% (P = 0.001) and 18% (P = 0.033), respectively. In conclusion, the extent of gemfibrozil-repaglinide interaction depends on SLCO1B1 genotype. Atorvastatin raises plasma repaglinide concentrations, probably by inhibiting organic anion transporting polypeptide 1B1 (OATP1B1).