Clinical pharmacokinetics and pharmacodynamics of repaglinide

A comprehensive review of small-molecule drugs for the treatment of type 2 diabetes mellitus: Synthetic approaches and clinical applications

Type 2 diabetes mellitus (T2DM) is a long-term metabolic disorder characterized by the body's resistance to insulin and inadequate production of insulin. Small molecule drugs to treat T2DM mainly control blood sugar levels by improving insulin sensitivity, increasing insulin secretion, or reducing liver glycogen production. With the deepening of research on the pathogenesis of diabetes, many drugs with new targets and mechanisms of action have been discovered. The targets of the drugs for T2DM are mainly dipeptidyl peptidase IV inhibitors (DPP4), sodium/glucose cotransporter 2 inhibitors (SGLT2), sulfonylurea receptor modulators (SUR), peroxisome proliferator-activated receptor γ agonists (PPARγ), etc. We are of the opinion that acquiring a comprehensive comprehension of the synthetic procedures employed in drug molecule production will serve as a source of inventive and pragmatic inspiration for the advancement of novel, more potent, and feasible synthetic methodologies. This review aims to outline the clinical applications and synthetic routes of some representative drugs to treat T2DM, which will drive the discovery of new, more effective T2DM drugs.

Formulation and Optimization of Repaglinide Nanoparticles Using Microfluidics for Enhanced Bioavailability and Management of Diabetes

The technologies for fabrication of nanocrystals have an immense potential to improve solubility of a variety of the poor water-soluble drugs with subsequent enhanced bioavailability. Repaglinide (Rp) is an antihyperglycemic drug having low bioavailability due to its extensive first-pass metabolism. Microfluidics is a cutting-edge technique that provides a new approach for producing nanoparticles (NPs) with controlled properties for a variety of applications. The current study’s goal was to engineer repaglinide smart nanoparticles (Rp-Nc) utilizing microfluidic technology (Dolomite Y shape), and then to perform in-vitro, in-vivo, and toxicity evaluations of them. This method effectively generated nanocrystals with average particle sizes of 71.31 ± 11 nm and a polydispersity index (PDI) of 0.072 ± 12. The fabricated Rp’s crystallinity was verified by Differential scanning calorimetry (DSC) and Powder X-ray diffraction (PXRD). In comparison to the raw and commercially available tablets, the fabricated Rp’s nanoparticles resulted in a higher saturation solubility and dissolving rate (p < 0.05). Rp nanocrystals had a considerably lower (p < 0.05) IC50 value than that of the raw drug and commercial tablets. Moreover, Rp nanocrystals at the 0.5 and 1 mg/kg demonstrated a significant decrease in blood glucose level (mg/dL, p < 0.001, n = 8) compared to its counterparts. Rp nanocrystals at the 0.5 mg/kg demonstrated a significant decrease (p < 0.001, n = 8) in blood glucose compared to its counterparts at a dose of 1 mg/kg. The selected animal model’s histological analyses and the effect of Rp nanocrystals on several internal organs were determined to be equivalent to those of the control animal group. The findings of the present study indicated that nanocrystals of Rp with improved anti-diabetic properties and safety profiles can be successfully produced using controlled microfluidic technology, an innovative drug delivery system (DDS) approach.

Pharmacotherapy of type 2 diabetes: An update and future directions

Type 2 diabetes (T2D) is a widely prevalent disease with substantial economic and social impact for which multiple conventional and novel pharmacotherapies are currently available; however, the landscape of T2D treatment is constantly changing as new therapies emerge and the understanding of currently available agents deepens. This review aims to provide an updated summary of the pharmacotherapeutic approach to T2D. Each class of agents is presented by mechanism of action, details of administration, side effect profile, cost, and use in certain populations including heart failure, non-alcoholic fatty liver disease, obesity, chronic kidney disease, and older individuals. We also review targets of novel therapeutic T2D agent development. Finally, we outline an up-to-date treatment approach that starts with identification of an individualized goal for glycemic control then selection, initiation, and further intensification of a personalized therapeutic plan for T2D.

Recent solubility and dissolution enhancement techniques for repaglinide a BCS class II drug: a review

Repaglinide is an oral blood-glucose-lowering drug used to manage type-2 diabetes mellitus by lowering post-prandial glucose by stimulating insulin secretion from pancreatic beta cells.

According to the biopharmaceutical classification system, repaglinide falls under the class II category. For such drugs, limited solubility and poor dissolution rate are the major hurdles to overcome by formulation scientists, as they hinder drug absorption and lead to inadequate therapeutic effects.

Therefore, this review aims to discuss in depth the various approaches investigated in the past five years to improve the solubility and dissolution of orally administered repaglinide: namely, solid dispersion, co-amorphous technology, cyclodextrin complexation, phospholipid complexes and polymeric micelles, nanocrystals, nanosuspensions and nanofibers.

Intranasal versus intraperitoneal Myrj 59-stabilized cubosomes: A potential armamentarium of effective anti-diabetic therapy

The present study is concerned with the suitability of using Myrj 59, out-performing the commonly used stabilizer i.e., poloxamer, for preparation of cubosomes on one hand and gives an insight into the need for distinctive choice of delivery system and administration route towards better diabetes pharmacotherapy on the other hand. In light, repaglinide (REP) cubosomal dispersion and in-situ gel forms were prepared and physicochemically characterized. The selected cubosomal forms were tested for in-vitro drug release and administered via intranasal (IN) and intraperitoneal (IP) routes and compared with Intravenous (IV) REP solution regarding in-vivo antidiabetic efficacy. The results confirmed the formation of cubic nanostructures (170-233 nm), entrapping high REP amounts (93.2-95.66 %). Sustained REP release from selected cubosomal forms was realized with no burst release. Upon in-vivo assessment, IN and IP REP cubosomes and cubosomal gel exhibited superior long-acting in-vivo traits over IV REP solution, respecting percentages of maximum reduction, total decrease in BG levels, and the pharmacological availability. Moreover, IP REP cubosomes and cubosomal gel revealed higher values of the aforementioned parameters than IN counterparts. In conclusion, IN and IP administration of the newly developed cubosomal forms could proffer feasible options for an optimal control of BG levels.

Evaluation of the Utility of PXB Chimeric Mice for Predicting Human Liver Partitioning of Hepatic Organic Anion-Transporting Polypeptide Transporter Substrates

The ability to predict human liver-to-plasma unbound partition coefficient (K_puu) is important to estimate unbound liver concentration for drugs that are substrates of hepatic organic anion-transporting peptide (OATP) transporters with asymmetric distribution into the liver relative to plasma. Herein, we explored the utility of PXB chimeric mice with humanized liver that are highly repopulated with human hepatocytes to predict human hepatic disposition of OATP substrates, including rosuvastatin, pravastatin, pitavastatin, valsartan, and repaglinide. In vitro total uptake clearance and transporter-mediated active uptake clearance in C57 mouse hepatocytes were greater than in PXB chimeric mouse hepatocytes for rosuvastatin, pravastatin, pitavastatin, and valsartan. Consistent with in vitro uptake data, enhanced hepatic uptake and resulting total systemic clearance were observed with the above four compounds in severely compromised immune-deficient (SCID) control mice compared with the PXB chimeric mice, which suggest that mouse has a stronger transporter-mediated hepatic uptake than human. In vivo liver-to-plasma K_puu from PXB chimeric and SCID control mice were also compared, and rosuvastatin and pravastatin K_puu in SCID mice were more than 10-fold higher than that in PXB chimeric mice, whereas pitavastatin, valsartan, and repaglinide K_puu in SCID mice were comparable with K_puu in PXB chimeric mice. Finally, PXB chimeric mouse liver-to-plasma K_puu values were compared with the reported human K_puu, and a good correlation was observed as the PXB K_puu vales were within 3-fold of human K_puu Our results indicate that PXB mice could be a useful tool to delineate hepatic uptake and enable prediction of human liver-to-plasma K_puu of hepatic uptake transporter substrates. SIGNIFICANCE STATEMENT: We evaluated PXB mouse with humanized liver for its ability to predict human liver disposition of five organic anion-transporting polypeptide transporter substrates. Both in vitro and in vivo data suggest that mouse liver has a stronger transporter-mediated hepatic uptake than the humanized liver in PXB mouse. More importantly, PXB liver-to-plasma unbound partition coefficient (K_puu) values were compared with the reported human K_puu, and a good correlation was observed. PXB mice could be a useful tool to project human liver-to-plasma K_puu of hepatic uptake transporter substrates.

The Impact of Surfactant Composition and Surface Charge of Niosomes on the Oral Absorption of Repaglinide as a BCS II Model Drug

Background

Niosomes, bilayer vesicles formed by the self-assembly of nonionic surfactants, are receiving increasing attention as potential oral drug delivery systems but the impact of niosomal formulation parameters on their oral capability has not been studied systematically. The aim of this study was to investigate the impact of surfactant composition and surface charge of niosomes in enhancing oral bioavailability of repaglinide (REG) as a BCS II model drug.

Methods

Niosomes (13 formulations) from various nonionic surfactants having HLB in the range of 4–28 (Tweens, Spans, Brijs, Myrj, poloxamer 188, TPGS and Labrasol) were prepared and characterized concerning their loading efficiency, hydrodynamic diameter, zeta potential, drug release profile, and stability. The oral pharmacokinetics of the selected formulations were studied in rats (8 in vivo groups).

Results

The results revealed that type of surfactant markedly affected the in vitro and in vivo potentials of niosomes. The C_max and AUC values of REG after administration of the selected niosomes as well as the drug suspension (as control) were in the order of Tween 80> TPGS> Myrj 52> Brij 35> Span 60≈Suspension. Adding stearyl amine as a positive charge-inducing agent to the Tween 80-based niosomes, resulted in an additional increase in drug absorption and values of AUC and C_max were 3.8- and 4.7-fold higher than the drug suspension, respectively.

Conclusion

Cationic Tween 80-based niosomes may represent a promising platform to develop oral delivery systems for BCS II drugs.

Spray dried solid dispersion of repaglinide using hypromellose acetate succinate: in vitro and in vivo characterization

OBJECTIVE

This research study attempted to develop spray-dried solid dispersion, to enhance the solubility of repaglinide, an antidiabetic drug.

SIGNIFICANCE

Aqueous solubility plays a major role in drug delivery because any chemical entity has to be in a dissolved state at the site of absorption, in order to get absorbed. Solid dispersion (SD) is one of the widely used techniques to enhance solubility and hence dissolution rate of poorly soluble drugs.

METHODS

Repagnilide, in hypromellose acetate succinate (HPMCAS) solution, was dried by spray drying to obtain spray-dried solid dispersion (SDSD). Plackett-Burman and Box-Behnken designs were used for screening formulation as well as process parameters, and optimization respectively. DSC, XRD, SEM were carried out to confirm the preparation of solid dispersion. SDSD was evaluated for in vitro dissolution, flow properties, Percentage yield and in vivo oral glucose tolerance test.

RESULT

Spray dried solid dispersion comprising (w/w) drug:polymer ratio of 1:3.82, 2.56% of aerosil and inlet temperature of 90 °C, corresponded to the best formulation obtained in this work. It showed t ₈₅% of less than 15 min and a significant reduction in blood glucose level in rats as compared to pure drug and marketed formulation.

CONCLUSION

Thus, it can be concluded that spray-dried solid dispersion prepared using HPMCAS is a useful technique for solubility and dissolution enhancement of repaglinide.

Drug-drug interactions when treating HIV-related metabolic disorders

Introduction: Drug-drug interactions (DDI) between antiretroviral drugs and drugs for the treatment of metabolic disturbances in people living with human immunodeficiency virus (HIV) (PLWH) have represented a problem of paramount importance in the recent times. The problem has been mainly driven by sharing common metabolizing pathways. This problem has classically been worsened by the frequent use of pharmacokinetic boosters to enhance protease inhibitors and some integrase inhibitors plasma levels. Areas covered: This article focuses on the interactions between antiretroviral drugs and those drugs used to treat metabolic disturbances which frequently appear in PLWH. These include dyslipidemia, diabetes mellitus, hyperuricemia, and finally, drugs for the treatment of overweight and clinical obesity. References from PubMed, Embase, or Web of Science, among others, were reviewed. Expert opinion: The advent of safer drugs, in terms of DDI, in the antiretroviral and the metabolic field,such as non-boosted antiretrovirals and drugs with divergent metabolizing paths. Besides, learning by the caregivers on how to decrease and manage DDI, together with the extensive use of online updated DDI databases, has undoubtedly minimized the problem. The foreseeable increase in the burden of HIV-associated comorbidities and their associated treatments anticipates further complexities in the management of DDI in PLWH.

Improved oral bioavailability of repaglinide, a typical BCS Class II drug, with a chitosan-coated nanoemulsion

The aim of the present study was to develop modified nanoemulsions to improve the oral bioavailability and pharmacokinetics of a poor water-soluble drug, repaglinide (RPG). The repaglinide-loaded nanoemulsions (RPG-NEs) were prepared from olive oil as internal phase, span 80, tween 80, and poloxamer 188 as emulsifiers, using homogenization technique. The mean droplet size, zeta potential, and entrapment efficiency of RPG-NEs were 86.5 ± 3.4 nm, -33.8 ± 2.1 mV, and 96.3 ± 2.3%, respectively. The chitosan-coated RPG-NEs (Cs-RPG-NEs) showed an average droplet size of 149.3 ± 3.9 nm and a positive zeta-potential of +31.5 ± 2.8 mV. Drug release profile of RPG-NEs was significantly higher than free drug in the simulated gastrointestinal fluids (p < .005). The in vivo study revealed 3.51- and 1.78-fold increase in the AUC_0-12h and C_max of the drug, respectively, in RPG-NEs-receiving animals in comparison to the free drug. The pharmacokinetic analysis confirmed that Cs-RPG-NEs were more efficient than uncoated ones for the oral delivery of RPG. Cs-RPG-NEs showed a longer t_1/2 and higher AUC_0-∞ compared to control group. The relative bioavailability of Cs-RPG-NEs was higher than that of uncoated RPG-NEs and free drug. Collectively, these findings suggest that chitosan-coated nanoemulsions are promising carrier for improving the oral bioavailability of RPG.

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

Objective:

The purpose of this systematic review and meta-analysis was to summarize the potential impact of CYP2C8 and SLCO1B1 genetic polymorphisms on repaglinide pharmacokinetics.

Methods:

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.

Results:

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.

Conclusion:

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.

Is metformin still the most efficacious first-line oral hypoglycaemic drug in treating type 2 diabetes? A network meta-analysis of randomized controlled trials

OBJECTIVES

The objective of the study is to compare the efficacy of hypoglycaemic drugs for type 2 diabetes mellitus (T2DM) by network meta-analysis of randomized controlled trials (RCTs).

METHODS

We compared 11 major oral hypoglycaemic drugs under five categories evaluated by RCTs as drug monotherapy for the patients with T2DM, measuring glycosylated haemoglobin (%) or fasting plasma glucose (mmol L^-1 ) as outcomes. RCT quality was assessed with the Cochrane risk of bias tool. Network meta-analysis estimated the mean differences and 95% credible intervals. Subgroup and sensitivity analyses were performed to determine the results robustness. The Grading of Recommendation, Assessment, Development, and Evaluation evidence strength was assessed.

RESULTS

Seventy-five RCTs including 33,830 patients were identified. Their study quality was high. Regarding glycosylated haemoglobin, top three anti-diabetics were repaglinide (mean differences -1.39 [95% credible intervals -1.75 to -1.03]), gliclazide (-1.37 [-2.04 to -0.71]) and metformin (-1.13 [-1.37 to -0.90]), against placebo. Regarding fasting plasma glucose, top three anti-diabetics were repaglinide (-2.01 [-2.75 to -0.97]), metformin (-1.72 [-2.16 to -1.27]) and glipizide (-1.57 [-2.44 to -0.64]), against placebo. There was no difference between metformin and repaglinide. Subgroup and sensitivity analyses found the results to be robust. The evidence strength was moderate to high.

CONCLUSION

This meta-analysis showed that repaglinide and metformin would be the most efficacious oral drugs for first-line monotherapy of T2DM.

Clopidogrel Pharmacokinetics in Malaysian Population Groups: The Impact of Inter-Ethnic Variability

Malaysia is a multi-ethnic society whereby the impact of pharmacogenetic differences between ethnic groups may contribute significantly to variability in clinical therapy. One of the leading causes of mortality in Malaysia is cardiovascular disease (CVD), which accounts for up to 26% of all hospital deaths annually. Clopidogrel is used as an adjunct treatment in the secondary prevention of cardiovascular events. CYP2C19 plays an integral part in the metabolism of clopidogrel to the active metabolite clopi-H4. However, CYP2C19 genetic polymorphism, prominent in Malaysians, could influence target clopi-H4 plasma concentrations for clinical efficacy. This study addresses how inter-ethnicity variability within the Malaysian population impacts the attainment of clopi-H4 target plasma concentration under different CYP2C19 polymorphisms through pharmacokinetic (PK) modelling. We illustrated a statistically significant difference (P < 0.001) in the clopi-H4 C_max between the extensive metabolisers (EM) and poor metabolisers (PM) phenotypes with either Malay or Malaysian Chinese population groups. Furthermore, the number of PM individuals with peak clopi-H4 concentrations below the minimum therapeutic level was partially recovered using a high-dose strategy (600 mg loading dose followed by a 150 mg maintenance dose), which resulted in an approximate 50% increase in subjects attaining the minimum clopi-H4 plasma concentration for a therapeutic effect.

Symptomatic Hypoglycemia Associated with Trimethoprim/Sulfamethoxazole and Repaglinide in a Diabetic Patient

Objective

To report a case of clinically significant hypoglycemia attributed to the concomitant use of trimethoprim/sulfamethoxazole (TMP/SMX) and repaglinide by a diabetic patient.

Case summary

A 76-year-old diabetic patient with impaired renal function and no history of hypoglycemia was receiving treatment with repaglinide 1 mg 3 times daily. Five days after TMP/SMX therapy was started for a urinary tract infection, the man developed symptomatic hypoglycemia. Repaglinide and TMP/SMX were stopped and intravenous d-glucose was administered to normalize glucose levels. Repaglinide, but not TMP/SMX, was reintroduced 5 days later and no other hypoglycemic episode occurred. Objective causality assessments revealed that the interaction was probable (World Health Organization-Uppsala Monitoring Centre) or possible (Horn Drug Interaction Probability Scale).

Discussion

This interaction between TMP/SMX and repaglinide was predictable according to available pharmacokinetic data in healthy subjects. Trimethoprim induced CYP2C8 inhibition, thus increasing the plasma concentration of repaglinide. This interaction is mentioned in the repaglinide product information. To our knowledge, however, no case of symptomatic hypoglycemia associated with a combination of repaglinide and trimethoprim has been described before. This discrepancy may be explained by the subtherapeutic dosage used in the pharmacokinetic study. Moreover, our patient had impaired renal function, which may have led to trimethoprim accumulation and potentiated its interaction with repaglinide. A direct lowering of blood glucose levels due to sulfamethoxazole, also potentiated by renal failure, could also be involved in triggering hypoglycemia.

Conclusions

This interaction between TMP/SMX and repaglinide may have involved inhibition of CYP2C8 by trimethoprim. Clinicians should be aware that this association may lead to symptomatic hypoglycemia, particularly in patients with renal dysfunction.

Granulated colloidal silicon dioxide-based self-microemulsifying tablets, as a versatile approach in enhancement of solubility and therapeutic potential of anti-diabetic agent: formulation design and in vitro/in vivo evaluation

The current research work was executed with an aim to explore and promote the potential of self-microemusifying drug delivery systems (SMEDDS) in the form of tablets, in order to enhance solubility and oral bioavailability of poorly aqueous soluble drug Repaglinide (RPG). RPG-loaded liquid SMEDDS were developed consisting Labrafil M 1944CS, Kolliphor EL and Propylene glycol, which were then characterized on various parameters. After characterization and optimization, liquid SMEDDS were converted into solid form by adsorbing on Aeroperl® 300 pharma and polyplasdone^TM XL. Further, selection of suitable excipients was done and mixed with prepared solidified SMEDDS powder followed by the preparation of self-microemulsifying tablets (SMET's) wet granulation-compression method. SMET's were subjected to differential scanning calorimetry (DSC) and particle X-ray diffraction (RXRD) studies, results of which indicated transformation of crystalline structure of RPG because of dispersion of RPG at molecular level in liquid SMEDDS. This was further assured by micrographs obtained from scanning electron microscope. SMET's shown more than 85% (30 min) of in vitro drug release in contrast to conventional marketed tablets (13.2%) and pure RPG drug (3.2%). Results of in vivo studies furnished that SMET's had shown marked decrease in the blood glucose level and prolonged duration of action (up to 8 h) in comparison with conventional marketed tablets and pure RPG drug. In conclusion, SMET's serves as a promising tool for successful oral delivery of poorly aqueous soluble drug(s) such as RPG.

Update on the treatment of type 2 diabetes mellitus

To achieve good metabolic control in diabetes and keep long term, a combination of changes in lifestyle and pharmacological treatment is necessary. Achieving near-normal glycated hemoglobin significantly, decreases risk of macrovascular and microvascular complications. At present there are different treatments, both oral and injectable, available for the treatment of type 2 diabetes mellitus (T2DM). Treatment algorithms designed to reduce the development or progression of the complications of diabetes emphasizes the need for good glycaemic control. The aim of this review is to perform an update on the benefits and limitations of different drugs, both current and future, for the treatment of T2DM. Initial intervention should focus on lifestyle changes. Moreover, changes in lifestyle have proven to be beneficial, but for many patients is a complication keep long term. Physicians should be familiar with the different types of existing drugs for the treatment of diabetes and select the most effective, safe and better tolerated by patients. Metformin remains the first choice of treatment for most patients. Other alternative or second-line treatment options should be individualized depending on the characteristics of each patient. This article reviews the treatments available for patients with T2DM, with an emphasis on agents introduced within the last decade.

Transporter Expression in Liver Tissue from Subjects with Alcoholic or Hepatitis C Cirrhosis Quantified by Targeted Quantitative Proteomics

Although data are available on the change of expression/activity of drug-metabolizing enzymes in liver cirrhosis patients, corresponding data on transporter protein expression are not available. Therefore, using quantitative targeted proteomics, we compared our previous data on noncirrhotic control livers (n = 36) with the protein expression of major hepatobiliary transporters, breast cancer resistance protein (BCRP), bile salt export pump (BSEP), multidrug and toxin extrusion protein 1 (MATE1), multidrug resistance-associated protein (MRP)2, MRP3, MRP4, sodium taurocholate-cotransporting polypeptide (NTCP), organic anion-transporting polypeptides (OATP)1B1, 1B3, 2B1, organic cation transporter 1 (OCT1), and P-glycoprotein (P-gp) in alcoholic (n = 27) and hepatitis C cirrhosis (n = 30) livers. Compared with control livers, the yield of membrane protein from alcoholic and hepatitis C cirrhosis livers was significantly reduced by 56 and 67%, respectively. The impact of liver cirrhosis on transporter protein expression was transporter-dependent. Generally, reduced protein expression (per gram of liver) was found in alcoholic cirrhosis livers versus control livers, with the exception that the expression of MRP3 was increased, whereas no change was observed for MATE1, MRP2, OATP2B1, and P-gp. In contrast, the impact of hepatitis C cirrhosis on protein expression of transporters (per gram of liver) was diverse, showing an increase (MATE1), decrease (BSEP, MRP2, NTCP, OATP1B3, OCT1, and P-gp), or no change (BCRP, MRP3, OATP1B1, and 2B1). The expression of hepatobiliary transporter protein differed in different diseases (alcoholic versus hepatitis C cirrhosis). Finally, incorporation of protein expression of OATP1B1 in alcoholic cirrhosis into the Simcyp physiologically based pharmacokinetics cirrhosis module improved prediction of the disposition of repaglinide in liver cirrhosis patients. These transporter expression data will be useful in the future to predict transporter-mediated drug disposition in liver cirrhosis patients.

Current Concepts in Diabetes Mellitus and Chronic Liver Disease: Clinical Outcomes, Hepatitis C Virus Association, and Therapy

Hereditary type 2 diabetes mellitus is a risk factor for chronic liver disease, and ~30 % of patients with liver cirrhosis develop diabetes. Diabetes mellitus has been associated with cirrhotic and non-cirrhotic hepatitis C virus liver infection, can aggravate the course the liver infection, and can induce a lower sustained response to antiviral treatment. Evidences that HCV may induce metabolic and autoimmune disturbances leading to hypobetalipoproteinemia, steatosis, insulin resistance, impaired glucose tolerance, thyroid disease, and gonadal dysfunction have been found. Prospective studies have demonstrated that diabetes increases the risk of liver complications and death in patients with cirrhosis. However, treatment of diabetes in these patients is complex, as antidiabetic drugs can promote hypoglycemia and lactic acidosis. There have been few therapeutic studies evaluating antidiabetic treatments in patients with liver cirrhosis published to date; thus, the optimal treatment for diabetes and the impact of treatment on morbidity and mortality are not clearly known. As numbers of patients with chronic liver disease and diabetes mellitus are increasing, largely because of the global epidemics of obesity and nonalcoholic fatty liver disease, evaluation of treatment options is becoming more important. This review discusses new concepts on hepatogenous diabetes, the diabetes mellitus–hepatitis C virus association, and clinical implications of diabetes mellitus in patients with chronic liver disease. In addition, the effectiveness and safety of old and new antidiabetic drugs, including incretin-based therapies, will be described.

Prolonged hypoglycemia after a suicidal ingestion of repaglinide with unexpected slow plasma elimination

CONTEXT

Repaglinide is a short-acting insulin secretagogue with high interindividual variability in pharmacokinetics due to genetic polymorphisms. Little is known about repaglinide overdoses, both with respect to pharmacokinetics and appropriate management. Given its short serum half-life of less than 1 h, hypoglycemic effects of repaglinide are expected to cease within a few hours post-ingestion.

CASE DETAILS

A 15-year-old girl ingested 10.5 mg of repaglinide in a suicide attempt. Few hours later, she developed a strong food craving, nausea, abdominal pain, and a headache. The lowest recorded serum glucose was 44 mg/dl (2.4 mmol/l) 14 h post-ingestion. Using liquid chromatography-mass spectrometry, we detected repaglinide serum levels of 5.3, 2.6, and 1.0 ng/ml at 14, 20, and 26 h post-ingestion, respectively.

DISCUSSION

This case illustrates that in the context of overdose, repaglinide can lead to prolonged hypoglycemia. We therefore recommend glucose monitoring and observation for 24 h in all patients who remain hypoglycemic or show symptoms of hypoglycemia for an unusually long period of time.

Quantitation of repaglinide and metabolites in mouse whole-body thin tissue sections using droplet-based liquid microjunction surface sampling-high-performance liquid chromatography-electrospray ionization tandem mass spectrometry

Herein, quantitation aspects of a fully automated autosampler/HPLC-MS/MS system applied for unattended droplet-based surface sampling of repaglinide dosed thin tissue sections with subsequent HPLC separation and mass spectrometric analysis of parent drug and various drug metabolites were studied. Major organs (brain, lung, liver, kidney and muscle) from whole-body thin tissue sections and corresponding organ homogenates prepared from repaglinide dosed mice were sampled by surface sampling and by bulk extraction, respectively, and analyzed by HPLC-MS/MS. A semi-quantitative agreement between data obtained by surface sampling and that by employing organ homogenate extraction was observed. Drug concentrations obtained by the two methods followed the same patterns for post-dose time points (0.25, 0.5, 1 and 2 h). Drug amounts determined in the specific tissues was typically higher when analyzing extracts from the organ homogenates. In addition, relative comparison of the levels of individual metabolites between the two analytical methods also revealed good semi-quantitative agreement.

The treatment of diabetes mellitus of patients with chronic liver disease

About 80% of patients with liver cirrhosis may have glucose metabolism disorders, 30% show overt diabetes mellitus (DM). Prospective studies have demonstrated that DM is associated with an increased risk of hepatic complications and death in patients with liver cirrhosis. DM might contribute to liver damage by promoting inflammation and fibrosis through an increase in mitochondrial oxidative stress mediated by adipokines. Based on the above mentioned the effective control of hyperglycemia may have a favorable impact on the evolution of these patients. However, only few therapeutic studies have evaluated the effectiveness and safety of antidiabetic drugs and the impact of the treatment of DM on morbidity and mortality in patients with liver cirrhosis. In addition, oral hypoglycemic agents and insulin may produce hypoglycemia and lactic acidosis, as most of these agents are metabolized by the liver. This review discusses the clinical implications of DM in patients with chronic liver disease. In addition the effectiveness and safety of old, but particularly the new antidiabetic drugs will be described based on pharmacokinetic studies and chronic administration to patients. Recent reports regarding the use of the SGLT2 inhibitors as well as the new incretin-based therapies such as injectable glucagon-like peptide-1 (GLP-1) receptor agonists and oral inhibitors of dipeptidylpeptidase-4 (DPP-4) will be discussed. The establishment of clear guidelines for the management of diabetes in patients with CLD is strongly required.

Ultra rapidly dissolving repaglinide nanosized crystals prepared via bottom-up and top-down approach: influence of food on pharmacokinetics behavior

The present work was undertaken with the objectives of improving the dissolution velocity, related oral bioavailability, and minimizing the fasted/fed state variability of repaglinide, a poorly water-soluble anti-diabetic active by exploring the principles of nanotechnology. Nanocrystal formulations were prepared by both top-down and bottom-up approaches. These approaches were compared in light of their ability to provide the formulation stability in terms of particle size. Soluplus® was used as a stabilizer and Kolliphor™ E-TPGS was used as an oral absorption enhancer. In vitro dissolution profiles were investigated in distilled water, fasted and fed state simulated gastric fluid, and compared with the pure repaglinide. In vivo pharmacokinetics was performed in both the fasted and fed state using Wistar rats. Oral hypoglycemic activity was also assessed in streptozotocin-induced diabetic rats. Nanocrystals TD-A and TD-B showed 19.86 and 25.67-fold increase in saturation solubility, respectively, when compared with pure repaglinide. Almost 10 (TD-A) and 15 (TD-B)-fold enhancement in the oral bioavailability of nanocrystals was observed regardless of the fasted/fed state compared to pure repaglinide. Nanocrystal formulations also demonstrated significant (p < 0.001) hypoglycemic activity with faster onset (less than 30 min) and prolonged duration (up to 8 h) compared to pure repaglinide (after 60 min; up to 4 h, respectively).

Pharmacogenomics of glinides

Glinides, including repaglinide, nateglinide and mitiglinide, are a type of fasting insulin secretagogue that could help to mimic early-phase insulin release, thus providing improved control of the postprandial glucose levels. Glinides stimulate insulin secretion by inhibiting ATP-sensitive potassium channels in the pancreatic β-cell membrane. Although glinides have been widely used clinically and display excellent safety and efficacy, the response to glinides varies among individuals, which is partially due to genetic factors involved in drug absorption, distribution, metabolism and targeting. Several pharmacogenomic studies have demonstrated that variants of genes involved in the pharmacokinetics or pharmacodynamics of glinides are associated with the drug response. Polymorphisms of genes involved in drug metabolism, such as CYP2C9, CYP2C8 and SLCO1B1, may influence the efficacy of glinides and the incidence of adverse effects. In addition, Type 2 diabetes mellitus susceptibility genes, such as KCNQ1, PAX4 and BETA2, also influence the efficacy of glinides. In this article, we review and discuss current pharmacogenomics researches on glinides, and hopefully provide useful data and proof for clinical application.

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

BACKGROUND

The aim of this study was to investigate the effects of nifedipine on the bioavailability and pharmacokinetics of repaglinide in rats.

METHODS

The 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 (0.5 mg/kg) and intravenous (0.2 mg/kg) administration of repaglinide to rats in the presence and absence of nifedipine (1 and 3 mg/kg).

RESULTS

Administration of nifedipine resulted in inhibition CYP3A4 activity with an IC50 value of 7.8 μM, 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.

CONCLUSION

Nifedipine 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.

Pharmacokinetic and toxicological considerations for the treatment of diabetes in patients with liver disease

INTRODUCTION

Patients with type 2 diabetes have an increased risk of chronic liver disease (CLD) such as non-alcoholic fatty liver disease and steatohepatitis and about one-third of cirrhotic patients have diabetes. However, the use of several antidiabetic agents may be a cause for concern in the case of hepatic impairment (HI).

AREAS COVERED

An extensive literature search was performed to analyze the influence of HI on the pharmacokinetics (PK) of glucose-lowering agents and the potential consequences for clinical practice as far as the efficacy/safety balance of their use in diabetic patients with CLD is concerned.

EXPERT OPINION

Almost no PK studies have been published regarding metformin, sulfonylureas, thiazolidinediones and α-glucosidase inhibitors in patients with HI. Only mild changes in PK of glinides, dipeptidyl peptidase-4 inhibitors and sodium glucose cotransporters type 2 inhibitors were observed in dedicated PK studies in patients with various degrees of HI, presumably without major clinical relevance although large clinical experience is lacking. Glucagon-like peptide-1 receptor agonists have a renal excretion rather than liver metabolism. Rare anecdotal case reports of hepatotoxicity have been described with various glucose-lowering agents contrasting with numerous reassuring data. Nevertheless, caution should be recommended, especially in patients with advanced cirrhosis, including with the use of metformin.

The role of nateglinide and repaglinide, derivatives of meglitinide, in the treatment of type 2 diabetes mellitus

Type 2 diabetes mellitus (T2DM) is one of the most common chronic diseases worldwide, presenting a great challenge to the public health systems due to high morbidity and mortality, because of frequent micro-/macro-vascular complications. Many treatment options are now available, with different efficacy as well as mechanisms of action to improve deranged glucose metabolism. We review some of the available data on derivatives of meglitinide, namely nateglinide and repaglinide. These two compounds increase insulin secretion by a mechanism similar to the one of sulfonylureas, but with a shorter half-life. Nateglinide and repaglinide, derivatives of meglitinides, have characteristic pharmacodynamic and pharmacokinetic properties that, together with their proposed mechanism of action, make them useful for type 2 diabetes mellitus, especially when used in combination therapy.

Overview of food products and dietary constituents with antidiabetic properties and their putative mechanisms of action: a natural approach to complement pharmacotherapy in the management of diabetes

Diabetes is one of the fastest growing chronic, noncommunicable diseases worldwide. Currently, 11 major classes of pharmacotherapy are available for the management of this metabolic disorder. However, the usage of these drugs is often associated with undesirable side effects, including weight gain and hypoglycemia. There is thus a need for new, safe and effective treatment strategies. Diet is known to play a major role in the prevention and management of diabetes. Numerous studies have reported the putative association of the consumption of specific food products, or their constituents, with the incidence of diabetes, and mounting evidence now suggests that some dietary factors can improve glycemic regulation. Foods and dietary constituents, similar to synthetic drugs, have been shown to modulate hormones, enzymes, and organ systems involved in carbohydrate metabolism. The present article reviews the major classes and modes of action of antidiabetic drugs, and examines the evidence on food products and dietary factors with antidiabetic properties as well as their plausible mechanisms of action. The findings suggest potential use of dietary constituents as a complementary approach to pharmacotherapy in the prevention and/or management of diabetes, but further research is necessary to identify the active components and evaluate their efficacy and safety.

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 AUC_0-∞ 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.

KCNQ1 gene polymorphisms are associated with the therapeutic efficacy of repaglinide in Chinese type 2 diabetic patients

The present study evaluated the effects of KCNQ1 rs2237892 and rs2237895 polymorphisms on repaglinide efficacy in Chinese patients with type 2 diabetes mellitus (T2DM). In all, 367 T2DM patients and 214 controls were genotyped. Forty of the T2DM patients were randomly selected to undergo 8 weeks repaglinide treatment. The frequency of the rs2237892 allele was lower in the T2DM patients than in the control group (P < 0.05). The frequency of the rs2237895 C allele was higher in T2DM patients than in healthy control subjects (P < 0.05). Diabetic patients with the rs2237892 risk C allele had lower fasting insulin levels (P < 0.01) and homeostasis model assessment of insulin resistance (HOMA-IR; P < 0.01) values than carriers of the T allele. Diabetic patients with the rs2237895 risk C allele had higher fasting plasma glucose (P < 0.01), postprandial plasma glucose (PPG) levels (P < 0.01) and HOMA-IR values (P < 0.01) than those with the A allele. Following repaglinide treatment, those T2DM patients with the rs2237892 T allele and rs2237895 C allele were more likely to have a positive response to repaglinide in terms of PPG levels (P < 0.05) than T2DM patients with the rs2237892 CC and rs2237895 AA genotypes. In conclusion, KCNQ1 rs2237892 and rs2237895 polymorphisms were found to be associated with the therapeutic efficacy of repaglinide in Chinese T2DM patients.

NeuroD1 A45T and PAX4 R121W polymorphisms are associated with plasma glucose level of repaglinide monotherapy in Chinese patients with type 2 diabetes

AIMS

We aimed to determine whether NeuroD1/BETA2 and PAX4 polymorphisms were associated with the therapeutic efficacy of repaglinide in Chinese type 2 diabetes mellitus (T2DM) patients.

METHODS

Three hundred and sixty-eight T2DM patients and 132 healthy control subjects were genotyped by restriction fragment length polymorphism. Forty-three patients with various genotypes were randomly selected to undergo 8 weeks of repaglinide treatment (3 mg day(-1)). Fasting plasma glucose, postprandial plasma glucose, glycated haemoglobin, fasting and postprandial serum insulin (FINS, PINS), homeostasis model assessment for insulin resistance, serum triglyceride, total cholesterol, low-density lipoprotein-cholesterol and high-density lipoprotein-cholesterol were determined before and after repaglinide treatment.

RESULTS

The allelic frequency of NeuroD1/BETA2 T45 was higher in T2DM patients than in the control subjects [13.45 vs. 6.82%, P < 0.01, odds ratios = 2.342 (1.365, 4.019), P= 0.002]. Type 2 diabetes mellitus patients with the mutated allele of NeuroD1/BETA2 A45T polymorphism showed higher FINS (13.46 ± 12.57 vs. 10.04 ± 7.09 mU l(-1) , P < 0.05) (11.67, 14.83 vs. 8.38, 11.37) and PINS (52.11 ± 40.93 vs. 68.66 ± 43.87 mU l(-1), P < 0.05) (44.89, 58.35 vs. 55.35, 88.87) than individuals with the T allele. The PAX4 R121W R allele carriers had higher PINS (52.11 ± 40.93 vs. 68.66 ± 43.87 mU l(-1), P < 0.05) (44.89, 58.35 vs. 55.35, 88.87) than subjects with the W allele. After repaglinide treatment, patients with the T allele of NeuroD1/BETA2 A45T polymorphisms had attenuated efficacy on fasting plasma glucose (-2.79 ± 2.14 vs.-0.99 ± 1.80 mmol l(-1), P < 0.01) (-3.53, -1.84 vs.-1.99, -0.13) and postprandial plasma glucose (-6.71 ± 5.90 vs.-2.54 ± 3.39 mmol l(-1), P < 0.01) (-9.28, -4.62 vs.-4.34, -0.84). Patients with the RR genotype of PAX4 R121W showed better efficacy with respect to the level of postprandial plasma glucose than R/W genotypes (-6.53 ± 6.52 vs.-2.95 ± 1.17 mmol l(-1), P < 0.05) (-8.20, -4.89 vs.-3.92, -1.20).

CONCLUSIONS

The NeuroD1/BETA2 and PAX4 polymorphisms were substantially associated with plasma glucose level after repaglinide monotherapy.

Analysis of the repaglinide concentration increase produced by gemfibrozil and itraconazole based on the inhibition of the hepatic uptake transporter and metabolic enzymes

The plasma concentration of repaglinide is reported to increase greatly when given after repeated oral administration of itraconazole and gemfibrozil. The present study analyzed this interaction based on a physiologically based pharmacokinetic (PBPK) model incorporating inhibition of the hepatic uptake transporter and metabolic enzymes involved in repaglinide disposition. Firstly, the plasma concentration profiles of inhibitors (itraconazole, gemfibrozil, and gemfibrozil glucuronide) were reproduced by a PBPK model to obtain their pharmacokinetic parameters. The plasma concentration profiles of repaglinide were then analyzed by a PBPK model, together with those of the inhibitors, assuming a competitive inhibition of CYP3A4 by itraconazole, mechanism-based inhibition of CYP2C8 by gemfibrozil glucuronide, and inhibition of organic anion transporting polypeptide (OATP) 1B1 by gemfibrozil and its glucuronide. The plasma concentration profiles of repaglinide were well reproduced by the PBPK model based on the above assumptions, and the optimized values for the inhibition constants (0.0676 nM for itraconazole against CYP3A4; 14.2 μM for gemfibrozil against OATP1B1; and 5.48 μM for gemfibrozil glucuronide against OATP1B1) and the fraction of repaglinide metabolized by CYP2C8 (0.801) were consistent with the reported values. The validity of the obtained parameters was further confirmed by sensitivity analyses and by reproducing the repaglinide concentration increase produced by concomitant gemfibrozil administration at various timings/doses. The present findings suggested that the reported concentration increase of repaglinide, suggestive of synergistic effects of the coadministered inhibitors, can be quantitatively explained by the simultaneous inhibition of the multiple clearance pathways of repaglinide.

Repaglinide: a review of its use in type 2 diabetes mellitus

Oral repaglinide (GlucoNorm®; NovoNorm®; Prandin®; Surepost®) is a rapid-acting insulin secretagogue that lowers postprandial glucose (PPG) excursions by targeting early-phase insulin release, with reductions in PPG considered to be important in reducing long-term cardiovascular complications of diabetes mellitus. Repaglinide, a carbamoylbenzoic acid derivative, is chemically related to the meglitinide class of insulin secretagogues, but unrelated to the sulfonylurea insulin secretagogues. Meglitinides, including repaglinide, have a distinct binding site at the β-cell membrane, which differs from that of sulfonylureas, and corresponds to greater insulinotropic effects with repaglinide than with glibenclamide and/or glimepiride and a more rapid onset of action in in vitro and in vivo studies. This article reviews the clinical efficacy and tolerability of oral repaglinide in the treatment of patients with type 2 diabetes and provides an overview of its pharmacological properties. In well designed clinical trials of up to 52 weeks' duration and in the clinical practice setting, recommended dosages of repaglinide (0.5-4 mg three times daily up to 30 minutes prior to a meal) provided effective glycaemic control and were generally well tolerated in treatment-naive or -experienced adult patients with type 2 diabetes, including elderly patients and those with renal impairment. Furthermore, as monotherapy or in combination with other oral antihyperglycaemic drugs, repaglinide was at least as effective as other oral antihyperglycaemic drugs at improving or maintaining glycaemic control, with a tolerability profile that was generally similar to that of sulfonylurea drugs and nateglinide. Thus, repaglinide remains an effective option for the management of patients with type 2 diabetes.

Drug interactions with oral antidiabetic agents: pharmacokinetic mechanisms and clinical implications

There is a growing epidemic of type 2 diabetes (T2DM), and it is associated with various comorbidities. Patients with T2DM are usually treated with multiple drugs, and are therefore at an increased risk of harmful drug-drug interactions (DDIs). Several potentially life-threatening DDIs concerning oral antidiabetic drugs have been identified. This has mostly been initiated by case reports but, more recently, the understanding of their mechanisms has greatly increased. In this article, we review the pharmacokinetic DDIs concerning oral antidiabetics, including metformin, sulfonylureas, meglitinide analogs, thiazolidinediones and dipeptidyl peptidase-4 inhibitors, and the underlying mechanistic basis that can help to predict and prevent DDIs. In particular, the roles of membrane transporters and cytochrome P450 (CYP) enzymes in these DDIs are discussed.

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.