Pharmacogenomic analysis of ATP-sensitive potassium channels coexpressing the common type 2 diabetes risk variants E23K and S1369A.

OBJECTIVES: The common ATP-sensitive potassium (KATP) channel variants E23K and S1369A, found in the KCNJ11 and ABCC8 genes, respectively, form a haplotype that is associated with an increased risk for type 2 diabetes. Our previous studies showed that KATP channel inhibition by the A-site sulfonylurea gliclazide was increased in the K23/A1369 haplotype. Therefore, we studied the pharmacogenomics of seven clinically used sulfonylureas and glinides to determine their structure-activity relationships in KATP channels containing either the E23/S1369 nonrisk or K23/A1369 risk haplotypes. RESEARCH DESIGN AND METHODS: The patch-clamp technique was used to determine sulfonylurea and glinide inhibition of recombinant human KATP channels containing either the E23/S1369 or the K23/A1369 haplotype. RESULTS: KATP channels containing the K23/A1369 risk haplotype were significantly less sensitive to inhibition by tolbutamide, chlorpropamide, and glimepiride (IC50 values for K23/A1369 vs. E23/S1369=1.15 vs. 0.71 µmol/l; 4.19 vs. 3.04 µmol/l; 4.38 vs. 2.41 nmol/l, respectively). In contrast, KATP channels containing the K23/A1369 haplotype were significantly more sensitive to inhibition by mitiglinide (IC50=9.73 vs. 28.19 nmol/l for K23/A1369 vs. E23/S1369) and gliclazide. Nateglinide, glipizide, and glibenclamide showed similar inhibitory profiles in KATP channels containing either haplotype. CONCLUSION: Our results demonstrate that the ring-fused pyrrole moiety in several A-site drugs likely underlies the observed inhibitory potency of these drugs on KATP channels containing the K23/A1369 risk haplotype. It may therefore be possible to tailor existing therapy or design novel drugs that display an increased efficacy in type 2 diabetes patients homozygous for these common KATP channel haplotypes.

Crystallization and polymorphic transitions of chlorpropamide in aqueous 2-hydroxybutyl-beta-cyclodextrin solution.

Effects of cyclodextrins on crystallization of chlorpropamide and the polymorphic transition mechanism of the drug in aqueous solution were investigated. In the presence of 2-hydroxybutyl-beta-cyclodextrin, chlorpropamide was exclusively crystallized to metastable Form II and III polymorphs, whereas it was crystallized to stable Form A in the absence of the beta-cyclodextrin at 4 degrees C. The crystallization to metastable Form II or III polymorph was dependent upon 2-hydroxybutyl-beta-cyclodextrin concentrations employed, i.e. crystallization to Form III at a lower concentration (0.5 mM), whereas to Form II in a higher concentration (5 mM). At an intermediate concentration (2 mM), the least stable Form II crystal was initially precipitated, but it was transformed to Form III crystal. At higher temperature, Form III crystal was converted to stable Form A crystal. In aqueous solution, chlorpropamide crystallized to stable Form A crystal consecutively through metastable Forms II and III, according to "Ostwald's Rule of Stages". 2-Hydroxybutyl-beta-cyclodextrin inhibits the transition of Form II to Form III at higher concentrations and that of Form III to Form A at lower concentrations. The results suggest that 2-hydroxybutyl-beta-cyclodextrin is useful for selective preparation of metastable chlorpropamide polymorphs occurring during crystallization according to the Ostwald's rule.

The influence of lamivudine, stavudine and nevirapine on the pharmacokinetics of chlorpropamide in human subjects.

Diabetic patients tend to be prone to infections, and multiple drug therapy cannot be ruled out in the management of diabetes. The effect of three routinely prescribed antiretroviral (ARV) drugs on the pharmacokinetic profile of an antidiabetic drug, chlorpropamide, was investigated in 18 human subjects, who had recently been diagnosed positive for human immunodeficiency virus (HIV) infection. The volunteers, aged 22-44 years and weighing 59-66 kg, were randomized into three groups with six subjects in each group. The study was carried out in two phases; in the first phase, all the subjects received chlorpropamide (250 mg) in a fasting state. In the second phase, the subjects received 250 mg of chlorpropamide together with lamivudine (150 mg) or stavudine (40 mg) or nevirapine (200 mg) in a fasting state. Chlorpropamide concentrations in the plasma were determined using a high performance liquid chromatography (HPLC) method developed earlier in our laboratory, while plasma glucose levels were determined using the standard glucose oxidase method. Lamivudine and stavudine decreased significantly (P < 0.05) the mean maximum plasma concentrations (Cmax) and the area under the plasma concentration-time curve (AUC(0-168h)) of chlorpropamide, while both drugs significantly increased the absorption half-life (t(1/2ab)) and elimination half-life (t(1/2el). the apparent volume of distribution (Vd) and the plasma clearance rate (Cl) of chlorpropamide (P < 0.05). The plasma glucose levels were also significantly increased between 0.5 - 4 h post dose (P < 0.05). However, it was found that the pharmacokinetic parameters of chlorpropamide and the blood glucose levels were not significantly altered by the co-administration with nevirapine.

Effect of Nigerian meals on the pharmacokinetics of chlorpropamide in type II diabetic patients.

Food-drug interactions are best evaluated on an individual drug basis, in a group of subjects in a population at risk. This is due to their complex nature, which is a function of type and size of meal, the physical and chemical form of the drug and the time lapse between food intake and drug administration. This work was aimed at investigating the effect of three different Nigerian meals, which are regularly consumed by the three major tribes in Nigeria, on the pharmacokinetics of chlorpropamide, a drug commonly used to treat Type II diabetes in this country. Meal A (maize flour meal) was composed of 81% carbohydrate, 3% protein and 11% fat; meal B (cassava flour meal) was composed of 76% carbohydrate, 3% protein and 15% fat; while meal C (browned yam flour meal) was composed of 85% carbohydrate, 2% protein and 8% fat. The effects of the three meals were investigated by administering each of the meals alone, without the medicinal drug (Treatment I); in Treatment II each meal was administered 30 min following the administration of 250 mg chlorpropamide; in Treatment III the drug was administered together with each of the standard meals. Analysis of the plasma levels of chlorpropamide was performed by high performance liquid chromatography (HPLC). Ingestion of the meal alone (Treatment I) resulted in a significant difference in postprandial plasma glucose levels. The time to maximum plasma chlorpropamide concentration was significantly increased in Treatment III (P < 0.05), while all pharmacokinetic parameters and plasma glucose levels were not significantly altered in Treatment II. Analysis of the results demonstrated a better glycaemic response with meals A and C compared with meal B.

Avaliação de bentonita sódica purificada e bentonita sódica intercalada como promotores de dissolução de clorpropamida em comprimidos preparados por granulação úmida e compressão direta / Evaluation of purified sodium bentonite and intercalated sodium bentonite as dissolution enhancers for chlorpropamide in tablets produced by wet granulation and direct compression

O presente estudo avaliou sistemas baseados em bentonita sódica purificada e bentonita sódica purificada intercalada com colina como promotores de dissolução de clorpropamida. A intercalação da bentonita sódica foi avaliada por difração de raios X, análise termo gravimétrica, análise calorimétricade varredura e espectrometria no infravermelho. Prepararam-se misturas físicas, empastamentos (kneadings) e granulados e comprimidos, por granulação úmida e compressão direta; ambos os sistemas (físicos e comprimidos) com diversas relações fármaco: promotores de dissolução. Todos os sistemas físicos e os comprimidos foram avaliados quanto à dissolução do fármaco segundo metodologia descrita na Farmacopéia Norte-Americana (USP). Os comprimidos ainda foram avaliados quanto à dureza e friabilidade. O empastamento hidroalcoólico mostrou ser o melhor sistema físico para aumento da dissolução, entretanto é inviável para produção industrial de comprimidos. Os comprimidos de clorpropamida preparados por granulação úmida com proporção de fármaco e promotores de dissolução de 1:0,25 p/p apresentaram melhores resultados no teste de dissolução em relação aos comprimidos sem os promotores. Não houve diferença significativa entre a liberação de clorpropamida com a bentonita sódica e bentonita sódica intercalada. Os comprimidos preparados por compressão direta apresentaram, comparativamente, o melhor desempenho no teste de dissolução. Não foi evidenciado perda de cristalinidade do fármaconos sistemas estudados. O poder de desintegração da bentonita e a possível interação molecular entre o fármaco e a bentonita são as prováveis causas do aumento da dissolução da clorpropamida com tais sistemas baseados em bentonita.

Comparative bioavailability study with two chlorpropamide tablet formulations in healthy volunteers.

OBJECTIVE: The aim of this study was the assessment of the bioequivalence of two formulations (250 mg tablet) of chlorpropamide (CAS 94-20-2) in 36 healthy volunteers of both sexes. METHODS: The study was conducted using an open, randomized, two-period crossover design with a 3-week washout interval. Plasma samples were obtained over a 72-h period. Plasma chlorpropamide concentrations were analyzed by liquid chromatography coupled to tandem mass spectrometry (LC-MS-MS) with positive ion electrospray ionization using multiple reaction monitoring (MRM). From the chlorpropamide plasma concentration vs time curves, the following pharmacokinetic parameters were obtained: AUC(0-72h), AUC(inf) and C(max). RESULTS: The limit of quantification was 0.1 microg/mL for plasma chlorpropamide analysis. The geometric mean and respective 90 % confidence interval (CI) of Test/ Reference percent ratios were 93.99% (87.11%-101.41%) for C(max), 92.45% (85.96%-99.44%) for AUC(0-72h) and 90.30% (83.35%-97.82%) for AUC(0-inf). CONCLUSION: Since the 90 % CI for AUC(0-72h), AUC(0-inf) and C(max) ratios were within the 80-125%interval proposed by the US FDA, it was concluded that chlorpropamide 250 mg tablet (test formulation) was bioequivalent to the reference 250 mg tablet for of both the rate and extent of absorption.

Chlorpropamide 2-hydroxylation is catalysed by CYP2C9 and CYP2C19 in vitro: chlorpropamide disposition is influenced by CYP2C9, but not by CYP2C19 genetic polymorphism.

AIMS: We evaluated the involvement of cytochrome P450 (CYP) isoforms 2C9 and 2C19 in chlorpropamide 2-hydroxylation in vitro and in chlorpropamide disposition in vivo. METHODS: To identify CYP isoforms(s) that catalyse 2-hydroxylation of chlorpropamide, the incubation studies were conducted using human liver microsomes and recombinant CYP isoforms. To evaluate whether genetic polymorphisms of CYP2C9 and/or CYP2C19 influence the disposition of chlorpropamide, a single oral dose of 250 mg chlorpropamide was administered to 21 healthy subjects pregenotyped for CYP2C9 and CYP2C19. RESULTS: In human liver microsomal incubation studies, the formation of 2-hydroxychlorpropamide (2-OH-chlorpropamide), a major chlorpropamide metabolite in human, has been best described by a one-enzyme model with estimated K(m) and V(max) of 121.7 +/- 19.9 microm and 16.1 +/- 5.0 pmol min(-1) mg(-1) protein, respectively. In incubation studies using human recombinant CYP isoforms, however, 2-OH-chlorpropamide was formed by both CYP2C9 and CYP2C19 with similar intrinsic clearances (CYP2C9 vs. CYP2C19: 0.26 vs. 0.22 microl min(-1) nmol(-1) protein). Formation of 2-OH-chlorpropamide in human liver microsomes was significantly inhibited by sulfaphenazole, but not by S-mephenytoin, ketoconazole, quinidine, or furafylline. In in vivo clinical trials, eight subjects with the CYP2C9*1/*3 genotype exhibited significantly lower nonrenal clearance [*1/*3 vs.*1/*1: 1.8 +/- 0.2 vs. 2.4 +/- 0.1 ml h(-1) kg(-1), P < 0.05; 95% confidence interval (CI) on the difference 0.2, 1.0] and higher metabolic ratios (of chlorpropamide/2-OH-chlorpropamide in urine: *1/*3 vs.*1/*1: 1.01 +/- 0.19 vs. 0.56 +/- 0.08, P < 0.05; 95% CI on the difference - 0.9, - 0.1) than did 13 subjects with CYP2C9*1/*1 genotype. In contrast, no differences in chlorpropamide pharmacokinetics were observed for subjects with the CYP2C19 extensive metabolizer vs. poor metabolizer genotypes. CONCLUSIONS: These results suggest that chlorpropamide disposition is principally determined by CYP2C9 activity in vivo, although both CYP2C9 and CYP2C19 have a catalysing activity of chlorpropamide 2-hydroxylation pathway.

[Trial for transdermal administration of sulfonylureas].

Sulfonylureas are widely used as oral hypoglycemic drugs in the treatment of non insulin dependent diabetes mellitus (NIDDM). Since sulfonylureas are usually taken for a long period, the compliance of the patients is very important. Therefore, for the improvement of the compliance of the patients, the development of a transdermal dosage form of sulfonylureas was attempted in this study. Glibenclamide (GLI) or chlorpropamide (CHL) was chosen as a principal agent and ointments were prepared by mixing 5% of GLI or CHL with a FAPG ointment base. Penetration and shearing stresses of the ointments were determined as physical characteristics of the ointments. There was no obvious difference of characteristics between the GLI ointment, or the CHL ointment and the FAPG ointment base. In drug release tests, the CHL ointment showed better release of the drug than the GLI ointment. In both ointments, comparatively rapid release of drug was observed in the initial 1 h, and continuous slow release was observed thereafter. When the ointments were applied on the back of male Wistar rats and the plasma glucose level was measured, both CHL and GLI ointments gave lower blood glucose levels than the control (FAPG base). At the all measuring points, the GLI ointment brought about significantly lower blood glucose levels than the control (p < 0.01). Thus, it was demonstrated that sulfonylureas were absorbed through the skin and lowered the blood glucose levels. The results suggest the possibility of transdermal administration of sulfonylureas for the treatment of NIDDM.

Comparative placental transport of oral hypoglycemic agents in humans: a model of human placental drug transfer.

OBJECTIVE: This study compares the human placental transport of glyburide, glipizide, chlorpropamide, and tolbutamide. STUDY DESIGN: The recirculating single cotyledon human placenta model tested maternal-to-fetal transport in term placentas perfused immediately after delivery. Drug levels were measured by high-performance liquid chromatography and liquid scintillation spectrometry, and transport rates were calculated by comparing maternal and fetal concentrations. RESULTS: The transport of these substances differed significantly over a tenfold range (analysis of variance, p < 0.0008). A significant association exists by multiple linear regression between drug transfer and molecular weight, dissociation constant, and the octanol-water partition coefficient (R2 = 0.91, p < 0.0001). CONCLUSIONS: There is significant variability in human placental transfer rates of the oral hypoglycemics, which strongly correlates with molecular properties. These data suggest that less fetal exposure may occur with second-generation sulfonylureas and anticipate that regression models may be useful in selecting agents that minimize placental transport to the fetus.

Effect of magnesium hydroxide on the absorption and efficacy of tolbutamide and chlorpropamide.

The effect of magnesium hydroxide on the absorption and efficacy of tolbutamide and chlorpropamide was examined in a total of 32 healthy volunteers in two separate, randomized parallel-group studies, with 16 subjects in each study. After an overnight fast, the first group of 8 volunteers ingested 500 mg tolbutamide or 250 mg chlorpropamide with 150 ml water, and the second group the same doses of the active drugs with 150 ml water containing 850 mg magnesium hydroxide. Magnesium hydroxide increased the area under the plasma tolbutamide concentration-time curve (AUC) from 0 to 1 h and from 0 to 2 h by 5-fold and 2.5-fold, respectively. The peak plasma concentration, peak time and total AUC were not significantly altered. The incremental insulin area and the decremental glucose area from 0 to 1.5 h were significantly larger in the magnesium hydroxide group than in the controls. The maximum insulin response to tolbutamide was increased fourfold by coadministration of magnesium hydroxide, and it occurred about 1 h earlier than in the control group. In addition, the maximum fall in plasma glucose concentration was attained about 1 h earlier in the antacid group. A tendency to an increased rate of chlorpropamide absorption was observed after magnesium hydroxide, but it did not appear to affect the insulin and glucose responses to chlorpropamide. It is concluded that magnesium hydroxide increased the early bioavailability of tolbutamide, resulting in enhanced insulin and glucose responses. A tendency toward accelerated chlorpropamide absorption by magnesium hydroxide was also observed, but the efficacy of chlorpropamide was unaffected.

The relationship between debrisoquine oxidation phenotype and the pharmacokinetics of chlorpropamide.

The pharmacokinetics and urinary metabolite pattern of a single oral dose of chlorpropamide 250 mg have been studied in 6 extensive and 5 poor metabolizers of debrisoquine. Ammonium chloride was given orally to acidify the urine in order to make elimination of the parent drug dependent on metabolism alone. The concentration profile in serum and the pharmacokinetic parameters of the parent drug were similar in both groups. However, the ratio in urine of unchanged chlorpropamide to its hydroxylated metabolites was higher in poor than in extensive metabolizers.

Comparative bioavailability of two brands of chlorpropamide in Kenyans.

The relative bioavailability of two brands of chlorpropamide, Dibonis, and Diabinese has been evaluated in four healthy male volunteers in a randomized, balanced, cross-over study. No statistically significant differences were observed in the absorption rate constant, ka, time to reach peak serum concentration, tp, maximum serum concentration, Cmax, the overall elimination rate constant, kel, and the area under the curve, AUC, at 95% confidence level.