Glyburide/metformin tablets: a new therapeutic option for the management of Type 2 diabetes

Pharmacokinetic and Bioequivalence Studies of 2 Metformin Glibenclamide Tablets in Healthy Chinese Subjects Under Fasting and Fed Conditions

The rational combination of oral antidiabetic agents is more likely to provide better glycemic control than monotherapy. Metformin glibenclamide tablets can be used as second-line therapy for patients with type 2 diabetes mellitus who cannot successfully control their blood glucose levels by diet and exercise plus metformin or sulfonylureas. The aim of this study was to evaluate the bioequivalence and safety of metformin hydrochloride and glibenclamide tablets (500 mg/5 mg) prepared by 2 different vendors in healthy Chinese subjects under fasting and fed conditions. This is an open-label, single-center, randomized, 2-formulation, 2-period crossover study. After screening, 40 subjects were enrolled in the fasting trial, while 40 subjects were enrolled in the fed trial. Qualified subjects were randomly assigned to receive a monotherapy dose of 500 mg/5 mg of the test or reference formulation, and after a 1-week washout period, they took the alternative formulation. Blood samples were collected from 24 blood collection sites per cycle for pharmacokinetic analysis until 36 hours after oral administration. In total, 78 subjects completed the study. Under fasting and fed conditions, the geometric mean ratios of maximum plasma concentration, area under the plasma concentration-time curve (AUC) from time 0 to time of last quantifiable drug level , and AUC from time 0 to infinity between the 2 products, as well as the corresponding 90%CIs, were all within the range of 80%-125%. It was found that exposure (AUC from time 0 to infinity) to metformin is decreased by about 25% in the fed state compared to fasting, whereas glibenclamide exposure is increased by about 30% in the fed state. No severe adverse events were observed in the study.

A randomized, open-label, multicentre, parallel-controlled study comparing the efficacy and safety of biphasic insulin aspart 30 plus metformin with biphasic insulin aspart 30 monotherapy for type 2 diabetes patients inadequately controlled with oral antidiabetic drugs: The merit study

AIM

To confirm non-inferiority of biphasic insulin aspart 30 (BIAsp 30) plus metformin to BIAsp 30 in lowering glycated haemoglobin (HbA1c) in Chinese patients with inadequately controlled type 2 diabetes using oral antidiabetic drugs.

MATERIALS AND METHODS

In this 16-week, prospective, randomized, open-label, multicentre, parallel-controlled study, patients aged 18-79 years with HbA1c ≥7% were randomized to BIAsp 30 plus metformin (n = 130) or BIAsp 30 (n = 127). Initially, 500 mg metformin was administered twice daily and BIAsp 30 was administered at 0.2-0.3 U/kg/d. Changes in HbA1c % from baseline to week 16 as well as secondary and safety endpoints were assessed.

RESULTS

In total, 83.66% of patients in the BIAsp 30 plus metformin (n = 110) and the BIAsp 30 (n = 105) groups completed the study. Mean (±standard deviation) change in HbA1c from baseline to endpoint was -1.74 ± 1.64% and -1.32 ± 2.05% with BIAsp 30 plus metformin and BIAsp 30, respectively. Least squares mean treatment difference was -0.67% (95% CI, -1.06; -0.28). The upper limit of the 95% CI was <0.4 (non-inferiority margin). A significantly higher proportion of individuals reached HbA1c <7% with BIAsp 30 plus metformin than with BIAsp 30 (53.15% vs 35.19%; P = 0.0074). At endpoint, daily BIAsp 30 dose (P < 0.001) and weight gain were significantly lower (P < 0.05) in the BIAsp 30 plus metformin group compared with the BIAsp 30 group. No between-group differences in number of hypoglycaemic events were observed.

CONCLUSION

BIAsp 30 plus metformin was non-inferior to BIAsp 30 in safely reducing HbA1c in this study.

Bilayer matrix tablets for prolonged actions of metformin hydrochloride and repaglinide

A combination therapy of metformin hydrochloride (MH) and repaglinide (RG) achieves a perfect glycemic control; however, the combination formulation of immediate release must be taken several times a day, compromising the therapeutic benefits and causing inconveniences to the patients. Herein, a bilayer matrix tablet that aimed at continuously releasing both MH and RG over time was developed, in which the two drugs were formulated into two separated layers. The tablets were prepared by wet granulation method, and the optimized formulation was obtained by evaluating the factors that affected the drug release. The bilayer tablets simultaneously released the two drugs over 12 h; and a better in vivo performance with a steady plasma concentration, markedly lower Cmax, prolonged Tmax, and perfect absorption was obtained. Summarily, the bilayer matrix tablets sustained both MH and RG release over time, thereby prolonging the actions for diabetic therapy and producing better health outcomes.

Fast and environmentally friendly quantitative analysis of active agents in anti-diabetic tablets by an alternative laser-induced breakdown spectroscopy (LIBS) method and comparison to a validated reversed-phase high-performance liquid chromatography (RP-HPLC) method

Laser-induced breakdown spectroscopy (LIBS) is evaluated as a potential analytic technique for rapid screening and quality control of anti-diabetic tablets. This paper proposes a simple LIBS-based method for the quantitative analysis of two active pharmaceutical ingredients (APIs): metformin (Met) and glybenclamide (Gly). In order to quantify both APIs, chlorine (Cl) concentration was estimated by employing the Cl/Br optical emission ratio, where Br was introduced as internal standard. Calibration curves were prepared, achieving linearity higher than 99%. On the other hand, for comparison to the proposed method, an isocratic reversed-phase high-performance liquid chromatography (RP-HPLC) method was also developed for quantitative determination of the same analytes by ultraviolet (UV) detection. The chromatographic separation was achieved on a Phenomenex Hypersil C18, 250 mm × 4.6 mm, 5 μm column. The mobile phase was K(2)HPO(4)/H(3)PO(4)-CH(3)OH and flow rate was 1.0 mL min(-1). The method is linear over a range of 10-60 μg mL(-1) for Gly and 5-30 μg mL(-1) for Met and the correlation coefficients were ≥0.99. Recoveries were found to be in the range of 95-101%. Furthermore, four different commercial brands of each active agent were evaluated by both proposed LIBS and chromatographic methods and results were compared with each other. The comparison was satisfactorily validated by analysis of variance (ANOVA).

LC-MS/MS-ESI method for simultaneous quantitation of metformin and repaglinidie in rat plasma and its application to pharmacokinetic study in rats

A highly sensitive and specific LC-MS/MS-ESI method has been developed for simultaneous quantification of metformin (MFN) and repaglinide (RGN) in rat plasma (50 μL) using phenacetin as an internal standard (IS). Simple protein precipitation was used to extract MFN and RGN from rat plasma. The chromatographic resolution of MFN, RGN and IS was achieved with a mobile phase consisting of 0.2% formic acid in water-acetonitrile (1:1, v/v) with a time program flow gradient on a Chromolith RP-18e column. The total chromatographic run time was 3.5 min and the elution of MFN, RGN and IS occurred at 1.64, 2.21 and 2.15 min, respectively. A linear response function was established for the range of concentrations 0.855-394 and 0.021-21.7 ng/mL for MFN and RGN, respectively. The intra- and inter-day precision values for MFN and RGN met the acceptance as per FDA guidelines. MFN and RGN were stable in battery of stability studies viz., bench-top, auto-sampler and freeze-thaw cycles. The developed assay was applied to a pharmacokinetic study in rats.

Pharmacokinetics of metformin after enteral administration in insulin-resistant ponies

OBJECTIVE

To determine pharmacokinetics and plasma steady-state kinetics of metformin after oral or nasogastric administration in insulin-resistant (IR) ponies.

ANIMALS

8 IR ponies.

PROCEDURES

Metformin (30 mg/kg) was administered to 8 ponies via nasogastric tube Blood samples were collected at intervals for 24 hours. Plasma concentrations of metformin were measured via liquid chromatography-electrospray tandem mass spectroscopy Pharmacokinetic variables were determined via noncompartmental analysis. Metformin (15 mg/kg, PO, twice daily [8 am and 5 pm]) was administered to 4 ponies for an additional 20 days, and blood samples were obtained every 2 days. Plasma concentration at steady state (Css) was determined.

RESULTS

Mean±SD elimination half-life (t1/2) of metformin was 11.7±5.2 hours, maxima plasma concentration was 748±269 ng/mL at 54±32 minutes, mean area under the curve was 355±92 microg.h/mL, and apparent clearance was 90.6±28.1 mL/min/kg. The Css was 122±22 ng/mL.

CONCLUSIONS AND CLINICAL RELEVANCE

Metformin reportedly enhances insulin sensitivity of peripheral tissues without stimulating insulin secretion, but bioavailability in horses is low. The t1/2 of metformin in IR ponies was similar to that in humans. Actual clearance of metformin adjusted for bioavailability in IR ponies was similar to that in humans; however, during chronic oral administration at dosages reported in efficacy studies, the Css of metformin was less than values associated with therapeutic efficacy in humans The apparent lack of long-term efficacy of metformin in horses is likely attributable to low bioavailability, rather than to rapid clearance.

Treatment of type 2 diabetes mellitus with orally administered agents: advances in combination therapy

OBJECTIVE

To discuss the effects and clinical benefit provided by combining various orally administered antidiabetic drugs (OADs) for the treatment of type 2 diabetes and to examine the advantages of single-tablet combinations with respect to targeting hyperglycemia and adherence.

METHODS

A review of randomized controlled trials that studied OAD combinations for the treatment of type 2 diabetes was conducted by using search terms in PubMed.

RESULTS

Reported data have documented that OAD combination therapies have additional benefits over monotherapy in terms of glycemic efficacy. Results from randomized controlled trials on a range of OAD combinations have demonstrated differences in safety and efficacy. The use of single-tablet OAD combinations has been shown to improve adherence in patients.

CONCLUSION

The development of single-tablet OAD combinations that can address all aspects of glycemia with a favorable tolerability profile has the potential to help patients manage their glycemic control more effectively and to minimize the risk of long-term diabetes-related complications. In addition, single-tablet combinations of agents offer improved convenience for patients as well as potential cost benefits. Thus, they represent an important treatment option for type 2 diabetes.

Efficacy of glimepiride/metformin combination versus glibenclamide/metformin in patients with uncontrolled type 2 diabetes mellitus

AIM

The aim of this study was to compare the efficacy of glimepiride/metformin combination versus glibenclamide/metformin for reaching glycemic control in patients with uncontrolled type 2 diabetes mellitus.

PATIENTS AND METHODS

A randomized, double-blind, multicenter clinical trial was performed in 152 uncontrolled type 2 diabetic patients. Serum fasting and postprandial glucose, hemoglobin A1c (A1C), high-density lipoprotein cholesterol, and triglycerides were measured. After random allocation, all patients received two pills of glimepiride (1 mg)/metformin (500 mg) or glibenclamide (5 mg)/metformin (500 mg) po once a day. Dosage was increased to a maximum of four pills in order to reach the glycemic control goals (fasting glucose <or=7.2 mmol/l, postprandial glucose <10.0 mmol/l, A1C <7%, or an A1C >or=1% reduction). Statistical analyses were carried out using chi-square, ANOVA, or Student's t test. The protocol was approved by an ethics committee and met all requirements needed to perform research in human subjects; all patients gave written informed consent.

RESULTS

Each study group included 76 patients. No significant differences in basal clinical and laboratory characteristics between groups were found. At the end of the study, A1C concentration was significantly lower in the glimepiride/metformin group (P=.025). A higher proportion of patients from the glimepiride group (44.6% vs. 26.8%, P<.05) reached the goal of A1C <7% at 12 months of treatment. A higher proportion of hypoglycemic events were observed in the glibenclamide group (28.9% vs. 17.1%, P<.047).

CONCLUSION

Glimepiride/metformin demonstrated being more efficacious than glibenclamide/metformin at reaching the glycemic control goals with less hypoglycemic events in patients with uncontrolled type 2 diabetes mellitus.

Fixed combination of repaglinide and metformin in the management of type 2 diabetes

Treatment to target fasting blood glucose (FBG), postprandial glucose (PPG) and HbA(1c) are essential in the management of type 2 diabetes to reduce the risk of vascular complications. Early combination therapy with oral agents is increasingly being seen as important to achieve this. Repaglinide, a rapid-acting insulin secretagogue, targets PPG, and metformin, an insulin sensitizer, targets FBG. Because of their complementary modes of action these therapies are frequently given as combination therapy in separate tablets. To overcome the issues with adherence to multiple tablets, repaglinide and metformin are now available in a fixed-dose combination (FDC). Repaglinide/metformin FDC is bioequivalent to each tablet given separately, suggesting that the efficacy and safety profile is similar. There is no effect of food on repaglinide when in the FDC. Repaglinide/metformin FDC is as effective in reducing HbA(1c) and FBG whether given twice or three times daily, with a similar safety profile. Repaglinide/metformin FDC twice daily is as effective in reducing HbA(1c) and FBG as rosiglitazone/metformin FDC with a similar safety profile, but unlike the rosiglitazone/metformin FDC, repaglinide/metformin FDC improves the lipid profile. Repaglinide/metformin FDC represents a new option in the pursuit of achieving glucose targets and reducing vascular risk in type 2 diabetes, with the advantage of improving adherence.

The value, qualification, and regulatory use of surrogate end points in drug development

The acceptance and use of either surrogate end points (SEPs) or efficient clinical end points are associated with greater and more rapid availability of new medicines as compared with disease situations for which clinical end points are inefficient or no surrogates exist. This review of the history of the development, qualification, and acceptance of key SEPs shows that both successes and failures had three key characteristics: (i) apparent biologic plausibility, (ii) prognostic value for the outcome of the disease, and (iii) an association between changes in the SEP and changes in outcome with therapeutic intervention--the three factors recommended for SEPs in the International Conference on Harmonisation's "Statistical Principles for Clinical Trials." We recommend that only prognostic value be an absolute prerequisite for surrogacy, because therapeutic interventions may not exist a priori, and biological plausibility can be subjective. Ideally, all three of these factors would be traded off against one another in a consistent and transparent risk-management process.

Oral combination therapy: repaglinide plus metformin for treatment of type 2 diabetes

Type 2 diabetes is characterized by decreases in insulin secretion and insulin sensitivity. Several classes of oral antidiabetic medications are currently approved for the treatment of type 2 diabetes. A stepwise treatment approach from monotherapy to combination therapy is traditionally used; however, the frequency of treatment failure with monotherapy has resulted in a move towards earlier treatment with combination therapies that target the two principal defects in glycaemic control. One such combination regimen is repaglinide (a prandial glucose regulator that increases insulin release) plus metformin (an insulin sensitizer that inhibits hepatic glucose output, increases peripheral glucose uptake and utilization and minimizes weight gain). Findings from several clinical trials have shown that combination therapy with repaglinide plus metformin is well tolerated and results in greater reductions of haemoglobin A(1c) and fasting plasma glucose values compared with either monotherapy. Repaglinide may also provide a more suitable alternative to combination therapy with sulphonylureas and metformin because of its reduced propensity for hypoglycaemia. The combination regimen of repaglinide plus metformin should therefore be considered as a valuable option in the management of patients with type 2 diabetes when monotherapy is no longer adequate.

Metformin and body weight

Most patients with type 2 diabetes are overweight or obese, overweight or obesity increases the risk of developing type 2 diabetes and obesity per se is strongly associated with multiple cardiometabolic risk factors. However, many antidiabetic treatments increase body weight. The oral antidiabetic agent, metformin, has been evaluated in hundreds of clinical studies in diverse patient populations during approximately five decades of clinical use. This review summarizes the effects of metformin on body weight, with special reference to studies of longer duration (>/=6 months) as both diabetes and obesity are long-term conditions. Approximately half of studies in drug-naive type 2 diabetic patients demonstrated significant weight loss with metformin compared with baseline or comparator drugs, although pooled analyses have suggested no significant effect versus placebo. Similarly, metformin has been shown to induce weight loss in obese nondiabetic populations, although studies of long duration in this population are scarce. Metformin does appear to mitigate the adverse effects of insulin on body weight. The weight-neutral or weight-sparing effects of metformin constitute a therapeutic advantage in diabetes management where other first-line oral antidiabetic treatments often promote clinically significant weight gain.

Multi-component plasma quantitation of anti-hyperglycemic pharmaceutical compounds using liquid chromatography-tandem mass spectrometry

Type-2 diabetes is a disorder characterized by disrupted insulin production leading to high blood glucose levels. To control this disease, combination therapy is often used. Hypoglycemic agents such as metformin, glipizide, glyburide, repaglinide, rosiglitazone, nateglinide, and pioglitazone are widely prescribed to control blood sugar levels. These drugs provide the basis for the development of a quantitative multianalyte bioanalytical method. As an example, a highly sensitive and selective multi-drug method based on liquid chromatography tandem mass spectrometry (LC-MS/MS) was developed. This rapid, automated method consists of protein precipitation of 20 microL of plasma coupled with gradient HPLC elution of compounds using 10 mM ammonium formate buffer and 0.1% formic acid in acetonitrile as the mobile phases. MS/MS detection was performed using turbo ion spray in the positive ion multiple reaction monitoring (SRM) mode. A lower limit of quantitation (LLQ) in a range of 1.0-5.0 ng/mL was achieved for all analytes. The linearity of the method was observed over a 500-fold dynamic range. Drug recoveries ranged from 86.2 to 94.2% for all analytes of interest. Selectivity, sample dilution, intra-day and inter-day accuracy and precision, and stability assessment were evaluated for all compounds.

Investigation of the pharmacokinetic and pharmacodynamic interactions between memantine and glyburide/metformin in healthy young subjects: a single-center, multiple-dose, open-label study

BACKGROUND

The high prevalence rates of both Alzheimer's disease (AD) and type 2 diabetes mellitus in the elderly population suggest that concomitant pharmacotherapy is likely. Given the renal tubular transport and extensive urinary excretion of memantine and metformin, it was of interest to assess the pharmacokinetic and pharmacodynamic interaction with glyburide/metformin.

OBJECTIVE

The primary goal of this study was to determine whether an in vivo pharmacokinetic or pharmacodynamic interaction exists between memantine (an uncompetitive, moderate-affinity, N-methyl-D-aspartate receptor antagonist with fast blocking/unblocking kinetics that is available in the United States for moderate to severe AD) and glyburide/metformin (a combination pharmacotherapy formulation approved for glycemic control in patients with type 2 diabetes mellitus).

METHODS

In this single-center, multiple-dose, open-label study, healthy adult subjects received a single oral dose of memantine hydrochloride (20 mg) on day 1. After a 14-day washout period, subjects were orally administered 1.25-mg glyburide/250-mg metformin BID with food for 6 days. On day 21, subjects were coadministered memantine (20 mg) and glyburide/metformin with food. Assessments included determination of pharmacokinetic parameters for memantine and the antidiabetic agents when administered alone and in combination, pharmacodynamic measurements of blood glucose levels, and analyses of tolerability.

RESULTS

The study population consisted of 24 subjects (13 women, 11 men; 79.2% white) with a mean (SD) age of 26.1 (5.6) years and a mean (SD) weight of 69.5 (11.3) kg. Twenty-one subjects completed the study: 2 discontinued due to adverse events judged unrelated to study medication, and 1 withdrew consent. No significant pharmacokinetic or pharmacodynamic interactions were observed between memantine and glyburide/metformin. Adverse events included dizziness (41.7% of patients) with memantine administration and gastrointestinal effects (nausea, 9.1 %; vomiting, 9.1%; abdominal cramps, 13.6%) with glyburide/metformin administration.

CONCLUSIONS

No pharmacokinetic interactions between memantine and glyburide/metformin were detected in this study of healthy young volunteers. Memantine had no effect on the pharmacodynamic activities of glyburide and metformin, and the drug combination was well tolerated in this population.

Diabetes mellitus in a domesticated Spanish Mustang

An 18-year-old Spanish Mustang mare was referred for evaluation of progressive weight loss and persistent hyperglycemia. Clinicopathologic abnormalities included marked hyperglycemia and glycosuria. Serum cortisol concentration was appropriately decreased following administration of dexamethasone, indicating that the horse did not have pituitary pars intermedia dysfunction. Serum insulin and plasma C-peptide concentrations were low, suggesting that hyperglycemia was a result of decreased secretion of insulin by pancreatic beta cells. In addition, glucose concentration did not return to the baseline concentration until 5 hours after i.v. administration of a glucose bolus, suggesting that insulin secretion, insulin effect, or both were reduced. However, i.v. administration of insulin caused only a slight decrease in the plasma glucose concentration, giving the impression that the action of insulin was impaired. Within 5 hours after administration of a combination of glyburide and metformin, which is used to treat diabetes mellitus in humans, the glucose concentration was within reference limits. The horse was euthanized, and a postmortem examination was done. Immunohistochemical staining of sections of the pancreas revealed attenuation of the pancreatic islet beta-cell population, with beta cells that remained generally limited to the periphery of the islets. These findings indicate that, albeit rare, pancreatic beta-cell failure may contribute to the development of diabetes mellitus in horses.

Development and validation for high selective quantitative determination of metformin in human plasma by cation exchanging with normal-phase LC/MS/MS

An assay based on cation exchange solid-phase extraction and liquid chromatography-tandem mass spectrometry (LC/MS/MS) has been developed for the quantitative determination of metformin in human plasma. The analytical method consists of cation exchange solid-phase extraction (VersaPlate CBA) without any further evaporation/dissolution steps and cation exchange-based HPLC separation (Capcell Pak SCX column) with a normal-phase gradient system followed by semi-micro LC/MS/MS in positive ion selected reaction monitoring mode using electrospray ionization. The method exhibited excellent performance in terms of selectivity, robustness, short run time (7 min/sample) and simplicity of sample preparation. The calibration range was 10-1000 ng/ml with 0.2 ml of plasma. Intra- and inter-day mean accuracies were within the ranges of 100.3-105.0% and 101.2-105.3%, respectively. Intra- and inter-day precisions were within the ranges of 0.8-1.9% and 1.5-8.6%, respectively. Mean absolute recovery was 67.0% for metformin. No apparent loss of metformin after extraction was observed in an autosampler at 10 degrees C for 24 h. Dilution of metformin by blank human plasma up to 20-fold was tested and revealed no impact on the results of determination. Furthermore, the method exhibited high selectivity, since no effect on metformin analysis was observed on comparison of samples with or without nateglinide and other agents in plasma. Results obtained with the method were also comparable to a published LC-UV method on cross-validation. This method can be applied to various clinical pharmacokinetic studies of metformin.

Tolerability Profile of Metformin/Glibenclamide Combination Tablets (Glucovance??)

It is important to manage blood glucose intensively in patients with type 2 diabetes mellitus in order to reduce the risk of long-term complications. Oral combination therapy that addresses insulin resistance and beta-cell dysfunction is a proven means of improving glycaemic control when monotherapy becomes insufficiently effective. Metformin/glibenclamide (glyburide) combination tablets were developed to provide a means of applying this strategy while minimising polypharmacy. This review examines the tolerability profile of this treatment from four double-blind, randomised clinical trials in a total of 2342 type 2 diabetic patients with hyperglycaemia despite treatment with diet and exercise, a sulphonylurea or metformin. Treatment with combination tablets was associated with markedly superior blood glucose control, at lower doses of metformin and glibenclamide, compared with monotherapies. The incidence of symptoms of hypoglycaemia varied between dosages and trials, though the incidence of severe or biochemically confirmed hypoglycaemia or withdrawals from clinical trials for this reason was consistently low and comparable with glibenclamide alone. No patient required third-party assistance for hypoglycaemia. Significantly fewer diet-failed patients receiving low-dose combination tablets reported gastrointestinal adverse effects compared with metformin alone, with a comparable incidence between metformin and combination tablets in post-monotherapy studies. The incidence of other adverse events, including serious adverse events, was similar for combination tablets and monotherapies. The lower doses of metformin and glibenclamide with the combination tablet approach, and the design of the combination tablets themselves, may underlie the beneficial tolerability profile of this treatment.