The bioavailability time of commonly used thymidine analogues after intraperitoneal delivery in mice: labeling kinetics in vivo and clearance from blood serum.

Detection of synthetic thymidine analogues after their incorporation into replicating DNA during the S-phase of the cell cycle is a widely exploited methodology for evaluating proliferative activity, tracing dividing and post-mitotic cells, and determining cell-cycle parameters both in vitro and in vivo. To produce valid quantitative readouts for in vivo experiments with single intraperitoneal delivery of a particular nucleotide, it is necessary to determine the time interval during which a synthetic thymidine analogue can be incorporated into newly synthesized DNA, and the time by which the nucleotide is cleared from the blood serum. To date, using a variety of methods, only the bioavailability time of tritiated thymidine and 5-bromo-2'-deoxyuridine (BrdU) have been evaluated. Recent advances in double- and triple-S-phase labeling using 5-iodo-2'-deoxyuridine (IdU), 5-chloro-2'-deoxyuridine (CldU), and 5-ethynyl-2'-deoxyuridine (EdU) have raised the question of the bioavailability time of these modified nucleotides. Here, we examined their labeling kinetics in vivo and evaluated label clearance from blood serum after single intraperitoneal delivery to mice at doses equimolar to the saturation dose of BrdU (150 mg/kg). We found that under these conditions, all the examined thymidine analogues exhibit similar labeling kinetics and clearance rates from the blood serum. Our results indicate that all thymidine analogues delivered at the indicated doses have similar bioavailability times (approximately 1 h). Our findings are significant for the practical use of multiple S-phase labeling with any combinations of BrdU, IdU, CldU, and EdU and for obtaining valid labeling readouts.

The Effect of CYP2C9 Genotype Variants in Type 2 Diabetes on the Pharmacological Effectiveness of Sulfonylureas, Diabetic Retinopathy, and Nephropathy.

AIM: Type 2 diabetes (T2D), as a major cause of morbidity and mortality, is predicted to have a prevalence of 629 million by 2045. As diabetic patients show considerable inter-individual variation in response to antidiabetic treatment, this study aimed to investigate the gene polymorphism of cytochrome P450 as well as the effectiveness and safety of glibenclamide and gliclazide for different genotypes of CYP2C9. Besides, the chronic side effects of T2D including retinal microvasculature complications or retinopathy and renal dysfunction due to nephropathy in different genotypes were considered. PATIENTS AND METHODS: The participants including 80 T2D patients treated with glibenclamide or gliclazide were recruited from university hospitals of Ahvaz Jundishpur University of Medical Sciences, Ahvaz, in the southwest of Iran. Blood samples were collected from the patients at 2.5h after the morning dose of glibenclamide and 12h after the last dose of gliclazide. Genotyping from the extracted DNA was, then, performed using PCR-RFLP. The plasma level of glibenclamide and gliclazide was, in turn, measured by the reverse-phase high-pressure liquid chromatography. RESULTS: The results showed that the wild-type allele, i.e., CYP2C9*1, occurred in the highest frequency (0.8), while the frequency rates of the mutant allele, i.e., CYP2C9*2 and CYP2C9*3, were 0.15 and 0.05, respectively. Moreover, no significant association was found between any of the genotypes as well as the clinical and biochemical characteristics of the patients. The findings also showed that the plasma level of sulfonylureas (i.e., glibenclamide and gliclazide) was the highest in the patients with the CYP2C9*3 allele. It was also found that 75.9% of the patients with variant genotypes had experienced hypoglycemia events. Furthermore, in the absence of wild type allele, a significant increase was observed in retinopathy (p=0.039) and nephropathy (p=0.05). CONCLUSION: The findings can provide guidelines for the optimal management of the treatment protocols with sulfonylurea intended to control the T2D complications.

Binding of sulphonylureas to plasma proteins - A KATP channel perspective.

Sulphonylurea drugs stimulate insulin secretion from pancreatic ß-cells primarily by inhibiting ATP sensitive potassium (KATP) channels in the ß-cell membrane. The effective sulphonylurea concentration at its site of action is significantly attenuated by binding to serum albumin, which makes it difficult to compare in vitro and in vivo data. We therefore measured the ability of gliclazide and glibenclamide to inhibit KATP channels and stimulate insulin secretion in the presence of serum albumin. We used this data, together with estimates of free drug concentrations from binding studies, to predict the extent of sulphonylurea inhibition of KATP channels at therapeutic concentrations in vivo. KATP currents from mouse pancreatic ß-cells and Xenopus oocytes were measured using the patch-clamp technique. Gliclazide and glibenclamide binding to human plasma were determined in spiked plasma samples using an ultrafiltration-mass spectrometry approach. Bovine serum albumin (60g/l) produced a mild, non-significant reduction of gliclazide block of KATP currents in pancreatic ß-cells and Xenopus oocytes. In contrast, glibenclamide inhibition of recombinant KATP channels was dramatically suppressed by albumin (predicted free drug concentration <0.1%). Insulin secretion was also reduced. Free concentrations of gliclazide and glibenclamide in the presence of human plasma measured in binding experiments were 15% and 0.05%, respectively. Our data suggest the free concentration of glibenclamide in plasma is too low to account for the drug's therapeutic effect. In contrast, the free gliclazide concentration in plasma is high enough to close KATP channels and stimulate insulin secretion.

Effect of Tinospora cordifolia aqua-alcoholic extract on pharmacokinetic of Glibenclamide in rat: An herb-drug interaction study.

Tinospora cordifolia (TC) has been used as a complimentary/alternative medicine against diabetes. Considering its potential to modulate metabolic enzymes, Tinospora cordifolia extract (TCE) may influence the metabolism of the antidiabeic drug Glibenclamide following co-administration. Accordingly, this work was undertaken to evaluate impact of TCE on fate of Glibenclamide. Activity of clinically important Cytochrome P450 isoenzymes were inhibited in the order of CYP2C9 > CYP2D6 > CYP2C19 > CYP1A2 > CYP3A4. Formations of metabolites were inhibited with increasing concentration of TCE in both rat and human liver microsomes. TCE was co- administered in three different groups (0, 100 and 400 mg/kg) with Glibenclamide at 1 mg/kg dose to observe the alteration in pharmacokinetic parameters of Glibenclamide. The rats were pretreated with 0 (vehicle), 100 and 400 mg/kg dose of TCE b.i.d for 14 days and on the 14th day all three groups were administered with 1 mg/kg Glibenclamide. Pharmacokinetic parameters were analyzed based on plasma concentrations of Glibenclamide from all the groups by LC-HRMS methods using Glipizide as an internal standard. At 400 mg/kg dose, a marked increase in the bio availability of Glibenclamide was observed with a significant delay of Tmax and suppression of clearance.

Selective and rapid determination of tadalafil and finasteride using solid phase extraction by high performance liquid chromatography and tandem mass spectrometry.

Highly selective and fast liquid chromatography-tandem mass spectrometric (LC-MS/MS) method was developed and validated for simultaneous determination of tadalafil (TDL) and finasteride (FNS) in human plasma. The method was successfully applied for analysis of TDL and FNS samples in clinical study. The method was validated as per USFDA (United States Food and Drug Administration), EMA (European Medicines Agency), and ANVISA (Agência Nacional de Vigilância Sanitária-Brazil) bio analytical method validation guidelines. Glyburide (GLB) was used as common internal standard (ISTD) for both analytes. The selected multiple reaction monitoring (MRM) transitions for mass spectrometric analysis were m/z 390.2/268.2, m/z 373.3/305.4 and m/z 494.2/369.1 for TDL, FNS and ISTD respectively. The extraction of analytes and ISTD was accomplished by a simple solid phase extraction (SPE) procedure. Rapid analysis time was achieved on Zorbax Eclipse C18 column (50 × 4.6 mm, 5 µm). The calibration ranges for TDL and FNS were 5-800 ng/ml and 0.2-30 ng/ml respectively. The results of precision and accuracy, linearity, recovery and matrix effect of the method are acceptable. The accuracy was in the range of 92.9%-106.4% and method precision was also good; %CV was less than 8.1%.

The role of particle size of glyburide crystals in improving its oral absorption.

Currently, nanosizing is becoming increasingly prevalent as an efficient way for the improvement of oral drug absorption. This study mainly focuses on two points, namely the crystal properties, and the in vitro and in vivo characterizations of drug crystals during the nanosizing process. We used glyburide, an oral type 2 diabetes (T2D) medication, as our model drug. We sought to reduce the crystalline size of this drug and evaluate its absorption properties by comparing it with the original coarse drug because of previous reports about its gastrointestinal absorption insufficiency. Glyburide crystals, ranging from 237.6 to 4473 nm were prepared successfully by jet milling and media milling. The particle sizes and the crystal morphology were analyzed by characterization of the solid states, equilibrium solubility, and dissolution behavior. Additionally, pharmacokinetic study was performed in SD rats. The solid state results indicated a loss in crystallinity, amide-imidic acid interconversion, and partial amorphization during nanosizing. Further, in in vitro tests, nanocrystal formulations remarkably increased the solubility and dissolution of the drug (compared to microcrystals). In the in vivo test, reducing the particle size from 601.3 to 312.5 nm showed no improvement on the C max and AUC (0-36 h) values, while a profound slowing of the drug elimination occurred with reduction of particle size. Further reduction from 312.5 to 237.6 nm lead to a significant increase (p < 0.001) of the AUC (0-36 h) from 6857.8 ± 369.3 ng mL-1 h to 12,928.3 ± 1591.4 ng mL-1 h, respectively, in rats. Our present study confirmed that nanosizing has a tremendous impact on promoting the oral absorption of glyburide.

Evaluation of the pharmacokinetics of glibenclamide tablet given, off label, orally to children suffering from neonatal syndromic hyperglycemia.

PURPOSE: Glibenclamide (Gb) is used in type II diabetes mellitus but also in the last 10 years, off label, in patients with neonatal syndromic hyperglycemia carrying a mutation of Kir6.2 or SUR1. No studies have reported Gb pharmacokinetics in children. In this study, oral Gb pharmacokinetics was investigated in children in order to describe the concentration time courses, the influence of covariates, and the relationships between drug concentrations and efficacy. METHODS: Gb concentrations were measured in 18 children after the switch from subcutaneous insulin to oral tablets of Gb (crushed tablets for 33 % of patients). A total of 229 plasma Gb concentrations and 187 blood glucose measurements were available. A population model was developed with NONMEM. RESULTS: Body weight was the most significant parameter on clearance and explained a substantial part of the variability. A variant genotype of CYP2C9 (i.e., *1/*2 and *1/*3) explained also a part of the remaining variability on Gb clearance. Patients carrying these allelic variants had a clearance decreased by 45 %. A link between daily area under the curve (AUC0-24 h) and metabolic control diabetes was found. CONCLUSIONS: This study evaluates for the first time the pharmacokinetics of oral Gb in children and constitutes a first step towards dose individualization of this drug in a particularly vulnerable population.

Paroxetine decreased plasma exposure of glyburide partly via inhibiting intestinal absorption in rats.

Accumulating evidences have shown that diabetes is often accompanied with depression, thus it is possible that oral antidiabetic agent glyburide and antidepressive agent paroxetine are co-administered in diabetic patients. The aim of this study was to assess interactions between glyburide and paroxetine in rats. Effect of paroxetine on pharmacokinetics of orally administered glyburide was investigated. Effect of naringin (NAR), an inhibitor of rat intestinal organic anion transporting polypeptides 1a5 (Oatp1a5), on pharmacokinetics of glyburide was also studied. The results showed that co-administration of paroxetine markedly reduced plasma exposure and prolonged Tmax of glyburide, accompanied by significant increase in fecal excretion of glyburide. Co-administration of naringin also significantly decreased plasma exposure of glyburide. Data from intestinal perfusion experiments showed that both paroxetine and naringin significantly inhibited intestinal absorption of glyburide. Caco-2 cells were used to investigate whether paroxetine and naringin affected intestinal transport of glyburide and fexofenadine (a substrate of Oatp1a5). The results showed that both paroxetine and naringin greatly inhibited absorption of glyburide and fexofenadine. All results gave a conclusion that co-administration of paroxetine decreased plasma exposure of glyburide in rats via inhibiting intestinal absorption of glyburide, which may partly be attributed to the inhibition of intestinal Oatp1a5 activity.

Glyburide transport across the human placenta.

OBJECTIVE: To estimate the magnitude of transplacental transfer of glyburide in women with gestational diabetes mellitus (GDM). METHODS: A prospective, observational study was conducted on women with GDM on glyburide therapy. On delivery admission, the glyburide dose and time of last dose were recorded. Immediately postdelivery, maternal and umbilical venous blood samples were obtained and the concentrations of glyburide were determined by high-performance liquid chromatography-mass spectrometry with a limit of detection of 0.25 ng/mL. RESULTS: Nineteen patient dyads were analyzed. The mean total daily maternal glyburide dose was 6.6±6.3 mg per day and the mean time between last dose and sampling was 13.3±6.5 hours. The mean maternal serum glyburide level at birth was 15.4±20.8 ng/mL, whereas the mean umbilical glyburide level was 7.5±8.2 ng/mL, which showed a statistical correlation (r=0.72, P<.01). There were statistically significant relationships between total maternal glyburide dose (1.25-20 mg per day) and maternal glyburide levels (0.93-70.71 ng/mL; r=0.46, P≤.01) and between total maternal glyburide dose and umbilical glyburide levels (0.95-32.41 ng/mL; r=0.43, P≤.01) However, we observed wide variability in maternal and umbilical glyburide levels at both extremes of the total glyburide dose. Seventy-nine percent of cord samples (15/19) had glyburide levels less than 10 ng/mL (the limit of detection reported in earlier studies) and 37% (7/19) were higher than the corresponding maternal samples. CONCLUSION: Transplacental transfer of glyburide is highly variable among patients, corroborating ex vivo placental perfusion studies showing a transport-mediated glyburide efflux from the fetal to the maternal circulation. In most neonates (79%), glyburide levels were below 10 ng/mL. LEVEL OF EVIDENCE: III.

Quantitative determination of metformin, glyburide and its metabolites in plasma and urine of pregnant patients by LC-MS/MS.

This report describes the development and validation of an LC-MS/MS method for the quantitative determination of glyburide (GLB), its five metabolites (M1, M2a, M2b, M3 and M4) and metformin (MET) in plasma and urine of pregnant patients under treatment with a combination of the two medications. The extraction recovery of the analytes from plasma samples was 87-99%, and that from urine samples was 85-95%. The differences in retention times among the analytes and the wide range of the concentrations of the medications and their metabolites in plasma and urine patient samples required the development of three LC methods. The lower limit of quantitation (LLOQ) of the analytes in plasma samples was as follows: GLB, 1.02 ng/mL; its five metabolites, 0.100-0.113 ng/mL; and MET, 4.95 ng/mL. The LLOQ in urine samples was 0.0594 ng/mL for GLB, 0.984-1.02 ng/mL for its five metabolites and 30.0 µg/mL for MET. The relative deviation of this method was <14% for intra-day and inter-day assays in plasma and urine samples, and the accuracy was 86-114% in plasma, and 94-105% in urine. The method described in this report was successfully utilized for determining the concentrations of the two medications in patient plasma and urine.

Effect of canagliflozin on the pharmacokinetics of glyburide, metformin, and simvastatin in healthy participants.

Drug-drug interactions between canagliflozin, a sodium glucose co-transporter 2 inhibitor, and glyburide, metformin, and simvastatin were evaluated in three phase-1 studies in healthy participants. In these open-label, fixed sequence studies, participants received: Study 1-glyburide 1.25 mg/day (Day 1), canagliflozin 200 mg/day (Days 4-8), canagliflozin with glyburide (Day 9); Study 2-metformin 2,000 mg/day (Day 1), canagliflozin 300 mg/day (Days 4-7), metformin with canagliflozin (Day 8); Study 3-simvastatin 40 mg/day (Day 1), canagliflozin 300 mg/day (Days 2-6), simvastatin with canagliflozin (Day 7). Pharmacokinetic parameters were assessed at prespecified intervals. Co-administration of canagliflozin and glyburide did not affect the overall exposure (maximum plasma concentration [Cmax ] and area under the plasma concentration-time curve [AUC]) of glyburide and its metabolites (4-trans-hydroxy-glyburide and 3-cis-hydroxy-glyburide). Canagliflozin did not affect the peak concentration of metformin; however, AUC increased by 20%. Though Cmax and AUC were slightly increased for simvastatin (9% and 12%) and simvastatin acid (26% and 18%) following coadministration with canagliflozin, compared with simvastatin administration alone; however, no effect on active 3-hydroxy-3-methyl-glutaryl-CoA (HMG-CoA) reductase inhibitory activity was observed. There were no serious adverse events or hypoglycemic episodes. No drug-drug interactions were observed between canagliflozin and glyburide, metformin, or simvastatin. All treatments were well-tolerated in healthy participants.

A pharmacologic approach to the use of glyburide in pregnancy.

Despite widespread use of glyburide to treat pregnancy-related hyperglycemia, the dosing regimen is based in large part on pharmacokinetic and pharmacodynamic studies in men and nonpregnant women. Like many medications used by pregnant women, adequate pharmacokinetic and pharmacodynamic data in pregnancy have been sorely lacking. This lack of information can lead to both overdosing with excessive side effects and underdosing with an inadequate therapeutic response. Both of these problems may apply to glyburide use in pregnancy. This commentary provides a pharmacologic basis for altering the glyburide administration regimen. Taking glyburide 1 hour before a meal may improve efficacy in patients with pregnancy-related hyperglycemia.

Review: Glycation of human serum albumin.

Glycation involves the non-enzymatic addition of reducing sugars and/or their reactive degradation products to amine groups on proteins. This process is promoted by the presence of elevated blood glucose concentrations in diabetes and occurs with various proteins that include human serum albumin (HSA). This review examines work that has been conducted in the study and analysis of glycated HSA. The general structure and properties of HSA are discussed, along with the reactions that can lead to modification of this protein during glycation. The use of glycated HSA as a short-to-intermediate term marker for glycemic control in diabetes is examined, and approaches that have been utilized for measuring glycated HSA are summarized. Structural studies of glycated HSA are reviewed, as acquired for both in vivo and in vitro glycated HSA, along with data that have been obtained on the rate and thermodynamics of HSA glycation. In addition, this review considers various studies that have investigated the effects of glycation on the binding of HSA with drugs, fatty acids and other solutes and the potential clinical significance of these effects.

The influence on DNA damage of glycaemic parameters, oral antidiabetic drugs and polymorphisms of genes involved in the DNA repair system.

The hyperglycaemia seen in type 2 diabetes mellitus (DM2) is associated with increased oxidative stress and production of reactive oxygen species, both of which are factors that can provoke DNA damage. Notwithstanding, other factors, including medications and individual susceptibility, can also induce this type of DNA lesion. The objective of this study was, therefore, to investigate the influence of glycaemic control, oral antidiabetic drugs (metformin and glibenclamide) and polymorphisms of the XRCC1 and XRCC3 genes on the frequency of DNA damage in DM2 patients, which was accessed by the cytokinesis-block micronucleus cytome and the comet assays on the ex vivo mitogenically stimulated lymphocytes. The 53 people recruited to take part in the study were already on treatment with metformin and were followed for 5 months. Ten of these patients were put on combined treatment with the addition of glibenclamide. It was observed that the greater the plasma metformin concentration, the lower the frequency of micronuclei (MN) in the sample total (P = 0.009) and also that the subset of patients using combined treatment including glibenclamide had a significantly higher MN rate 90 days after starting combined treatment (P = 0.024). In the subset who only took metformin, the rate of MN was significantly higher among carriers of the 399Gln allele on the XRCC1 gene (P = 0.008). In addition, homozygotes for the 241Thr allele exhibited a significant increase in MN in the combined treatment group (P = 0.008). Our results suggest that different combinations of oral antidiabetic drugs and polymorphisms on genes involved in the DNA damage repair system could influence the frequency of this type of chromosome lesion, which can be a useful biomarker for assessing the risk of developing cancer.

Semi-mechanistic physiologically-based pharmacokinetic modeling of clinical glibenclamide pharmacokinetics and drug-drug-interactions.

We studied if the clinical pharmacokinetics and drug-drug interactions (DDIs) of the sulfonylurea-derivative glibenclamide can be simulated via a physiologically-based pharmacokinetic modeling approach. To this end, a glibenclamide PBPK-model was build in Simcyp using in vitro physicochemical and biotransformation data of the drug, and was subsequently optimized using plasma disappearance data observed after i.v. administration. The model was validated against data observed after glibenclamide oral dosing, including DDIs. We found that glibenclamide pharmacokinetics could be adequately modeled if next to CYP metabolism an active hepatic uptake process was assumed. This hepatic uptake process was subsequently included in the model in a non-mechanistic manner. After an oral dose of 0.875 mg predicted Cmax and AUC were 39.7 (95% CI:37.0-42.7)ng/mL and 108 (95% CI: 96.9-120)ng/mLh, respectively, which is in line with observed values of 43.6 (95% CI: 37.7-49.5)ng/mL and 133 (95% CI: 107-159)ng/mLh. For a 1.75 mg oral dose, the predicted and observed values were 82.5 (95% CI:76.6-88.9)ng/mL vs 91.1 (95% CI: 67.9-115.9) for Cmax and 224 (95% CI: 202-248) vs 324 (95% CI: 197-451)ng/mLh for AUC, respectively. The model correctly predicted a decrease in exposure after rifampicin pre-treatment. An increase in glibenclamide exposure after clarithromycin co-treatment was predicted, but the magnitude of the effect was underestimated because part of this DDI is the result of an interaction at the transporter level. Finally, the effects of glibenclamide and fluconazol co-administration were simulated. Our simulations indicated that co-administration of this potent CYP450 inhibitor will profoundly increase glibenclamide exposure, which is in line with clinical observations linking the glibenclamide-fluconazol combination to an increased risk of hypoglycemia. In conclusion, glibenclamide pharmacokinetics and its CYP-mediated DDIs can be simulated via PBPK-modeling. In addition, our data underline the relevance of modeling transporters on a full mechanistic level to further improve pharmacokinetic and DDI predictions of this sulfonylurea-derivative.

Determination of glibenclamide and puerarin in rat plasma by UPLC-MS/MS: application to their pharmacokinetic interaction study.

In the treatment of diabetes mellitus, glibenclamide and puerarin may be co-administered unwittingly or wittingly. An ultra performance liquid chromatography-tandem mass spectrometry method was developed to determine the concentrations of glibenclamide and puerarin in rat plasma for the study of pharmacokinetic interaction between them. Analytes were extracted using liquid-liquid extraction. The separation was achieved on a Waters BEH C18 column using 5 mmol/L ammonium acetate solution (containing 0.1% formic acid) and methanol as mobile phase with a linear gradient program. Electrospray ionization source was applied and operated in the multiple reaction monitoring positive mode. The proposed method was proved simple, specific and reliable. Glibenclamide, Pueraria lobata extract and glibenclamide in combination with P. lobata extract were orally administered to rats, respectively. Pharmacokinetic parameters were estimated by Microsoft Excel software and analyzed by SPSS 12.0 software. Compared with glibenclamide group, pharmacokinetic parameters of glibenclamide in the co-administration group such as area under the curve and mean residence time were increased while clearance was decreased. Pharmacokinetic parameters of puerarin in the co-administration group such as peak concentration and area under the curve were enlarged while clearance and apparent volume of distribution were reduced compared with P. lobata extract group. These changes could enhance drug efficacy, but could also make drug accumulation to increase adverse effects, so it was suggested that the dosage should be adjusted or the drug concentration in plasma should be monitored if glibenclamide and puerarin were co-administered.

Effects of HuangKui capsules on glibenclamide pharmacokinetics in rats.

ETHNOPHARMACOLOGY: The main components of HuangKui capsules' are the total flavonoids extracted from the flowers of Abelmoschus manihot L medic. They have been widely used to treat chronic glomerulonephritis, diabetic nephropathy and nephrotic syndrome. The combination of HuangKui capsules and glibenclamide is a possible therapy for patients with diabetes mellitus and diabetic nephropathy. However, there is no report about effects of HuangKui capsules on the glibenclamide pharmacokinetics till now. AIM OF THE STUDY: This study was aimed investigating the effect of HuangKui capsules on pharmacokinetics of glibenclamide in rats. MATERIAL AND METHODS: Eight rats were administered with an oral dose of HuangKui capsules (0.75gkg(-1)) once daily for 10 consecutive days. All the rats were administered orally with the glibenclamide (1mgkg(-1)) before the first time and after the last time given HuangKui capsules. LC-MS/MS was utilized to determine the concentration of glibenclamide in rat plasma and to calculate the corresponding pharmacokinetic parameters. The statistical differences of the two cycles were evaluated by paired-samples t-test. RESULTS: In the rats treated with HuangKui capsules and glibenclamide, the t(1/2), the time point of maximum plasma concentration (T(max)) of glibenclamide increased obviously (p<0.05) compared with the glibenclamide alone, while maximum plasma concentrations (C(max)), area under the plasma concentration-time curve (AUC((0-t))) decreased significantly (p<0.05). There was no significant difference between other parameters. CONCLUSION: HuangKui capsules can reduce the absorption of glibenclamide and accelerate the metabolism of glibenclamide.

Influence of CYP2C9 gene polymorphisms on response to glibenclamide in type 2 diabetes mellitus patients.

PURPOSE: The antidiabetic drug glibenclamide is metabolized by the enzyme cytochrome P450 2C9 (CYP2C9) encoded by the polymorphic gene CYP2C9. Previous studies involving healthy volunteers have shown a significant influence of variant CYP2C9 genotypes on glibenclamide metabolism. The aim of this study was to investigate the influence of genetic polymorphisms of CYP2C9 on the response to glibenclamide and on glibenclamide plasma levels in type 2 diabetes mellitus patients. METHODS: The study cohort consisted of type 2 diabetes mellitus patients (n = 80) on regular therapy with glibenclamide either alone or with concomitant metformin. Plasma levels of glibenclamide were estimated by reverse phase high pressure liquid chromatography. The variant alleles of CYP2C9, namely CYP2C9 *2 and *3, were identified by PCR-restricted fragment length polymorphism. The plasma levels of glibenclamide and occurrences of hypoglycemic adverse effects with their severity were compared between the genotype groups. RESULTS: Of the 80 patients (61 males, 19 females), 78 were on concomitant treatment with two drugs, namely, glibenclamide and metformin, and two were on monotherapy with glibenclamide. There was a significant association (p < 0.001) between genotype status of CYP2C9 and the control of diabetes in patients receiving treatment with glibenclamide. There were no statistically significant differences in hypoglycemic adverse effects between the genotype groups. CONCLUSION: The type 2 diabetes mellitus patients participating in this study with variant genotypes of CYP2C9 were found to respond better to treatment with glibenclamide than those with the normal genotype. The variant genotype CYP2C9 *1/*3 did not significantly influence the hypoglycemic adverse effects among those patients on long-term glibenclamide treatment.

Impact of hyperlipidemia on plasma protein binding and hepatic drug transporter and metabolic enzyme regulation in a rat model of gestational diabetes.

It is currently unknown whether gestational diabetes mellitus (GDM), a prevalent obstetrical complication, compounds the changes in drug disposition that occur naturally in pregnancy. Hyperlipidemia occurs in GDM. Using a rat model of GDM, we determined whether excess lipids compete with drugs for plasma protein binding. Because lipids activate nuclear receptors that regulate drug transporters and metabolic enzymes, we used proteome analysis to determine whether hyperlipidemia indirectly leads to the dysregulation of these proteins in the liver. GDM was induced on gestational day 6 (GD6) via streptozotocin injection. Controls received either vehicle alone or streptozotocin with subsequent insulin treatment. Liver and plasma were collected on GD20. Glyburide and saquinavir protein binding was determined by ultrafiltration, and an established solvent method was used for plasma delipidation. Proteomics analysis was performed by using isobaric tags for relative and absolute quantitation methodology with membrane-enriched hepatic protein samples. Relative to controls, GDM rat plasma contained more cholesterol and triglycerides. Plasma protein binding of glyburide and saquinavir was decreased in GDM. Delipidation normalized protein binding in GDM plasma. Proteins linked to lipid metabolism were strongly affected in the GDM proteomics data set, with prohyperlipidemic and antihyperlipidemic changes observed, and formed networks that implicated several nuclear receptors. Up-regulation of drug transporters and metabolic enzymes was observed (e.g., multidrug resistance 1/2, CYP2A1, CYP2B9, and CYP2D3). In this study, GDM-induced hyperlipidemia decreased protein binding and was associated with drug transporter and metabolic enzyme up-regulation in the liver. Both of these findings could change drug disposition in affected pregnancies, compounding changes associated with pregnancy itself.