Differential interaction of glimepiride and glibenclamide with the beta-cell sulfonylurea receptor. I. Binding characteristics

Evaluation of Effect of Nishamalaki on STZ and HFHF Diet Induced Diabetic Neuropathy in Wistar Rats

INTRODUCTION

Diabetic neuropathy is one of the most common complications affecting 50% of diabetic patients. Neuropathic pain is the most difficult types of pain to treat. There is no specific treatment for neuropathy. Nishamalaki (NA), combination of Curcuma longa and Emblica officinalis used to treat Diabetes Mellitus (DM). So, efforts were made to test whether NA is useful in prevention of diabetic neuropathy.

AIM

To evaluate the effect of NA on diabetic neuropathy in type 2 diabetic wistar rats.

MATERIALS AND METHODS

Group I (Control) vehicle treated consists of 6 rats. Diabetes induced in 36 wistar rats with Streptozotocin (STZ) (35mg/kg) intra-peritoneally followed by High Fat High Fructose diet. After confirmation of development of diabetes; rats divided into six groups (n=6). Group II - VII Diabetic Control, NA low dose, NA High dose, Glibenclamide, Pioglitazone and Epalrestat. Animals received drug treatment for next 12 weeks. Monitoring of Blood Sugar Level (BSL) done every 15 days and lipid profile at the end. Eddy's hot plate and tail immersion test performed to assess thermal hyperalgesia and cold allodynia. Walking function test performed to assess motor function.

RESULTS

Diabetic rats exhibited significant (p<0.001) hyperalgesia and increased BSL compared to control rats. Dose-dependent improvement was observed in thermal hyperalgesia & cold allodynia in NA groups. Activity of NA was more than Glibenclamide, Epalrestat and Pioglitazone in high dose and comparable in low dose. Nishamalaki improved lipid profile.

CONCLUSION

Apart from controlling hyperglycaemia and reducing lipid levels, NA effectively prevented the development of diabetic neuropathy.

Risk of hypoglycaemia in users of sulphonylureas compared with metformin in relation to renal function and sulphonylurea metabolite group: population based cohort study

OBJECTIVE

 To determine the association between use of sulphonylureas and risk of hypoglycaemia in relation to renal function and sulphonylurea metabolic group compared with use of metformin.

DESIGN

 Population based cohort study using routinely collected data from general practices in England.

SETTING

 Clinical Practice Research Datalink (CPRD) database, 2004-12.

PARTICIPANTS

 120 803 new users of a non-insulin antidiabetic agent with at least one prescription and aged 18 years or more. The first prescription defined start of follow-up. Patients were followed until the end of data collection, a record for hypoglycaemia, or a blood glucose level of less than 3.0 mmol/L.

MAIN OUTCOME MEASURES

 Associations between sulphonylurea dose, renal impairment, type of sulphonylurea used, and risk of hypoglycaemia, were determined using Cox proportional hazard models. Adjustments were made for age, sex, lifestyle, comorbidity, and drug use.

RESULTS

 The risk of hypoglycaemia in current users of sulphonylureas only was significantly increased compared with current users of metformin only (adjusted hazard ratio 2.50, 95% confidence interval 2.23 to 2.82). The higher risk in current users of sulphonylureas only was further increased in patients with an estimated glomerular filtration rate of less than 30 mL/min/1.73 m(2) (4.96, 3.76 to 6.55). The risk of hypoglycaemia was also significantly higher in patients with a high sulphonylurea dose (3.12, 2.68 to 3.62) and in current users of glibenclamide (7.48, 4.89 to 11.44). Gliclazide, the sulphonylurea of first choice, showed a similar risk of hypoglycaemia compared with other sulphonylureas.

CONCLUSIONS

 Sulphonylurea treatment in patients with a renal function of less than 30 mL/min/1.73 m(2) should be considered with caution. Moreover, an increased risk of hypoglycaemic events was observed among all users of sulphonylureas. This contrasts with several guidelines that recommend gliclazide as first choice sulphonylurea, and therefore requires further investigation.

Simultaneous Determination of Bosentan, Glimepiride, HYBOS and M1 in Rat Plasma by UPLC-MS-MS and its Application to Pharmacokinetic Study

A rapid and sensitive ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS-MS) method for the simultaneous determination of bosentan (BOS), glimepiride (GLP), hydroxyl bosentan (HYBOS) and hydroxyl glimepiride (M1) in rat plasma using one-step protein precipitation was developed and validated. After addition of ambrisentan as an internal standard (IS), protein precipitation by acetonitrile was used in sample preparation. Chromatographic separation was achieved on a Waters ACQUITY UPLC BEH C18 column (2.1 mm × 100 mm, 1.7 μm particle size, Waters Corp., Milford, MA, USA) and inline 0.2 μm stainless steel frit filter (Waters Corp.) with acetonitrile-0.1% formic acid as the mobile phase at a flow rate of 0.4 mL/min with gradient elution. The column temperature was maintained at 40°C. Only 4 min was needed for an analytical run. The retention times were ∼3.29 min for BOS, 3.56 min for GLP, 1.42 min for HYBOS, 1.53 min for M1 and 3.22 min for IS. Electrospray ionization source was employed and operated in positive-ion mode; multiple reaction monitoring mode was applied to target fragment ions m/z 552 → 202, m/z 568 → 202, m/z 491 → 352, m/z 507 → 352 and m/z 379 → 347 for BOS, HYBOS, GLP, M1 and IS, respectively. The assay was validated over concentration ranges of 25-5,000 ng/mL (r(2) = 0.9984) for BOS, 1-200 ng/mL (r(2) = 0.9999) for GLP, 0.5-100 ng/mL (r(2) = 0.9999) for HYBOS and 0.1-20 ng/mL (r(2) = 0.9984) for M1. Intra- and interday precision values for replicate quality control samples were within 14.2% for all analytes during the assay validation. Mean quality control accuracy values were within -3.3 to 14.4% of nominal values for all analytes. The mean recoveries of BOS, GLP, HYBOS, M1 and ambrisentan from the plasma exceeded 90.4%. The analytes were stable in rat plasma for at least 2 h at room temperature, 30 days at -40°C and following at least three freeze-thaw cycles (-40°C to room temperature). This method was successfully applied to a pharmacokinetic study of coadministeration of BOS and GLP in rats.

Place of sulfonylureas in the management of type 2 diabetes mellitus in South Asia: A consensus statement

Since their introduction in clinical practice in the 1950's, Sulfonylureas (SUs) have remained the main-stay of pharmacotherapy in the management of type 2 diabetes. Despite their well-established benefits, their place in therapy is inappropriately being overshadowed by newer therapies. Many of the clinical issues associated with the use of SUs are agent-specific, and do not pertain to the class as such. Modern SUs (glimepiride, gliclazide MR) are backed by a large body of evidence, experience, and most importantly, outcome data, which supports their role in managing patients with diabetes. Person-centred care, i.e., careful choice of SU, appropriate dosage, timing of administration, and adequate patient counseling, will ensure that deserving patients are not deprived of the advantages of this well-established class of anti-diabetic agents. Considering their efficacy, safety, pleiotropic benefits, and low cost of therapy, SUs should be considered as recommended therapy for the treatment of diabetes in South Asia. This initiative by SAFES aims to encourage rational, safe and smart prescription of SUs, and includes appropriate medication counseling.

Counterregulatory responses to hypoglycemia differ between glimepiride and glyburide in non diabetic individuals

OBJECTIVE

Reported rates of hypoglycemia in patients with type 2 diabetes mellitus are lower with glimepiride as compared to glyburide. The aim of this study was to determine whether physiologic differences in counterregulatory neuroendocrine and metabolic mechanisms during hypoglycemia provide a basis for the observed clinical differences between glimepiride and glyburide.

RESEARCH DESIGN AND METHODS

Non-diabetic volunteers (age 38±2years, BMI 26±1kg/m(2)) were studied in a single-blind fashion during separate 2day randomized protocols consisting of 2h hyperinsulinemic (9pmol/kg/min) euglycemic (4.9±0.1mmol) and hypoglycemic (2.9±0.1mmol/L) clamps. Individuals received biologically equivalent doses of glimepiride (4mg) or glyburide (10mg) 1h prior to each glucose clamp (n=11) as well as a control group of placebo studies. Glucose kinetics were calculated using D-Glucose-6-6d2.

RESULTS

Insulin and C-peptide levels were increased (p<0.05) during euglycemia in both sulfonylurea groups as compared to placebo. However, despite equivalent hypoglycemia, insulin and C-peptide levels were higher (p<0.05) only after glyburide. Glucagon responses and endogenous glucose production (EGP) were decreased (p<0.05) during hypoglycemia following glyburide administration as compared to glimepiride. Glyburide reduced (p<0.05) norepinephrine responses during euglycemic clamps. In addition combined epinephrine and norepinephrine responses during hypoglycemia were reduced (p<0.05) following glyburide as compared to placebo. Leptin levels fell by a greater amount (p<0.05) during hypoglycemia with both sulfonylureas as compared to placebo.

CONCLUSIONS

In summary, glimepiride and glyburide can both similarly increase insulin and C-peptide levels during hyperinsulinemic euglycemia. However, during moderate hyperinsulinemic hypoglycemia (2.9mmol/L) glyburide resulted in increased C-peptide and insulin, but blunted glucagon, sympathetic nervous system and EGP responses. We conclude that glyburide can acutely reduce key neuroendocrine and metabolic counterregulatory defenses during hypoglycemia in healthy individuals.

CYP2C metabolism of oral antidiabetic drugs--impact on pharmacokinetics, drug interactions and pharmacogenetic aspects

INTRODUCTION

The cytochrome P4502C enzymes account for the metabolism of approximately 20% of therapeutic drugs including certain oral antidiabetic drugs (OADs).

AREAS COVERED

This review focuses on the effect of CYP2C enzymes on metabolism of sulphonylureas (SUs), meglitinides, and thiazolidinediones (TZDs) discussing their impact on pharmacokinetics, drug interactions and toxicological profiles. Pharmacogenetic aspects reflecting individual gene variants and variable drug effects are also considered.

EXPERT OPINION

Genetic polymorphisms of CYP2C9 enzymes (*2/*2, *2/*3, *3/*3) influence the glycaemic response to SUs and impair their substrate metabolism. Restricted data from small-sized studies with heterogenous definitions of hypoglycaemia revealed no clear association between CYP2C9 genotypes and the risk of hypoglycaemia. Functional polymorphisms of CYP2C8- and CYP2C9 drug metabolizing genes affect markedly pharmacokinetics of meglitinides. Compared to wild-type carriers, patients treated with TZDs and carrying the common CYP2C8*3 and *4 variants showed a reduced glycaemic control. The strong CYP2C8 and OATP1B1 inhibitor gemfibrozil increases substantially the plasma concentrations of repaglinide and TZDs. Numerous metabolic drug interactions exist between SUs and commonly prescribed drugs, especially anti-infectives. The complex pharmacokinetic and pharmacogenetic properties and the unfavourable short and long term risk profile of glibenclamide and glimepiride raise the question whether their use can be justified any longer.

Glimepiride: evidence-based facts, trends, and observations (GIFTS). [corrected]

Type 2 diabetes mellitus is characterized by insulin resistance and progressive β cell failure; therefore, β cell secretagogues are useful for achieving sufficient glycemic control. Glimepiride is a second-generation sulfonylurea that stimulates pancreatic β cells to release insulin. Additionally, is has been shown to work via several extra pancreatic mechanisms. It is administered as monotherapy in patients with type 2 diabetes mellitus in whom glycemic control is not achieved by dietary and lifestyle modifications. It can also be combined with other antihyperglycemic agents, including metformin and insulin, in patients who are not adequately controlled by sulfonylureas alone. The effective dosage range is 1 to 8 mg/day; however, there is no significant difference between 4 and 8 mg/day, but it should be used with caution in the elderly and in patients with renal or hepatic disease. In clinical studies, glimepiride was generally associated with lower risk of hypoglycemia and less weight gain compared to other sulfonylureas. Glimepiride use may be safer in patients with cardiovascular disease because of its lack of detrimental effects on ischemic preconditioning. It is effective in reducing fasting plasma glucose, post-prandial glucose, and glycosylated hemoglobin levels and is a useful, cost-effective treatment option for managing type 2 diabetes mellitus.

Drug-induced hypoglycaemia in type 2 diabetes

INTRODUCTION

Hypoglycaemia is a side effect caused by some therapies for type 2 diabetes, which can cause physical, social and psychological harm. Hypoglycaemia also prevents attainment of treatment goals and satisfactory glycaemic control.

AREAS COVERED

The risk of hypoglycaemia associated with commonly prescribed therapies, including metformin, sulphonylureas, dipeptidyl peptidase-4 enzyme (DPP-4) inhibitors, glucagon-like peptide-1 (GLP-1) agonists and thiazolidinediones, is reviewed in this paper (insulin-induced hypoglycaemia is not included). Other medications that are frequently co-prescribed in type 2 diabetes are also discussed, including anti-hypertensive drugs, antibiotics and fibrates, along with various important patient-related risk factors.

EXPERT OPINION

Hypoglycaemia is a common and potentially dangerous side effect of some medications used for type 2 diabetes. The risk of hypoglycaemia should always be considered when selecting and implementing a therapy, with a focus on the individual. Future research into new therapies should measure the frequency of hypoglycaemia prospectively and accurately. Hypoglycaemia has been shown to be a potentially life-threatening metabolic stress; therefore therapies that effectively manage diabetes without the risk of hypoglycaemia are likely to be favoured in the future.

Effect of genetic polymorphisms on the pharmacokinetics and efficacy of glimepiride in a Korean population

BACKGROUNDS

Glimepiride is a commonly used sulfonylurea hypoglycemic agent. There is considerable interindividual variation in the response to sulfonylurea for patients with type 2 diabetes. The purpose of this study was to investigate whether genetic variations influence the efficacy of glimepiride in healthy Korean subjects.

METHODS

A single 2-mg oral dose of glimepiride was administered to 46 healthy volunteers. Serial blood sampling for 12h after oral dosing was performed for determination of plasma glimepiride, glucose and insulin levels. We tested the association of seven single nucleotide polymorphisms (SNPs) in four candidate genes with the efficacy of glimepiride.

RESULTS

Pharmacodynamic profiles for plasma glucose and insulin showed no statistically significant differences among genotype groups, and parameters were not different from one another. There were no association of the KCNJ11, NOS1AP, TCF7L2 and ABCC8 gene polymorphisms and the efficacy of glimepiride.

CONCLUSIONS

Knowledge of these polymorphisms provides no clinical useful information for the pharmacogenetic therapeutic approach for Korean patients with type 2 diabetes.

The role of glimepiride in the treatment of type 2 diabetes mellitus

IMPORTANCE OF THE FIELD

Type 2 diabetes mellitus (T2DM) is increasingly prevalent throughout the world; controlling glycemia is an important part of preventing serious complications of diabetes. Sulfonylureas have been used in the treatment of type 2 diabetes for many years.

AREAS COVERED IN THIS REVIEW

This article reviews the pharmacological and clinical aspects of glimepiride, a second-generation sulfonylurea. Literature search was conducted in PubMed, and articles selected for relevance to pharmacology or clinical efficacy data from 1994 to 2009, with older references sought as indicated.

WHAT THE READER WILL GAIN

Pharmacology of glimepiride, data regarding clinical efficacy, key comparisons to other agents and emerging concepts related to glimepiride are discussed.

TAKE HOME MESSAGE

Therapy with glimepiride improves the relative insulin secretory deficit found in T2DM, has antihyperglycemic efficacy equal to other secretagogues with reduced potential for hypoglycemia and may have additional actions contributing to glycemic control in T2DM.

Novel glimepiride derivatives with potential as double-edged swords against type II diabetes

Sulphonylurea drugs have been widely used in the safe and efficacous therapy of type II diabetes during the past five decades. They lower blood glucose predominantly via the stimulation of insulin release from pancreatic beta-cells. However, a moderate insulin-independent regulation of fatty acid esterification and release in adipose tissue cells has been reported for certain sulphonylureas, in particular for glimepiride. On basis of the known pleiotropic pathogenesis of type II diabetes with a combination of beta-cell failure and peripheral, including adipocyte, insulin resistance, anti-diabetic drugs exerting both insulin releasing- and fatty acid-metabolizing activities in a more balanced and potent fashion may be of advantage. However, the completely different molecular mechanisms underlying the insulin-releasing and fatty acid-metabolizing activities, as have been delineated so far for glimepiride, may hamper their optimization within a single sulphonylurea molecule. By analyzing conventional sulphonylureas and novel glimepiride derivatives for their activities at the primary targets and downstream steps in both beta-cells and adipocytes in vitro we demonstrate here that the insulin-releasing and fatty acid-metabolizing activities are critically dependent on both overlapping and independent structural determinants. These were unravelled by the parallel losses of these two activities in a subset of glimepiride derivatives and the impairment in the insulin-releasing activity in parallel with elevation in the fatty acid-metabolizing activity in a different subset. Together these findings may provide a basis for the design of novel sulphonylureas with blood glucose-lowering activity relying on less pronounced stimulation of insulin release from pancreatic beta-cells and more pronounced insulin-independent stimulation of esterification as well as inhibition of release of fatty acids by adipocytes than provoked by the sulphonylureas currently used in therapy.

Oral antidiabetic drug metabolism: pharmacogenomics and drug interactions

BACKGROUND

Type 2 diabetes is progressive in nature and so to control cardiovascular risk, most patients need combinations of oral antidiabetic drugs (OADs) plus or minus insulin. Thus, drug-drug interactions may substantially contribute to harmful effects of intensive glucose lowering therapy.

METHODS

A PubMed literature search was performed to select the most recent and relevant publications examining OAD metabolism and the effects of concomitant use of OADs.

RESULTS/CONCLUSION

Considering the individual sensitivity to OADs, pharmacogenetic factors could be of critical importance. The therapeutic range and efficacy as well as adverse effects of OADs may be significantly affected by genetic polymorphisms of cytochrome P450 drug metabolising enzymes, organic cation transporters or organic anion transporting polypeptides. Although current data suggest that modest pharmacokinetics interferences among some OAD combinations exist, they do not seem to have substantial clinical consequences. As long-term adherence to multi-drug treatment is poor in diabetic patients, the future will show a strong move towards earlier treatment with combination therapies. As metformin is cardiovascular protective and is not metabolised through the hepatic cytochrome P450 system, it is a key compound for any OAD combination. There is an overwhelming amount of small-sized in vitro studies and investigations mostly including healthy volunteers dealing with short-term effects and surrogate parameters of concomitant OAD use. Further evidence from large-scale studies including typical subjects with type 2 diabetes, in particular multimorbid and geriatric patients with polypharmacy, is needed. Postmarketing surveillance using large patients' registries could be helpful to improve the early detection of clinically relevant drug-drug interactions.

Effect of CYP2C9 genetic polymorphisms on the efficacy and pharmacokinetics of glimepiride in subjects with type 2 diabetes

Glimepiride, a sulfonylurea hypoglycemic agent, is metabolized by cytochrome P450 2C9 (CYP2C9) which is known to have genetic polymorphisms. To examine the effects of CYP2C9 genetic polymorphisms on the safety and efficacy of glimepiride in patients with type 2 diabetes, the responses to the glimepiride were measured in Japanese type 2 diabetic patients with the different CYP2C9 genotype. The reduction in the HbA(1c) was significantly larger (P<0.05) among the CYP2C9*1/*3 subjects than among the CYP2C9*1/*1 subjects. The long-term observations of 2 patients with a CYP2C9*1/*3 suggested that subjects with a CYP2C9*1/*3 respond well to glimepiride during the initial phase of treatment, but 1 patient have shown the weight gain over the long-term treatment. The pharmacokinetic study showed that the area under the concentration-time curve for glimepiride in the CYP2C9*1/*3 subjects was approximately 2.5-fold higher than that of the CYP2C9*1/*1 subjects. The intrinsic clearance of glimepiride by the CYP2C9*3 enzyme was lower than that by the CYP2C9*1 enzyme. These results suggested that the lower hydroxylation activity of glimepiride in the subject with type 2 diabetes and CYP2C9*1/*3 led to a marked elevation in the plasma concentrations of glimepiride and a stronger pharmacological effect of glimepiride.

Effects of glimepiride and glyburide on glucose counterregulation and recovery from hypoglycemia

Severe hypoglycemia, the most serious side effect of sulfonylurea therapy, has been reported to occur more frequently with glyburide than glimepiride. The present studies were undertaken to test the hypothesis that a differential effect on glucagon secretion may be involved. We performed hyperinsulinemic hypoglycemic (approximately 2.5 mmol/L) clamps in 16 healthy volunteers who received in randomized order placebo, glyburide (10 mg), and glimepiride (4 mg) just before beginning the insulin infusion and measured plasma glucagon, insulin, C-peptide, glucagon, epinephrine, cortisol, and growth hormone levels during the clamp and during a 3-hour recovery period after discontinuation of the insulin infusion. Neither sulfonylurea altered glucagon responses or those of other counterregulatory hormones (except cortisol) during the clamp. However, glyburide delayed plasma glucose recovery from hypoglycemia (plasma glucose at end of recovery period: control, 4.9 +/- 0.2 mmol/L; glyburide, 3.7 +/- 0.2 mmol/L; P = .0001; glimepiride, 4.5 +/- 0.2 mmol/L; P = .08). Despite lower plasma glucose levels, glyburide stimulated insulin secretion during this period (0.89 +/- 0.13 vs 1.47 +/- 0.15 pmol x kg(-1) x min(-1), control vs glyburide; P = .001), whereas glimepiride did not (P = .08). Short-term administration of glyburide or glimepiride did not alter glucagon responses during hypoglycemia. In contrast, during recovery from hypoglycemia, glyburide but not glimepiride inappropriately stimulates insulin secretion at low plasma glucose levels. This differential effect on insulin secretion may be an important factor in explaining why glyburide causes severe hypoglycemia more frequently than glimepiride.

Efficacy of glimepiride in Japanese type 2 diabetic subjects

We investigated the efficacy of glimepiride, a third-generation sulfonylurea (SU), in Japanese type 2 diabetic patients in whom glycemic control had been inadequate with a conventional SU, gliclazide or glibenclamide. A total of 172 Japanese type 2 diabetic patients (HbA1C > or = 7.0%), maintained on a conventional SU, were randomly assigned to the 3rd SU group (SU treatments switched to glimepiride) or the 2nd SU group (treatments not changed). The conventional SU was switched to the indicated doses of glimepiride (gliclazide 40 mg = glimepiride 1 mg, glibenclamide 2.5 mg = glimepiride 2 mg). After 6 months, glycemic control (HbA1C and fasting plasma glucose) had not changed significantly in either the 2nd or the 3rd SU group. The homeostasis assessment model of insulin resistance (HOMA-IR) in the 3rd SU group was decreased by more than 10% (p = 0.015), whereas no change was observed in the 2nd SU group. The triglyceride level was decreased by approximately 10% in the 3rd SU group, not a significant change (p = 0.080). Patients who had been treated with only SU, or treated with SU for a short time (less than 5 years), and who were also obese (BMI > or = 25) or had a high HOMA-IR (HOMA-IR > or = 3), showed significantly reduced insulin resistance. According to logistic regression analysis, high BMI ( > or = 25) was the only variable predicting that glimepiride would more effectively improve HbA1C than conventional SU treatment. In conclusion, switching conventional SUs to glimepiride reduced insulin resistance without improving glycemic control. A notable finding of this study is that glimepiride was more beneficial in obese than in non-obese Japanese type 2 diabetic patients.

Role of insulin secretagogues and insulin sensitizing agents in the prevention of cardiovascular disease in patients who have diabetes

In the absence of clinical trial evidence to compare the secretagogues with sensitizers, it is difficult to make recommendations about which class of drug is more important to prescribe for the prevention of cardiovascular disease in diabetes mellitus. Epidemiologic data supports insulin resistance as a major factor in cardiovascular disease through a variety of mechanisms. Because sensitizers improve insulin sensitivity and correct many of the vascular abnormalities that are associated with insulin resistance, it is tempting to suggest that they may be superior for this purpose. Conversely, meeting the goals that are recommended for glycemia also are important and achieving them may not be always possible with sensitizers, particularly in the later stages of the disease when insulin levels are not high,despite insulin resistance. In such situations,combination therapy may be needed with both types of drugs. No data are available on the cardiovascular effects of such combinations;some retrospective data suggest a possibility of increased events with the combination of sulfonylureas and metformin. Thus, further prospective studies in this area are necessary.

Investigation of structure-activity relationships in a series of glibenclamide analogues

In this study, the synthesis of 15 new glibenclamide analogues is described. The conformational trends of these analogues were investigated using Monte Carlo conformational analysis. The conformational analysis results resolved the discrepancy between previous molecular modelling simulations of glibenclamide and allowed rationalizing the effect of aqueous environment on the overall conformation. The 3D-QSAR study was carried out with respect to the compounds' ability to antagonize the [(3)H]-glibenclamide binging in rat cerebral cortex. Superimposition of the antagonists was performed using the conformations derived from atom-by-atom fit to the glibenclamide crystal structure and this alignment was used to develop CoMFA models. CoMFA provided a good predictability: number of PLS components = 2, q(2) = 0.876, R(2) = 0.921, SEE = 0.455 and F = 70. Best CoMFA models showed the steric and lipophilic properties as the major interacting forces whilst the electrostatic property contribution was a minor factor.

Effects of prolonged in vitro exposure to sulphonylureas on the function and survival of human islets

The direct effects of prolonged exposure to sulphonylureas on the function and survival of human islets are unknown. This study assessed the insulin content, glucose-stimulated insulin release, islet cell apoptosis, and mRNA expression of insulin and GLUT-1 in isolated human islets cultured in the presence of therapeutical concentrations of glimepiride (10 microM), glibenclamide (10 microM), or chlorpropamide (600 microM). Islets were prepared by collagenase digestion and density gradient purification from 18 multiorgan donors and were then exposed for 24 h to the different sulphonylureas. Insulin content decreased significantly following culture with any sulphonylurea compound. In response to an acute challenge with 3.3 and 16.7 mM glucose, insulin release from the control islets accounted for 1.9 +/- 0.5% and 4.9 +/- 1.7% of total insulin content (P<.01), respectively. Glucose responsiveness was preserved in islets precultured in the presence of glimepiride, whereas high glucose level did not elicit any significant increase of insulin secretion from islets preincubated with glibenclamide or chlorpropamide. These alterations were reverted by an additional 48-h incubation in drug-free conditions. The amount of apoptotic cells did not differ significantly among the experimental groups. Quantitative RT-PCR studies showed that, compared with the control islets, cells preincubated with glibenclamide or chlorpropamide had an increased expression of insulin mRNA, with no change in the expression of GLUT-1. In conclusion, prolonged exposure of human islets to different sulphonylureas causes different disturbances of islet cell function, with glimepiride showing milder effects, as compared with chlorpropamide and glibenclamide.

The role of glimepiride in the effective management of Type 2 diabetes

Type 2 diabetes mellitus, a disorder of impaired insulin secretion and insulin resistance, has reached epidemic proportions. The effective management of Type 2 diabetes is of vital concern to clinicians. The identification of high-risk individuals and lifestyle management can help control diabetes; however, most patients require pharmacologic intervention. The goals of pharmacologic therapy are to achieve adequate glycemic control while avoiding hypoglycemia and weight gain and to minimize the risk of future micro- and macrovascular complications. There are a number of available glucose-lowering agents from which to choose. This review focuses on the sulfonylureas, the first oral agents introduced for the management of Type 2 diabetes, which are effective, well-tolerated, and well-established drugs, Second-generation sulfonylureas are now widely used in the management of Type 2 diabetes. The most recent addition, glimepiride, can be used in combination with metformin, the thiazolidinediones, alpha-glucosidase inhibitors, and insulin. The unique properties of glimepiride may provide advantages over other currently available insulin secretagogues.

Change in patients' body weight after 12 months of treatment with glimepiride or glibenclamide in Type 2 diabetes: a multicentre retrospective cohort study

AIMS/HYPOTHESIS

Our study compared the effects of glimepiride or glibenclamide treatment on body weight over 12 months of treatment in patients with Type 2 diabetes in routine outpatient practice.

METHODS

This new retrospective study design used data from physicians in a restricted manner (retrolective). Data from case report forms from 520 patients from 91 randomly selected centres were assessed and covariance analysis performed.

RESULTS

The influence of practice and patient characteristics on treatment assignment was low, reflecting the design of randomised controlled trials. Mean weight loss and reduction in body mass index from baseline to study endpoint were greater with glimepiride than with glibenclamide (-2.04+/-3.99 kg vs -0.58+/-3.65 kg, p<0.001; -0.71+/-1.38 kg/m(2) vs -0.20+/-1.28 kg/m(2), p<0.001). Duration of treatment at baseline influenced treatment outcome, but propensity score, sex, age and fasting blood glucose at baseline did not. Both glimepiride and glibenclamide led to decreases in fasting blood glucose (-2.43+/-0.24 mmol/l vs -3.03+/-0.24 mmol/l; p<0.001 vs baseline) and HbA(1c) (-1.23+/-0.09% vs -1.26+/-0.09%; p<0.001 vs baseline). Both treatments were associated with a decrease in serum total cholesterol and low density lipoprotein cholesterol. Triglycerides were lower in the glibenclamide group and high density lipoprotein cholesterol was higher in the glimepiride group only.

CONCLUSIONS/INTERPRETATION

Initial treatment of Type 2 diabetes with glimepiride was associated with a significantly greater decrease in body weight and body mass index than treatment with glibenclamide, while providing equivalent glycaemic control.

Sulphonylurea action revisited: the post-cloning era

Hypoglycaemic agents such as sulphonylureas and the newer group of "glinides" stimulate insulin secretion by closing ATP-sensitive potassium (K(ATP)) channels in pancreatic beta cells, but have varying cross-reactivity with related channels in extrapancreatic tissues such as heart, vascular smooth and skeletal muscle. Experiments on the structure-function relationships of recombinant K(ATP) channels and the phenotypes of mice deficient in different K(ATP) channel subunits have provided important insights into the mechanisms underlying sulphonylurea selectivity, and the potential consequences of K(ATP) channel blockade outside the pancreatic beta cell. The different pharmacological properties of K(ATP) channels from beta cells compared with those from cardiac, smooth and skeletal muscle, are accounted for by the expression of alternative types of sulphonylurea receptor, with non-identical drug binding sites. The sulphonylureas and glinides are found to fall into two groups: one exhibiting selectivity for beta cell sulphonylurea receptors (SUR1), and the other blocking cardiovascular and skeletal muscle sulphonylurea receptors (SUR2) with potencies similar to their action on SUR1. In seeking potential side effects of K(ATP) channel inhibitors in humans, it is essential to take these drug differences into account, along with the probability (suggested by the studies on K(ATP) channel knockout mice) that the effects of extrapancreatic K(ATP) channel inhibition might be either subtle or rare. Further studies are still required before a final decision can be made on whether non-selective agents are appropriate for the therapy of Type 2 diabetes.

Effects of glimepiride on HbA(1c) and body weight in Type 2 diabetes: results of a 1.5-year follow-up study

Sulphonylureas are effective and well tolerated in patients with Type 2 diabetes, but may be associated with weight gain, and lack of compliance due to multiple daily dosing. This open, uncontrolled surveillance study examined the efficacy and safety of glimepiride, a new sulphonylurea, administered once daily in patients with Type 2 diabetes. A total of 1,770 patients were enrolled in the study, and 284 patients were selected for follow-up. Patients received 0.5 to >4 mg glimepiride once daily for 1.5 years. HbA(1c) was reduced from 8.4% at baseline to 7.1% after 4 months and 6.9% after 1 and 1.5 years (median intra-individual change from baseline: -1.4, -1.5, and -1.7%, respectively; P<0.0001). Treatment with glimepiride also resulted in significant and stable weight loss relative to baseline, with the exception of patients with a body mass index of <25 kg/m(2). Mean body weight was reduced from 79.8 kg at baseline to 77.9 kg after 4 months, 77.2 kg after 1 year, and 76.9 kg after 1.5 years (mean intra-individual change from baseline: -1.9 kg, P<0.0001; -2.9 kg, P<0.05; -3.0 kg, P<0.005, respectively). Therefore, once daily glimepiride provides effective glycaemic control, and may have advantages over other sulphonylureas, because it exhibits weight neutralizing/reducing effects in patients with Type 2 diabetes.

Characteristics and time course of severe glimepiride- versus glibenclamide-induced hypoglycaemia

OBJECTIVE

To compare the clinical characteristics and time course of severe hypoglycaemia (SH) on glimepiride and the reference drug glibenclamide.

METHODS

SH was defined as a symptomatic event requiring administration of i.v. glucose or of glucagon. Four hundred doctors working in acute care hospitals were randomly selected from the membership directory of the German Diabetes Association and sent a standardised questionnaire about sulphonylurea-induced SH that occurred between June 2001 and August 2002. Detailed data on history, medication, laboratory parameters, treatment and time course of the SH were analysed.

RESULTS

Altogether, 93 episodes of SH were registered, 37 on glimepiride and 56 on glibenclamide. The characteristics of the glimepiride- versus glibenclamide-induced SH were as follows: initial blood glucose 1.9+/-0.66 mmol/l versus 1.8+/-0.89 mmol/l, P=0.17; age 77+/-11.2 years versus 78+/-9.6 years, P=0.35; HbA1c 5.4+/-0.7% versus 5.2+/-0.9%, P=0.18; creatinine clearance 38+/-23 ml/min versus 54+/-32 ml/min, P=0.005; co-medication 6.2.+/-3 versus 3.6+/-3 preparations, P< 0.0001. Even very low doses of glimepiride (0.5 mg) and glibenclamide (0.88 mg) were associated with SH. Prolonged hypoglycaemia requiring more than 12 h i.v. glucose administration occurred in 8 of 37 of the glimepiride-treated subjects and 5 of 56 of those on glibenclamide. Prolonged hypoglycaemia necessitated infusion of 308+/-256 g (104-862 g) i.v. glucose over 43+/-16 h (24-64 h) in glimepiride-treated patients compared with 168+/-98 g (66-300 g) over 33+/-28 h (14-80 h) in glibenclamide-treated patients. Impaired renal function was present in 11 of 13 of all patients with prolonged hypoglycaemia and impaired liver function in 1 of 13.

CONCLUSION

In glimepiride- and glibenclamide-treated individuals with SH, no essential differences in the clinical characteristics or time course were shown; prolonged courses also occurred on glimepiride. Even in patients with only mild renal failure both preparations should be used with caution.

Glimepiride in type 2 diabetes mellitus: a review of the worldwide therapeutic experience

BACKGROUND

Sulfonylureas (SUs) have been used for many years as first-line therapy for patients with type 2 diabetes mellitus whose blood glucose levels have not been effectively controlled by diet and exercise alone. Glimepiride is a once-daily SU that was introduced in 1995. Since then, a considerable body of evidence has been amassed regarding its use in type 2 diabetes.

OBJECTIVE

This review provides a comprehensive summary of available data on the pharmacology, pharmacokinetics, efficacy, and safety profile of glimepiride in the treatment of type 2 diabetes. It also examines the use of glimepiride to achieve and maintain good glycemic control in patients with type 2 diabetes in current clinical practice.

METHODS

Relevant articles were identified through a search of MEDLINE for English-language studies published from 1990 to 2002. The search terms used were glimepiride, sulfonylureas, and type 2 diabetes mellitus. The manufacturer of glimepiride provided additional information.

RESULTS

Glimepiride differs from other SUs in a number of respects. In clinical studies, glimepiride was generally associated with a lower risk of hypoglycemia and less weight gain than other SUs. Results of other studies suggest that glimepiride can be used in older patients and those with renal compromise. There is evidence that glimepiride preserves myocardial preconditioning, a protective mechanism that limits damage in the event of an ischemic event. Glimepiride can be used in combination with other oral antidiabetic agents or insulin to optimize glycemic control.

CONCLUSION

Based on the evidence to date, glimepiride is an effective and well-tolerated once-daily antidiabetic drug and provides an important treatment option for the management of type 2 diabetes.

Impairment of myocardial protection in type 2 diabetic patients

Diabetic patients are more prone to develop postinfarction complications. It remained unclear whether diabetes mellitus- or sulfonylureas-associated changes of ATP-sensitive potassium (K(ATP)) channels, an integral player in ischemic preconditioning, are responsible for the increased mortality. The purpose of this study was to determine the impact of diabetes mellitus per se and different sulfonylurea administration on cardioprotective effects in diabetic patients undergoing coronary angioplasty. Myocardial ischemia after coronary angioplasty was evaluated in 20 nondiabetic and 23 diabetic patients chronically taking either glibenclamide or glimepiride. Nondiabetic patients treated with glimepiride significantly lowered the ischemic burden assessed by an ST-segment shift, chest pain score, and myocardial lactate extraction ratios compared with the glibenclamide-treated patients, implying that acute administration of glimepiride did not abolish cardioprotection. In the diabetic glibenclamide-treated group, the reduction in the ST-segment shift afforded by nicorandil in the first inflation (-58% vs. the first inflation in the glibenclamide group alone) was similar to that afforded by preconditioning (-59% during the second vs. the first inflation). In glimepiride-treated groups, the magnitude of attenuated lactate production was less in diabetes than that in nondiabetes at the second inflation, suggesting that diabetes mellitus per se plays a role in determining lactate production. Our results show that both diabetes mellitus and sulfonylureas can act in synergism to inhibit activation of K(ATP) channels in patients undergoing coronary angioplasty. The degree of inhibition assessed by metabolic and electrocardiographic parameters is less severe during treatment with glimepiride than with glibenclamide. Restitution of a preconditioning response in glimepiride-treated patients may be the potential beneficial mechanism.

The pathophysiologic basis of efficacy and clinical experience with the new oral antidiabetic agents

Type 2 diabetes results from the abnormal resistance of peripheral tissues to insulin and from the progressive insulin secretory failure of the pancreatic beta-cells. Treatment of type 2 diabetes has greatly improved due to the availability of new classes of oral antidiabetic drugs (OADs) and new insulin analogs. Three types of oral medications exert their antidiabetic action without directly stimulating insulin release: alpha-glucosidase inhibitors (e.g., acarbose) interfere with the digestion of dietary glucose precursors and the absorption of glucose; biguanides (e.g., metformin) inhibit hepatic gluconeogenesis, thereby lowering fasting blood glucose concentrations and increasing peripheral insulin sensitivity; and thiazolidinediones (e.g., rosiglitazone) improve the sensitivity of tissues to insulin-stimulated glucose disposal. In contrast, two classes of OADs stimulate insulin release from pancreatic beta-cells. Sulfonylureas (e.g., glyburide) have been used successfully for many years to treat type 2 diabetes, but their prolonged action may result in hypoglycemia. The third-generation sulfonylurea glimepiride is associated with a reduced risk of hypoglycemia and less weight gain than other sulfonylureas. Finally, the meglitinides (e.g., repaglinide) and D-phenylalanine derivatives (e.g., nateglinide) are powerful prandial insulin secretagogues. If the pancreatic beta-cells deteriorate to such an extent that insulin secretion is significantly impaired, treatment with additional exogenous insulin may be required.

Postprandial Hyperglycemia in Patients with Type 2 Diabetes Mellitus

The role of postprandial hyperglycemia (PPHG) in diabetes mellitus is being increasingly recognized. It is known that PPHG contributes to the increased risk of both micro- and macrovascular complications in patients with diabetes mellitus. This review looks at the clinical significance of PPHG and the currently available therapeutic modalities. The causes of PPHG are influenced by many factors which include a rapid flux of glucose from the gut, impaired insulin release, endogenous glucose production by the liver and peripheral insulin resistance. Knowledge of the pathophysiology of PPHG is essential when adopting treatment options to tackle the problem. Although most oral antihyperglycemic agents and insulins lower both fasting and postprandial blood glucose levels, drugs are now available which specifically act to control PPHG. These drugs may be classified based on the site of their action. alpha-Glucosidase inhibitors like acarbose and miglitol attenuate the rate of absorption of sucrose by acting on the luminal enzymes. Adverse effects of these agents are predominantly gastrointestinal. Newer insulin secretagogues have been developed which attempt to mimic the physiological release of insulin and thus ameliorate PPHG. These include third generation sulfonylureas like glimepiride and nonsulfonylurea secretagogues like repaglinide and nateglinide. Rapid-acting insulin analogs, the amino acid sequences of which have been altered such that they have a faster onset of action, help to specifically target PPHG. Pre-mixed formulations of the analogs have also been developed. Finally, drugs under development which hold promise in the management of patients with PPHG include pramlintide, an amylin analog, and glucagon-like peptide-1 and its analogs.

Lower incidence of severe hypoglycaemia in patients with type 2 diabetes treated with glimepiride versus glibenclamide

BACKGROUND

Severe hypoglycaemia is a potentially life-threatening condition. The aim of the present study was to compare the frequency of severe hypoglycaemia in patients with type 2 diabetes treated with glimepiride versus glibenclamide.

METHODS

This prospective, population-based, 4-year study examined the incidence of severe hypoglycaemia in a region of Germany with 200 000 inhabitants. The blood glucose of all 30 768 patients who attended the emergency department of the region's central hospital was determined to detect severe hypoglycaemia, which was defined by the requirement for intravenous glucose or glucagon injection and blood glucose value of <2.8 mmol/l. Additionally, 6631/7804 patients (85%) attended to by the emergency medical services received a blood glucose test at the emergency site. The regional prescribing frequency of both sulphonylureas was determined by an independent external institute.

RESULTS

Despite glimepiride being prescribed more frequently than glibenclamide (6976 vs 6789 person-years), glimepiride induced fewer episodes of hypoglycaemia (6 vs 38 episodes); one episode occurred with a combination of the two preparations. The incidence of severe hypoglycaemia was 0.86/1000 person-years for glimepiride and 5.6/1000 person-years for glibenclamide. The characteristics of the 45 patients who presented with sulphonylurea-associated hypoglycaemia were as follows: mean age 79 years (95% CI 75.2; 82.6); glycosylated haemoglobin 5.4% (95% CI 5.1; 5.7); impaired renal function in 62%.

CONCLUSIONS

In people with type 2 diabetes, glimepiride was associated with fewer episodes of severe hypoglycaemia than glibenclamide in routine clinical use. However, severe hypoglycaemia did occur with glimepiride and may be minimised if treatment targets are determined on an individual basis.

[Glimepiride (Amaryl): a review of its pharmacological and clinical profile]

In Type 2 diabetes, it is considered that the lowered insulin secretion and the lowered insulin sensitivity cause hyperglycemia. Sulfonylureas have strong blood-glucose lowering effect by stimulating insulin secretion and have been widely used in the treatment of Type 2 diabetes. However, the use of sulfonylurea has several problematic issues (weight gain, hypoglycemia, second failure and so on), which would due to stimulation of strong insulin secretion. Glimepiride, a new sulfonylurea, has a blood-glucose lowering effect as strong as those of existing sulfonylureas, but only induces mild insulin secretion. The sulfonylurea receptor has a weaker affinity for glimepiride than glibenclamide. The association and dissociation to the sulfonylurea receptor of glimepiride are faster than those of glibenclamide. Additionally, it is confirmed by basic studies that part of the glimepiride effect is attributable to improving insulin sensitivity. Glimepiride has already been used in more than 60 countries in the world. Outside of Japan, several clinical studies have demonstrated that glimepiride shows less hypoglycemia and no weight gain. Glimepiride is expected to be a new efficient agent for the treatment of Type 2 diabetes.

Glimepiride block of cloned beta-cell, cardiac and smooth muscle K(ATP) channels

1. We examined the effect of the sulphonylurea glimepiride on three types of recombinant ATP-sensitive potassium (K(ATP)) channels. 2. K(ATP) channels share a common pore-forming subunit, Kir6.2, which associates with different sulphonylurea receptor isoforms (SUR1 in beta-cells, SUR2A in heart and SUR2B in smooth muscle). 3. Kir6.2 was coexpressed with SUR1, SUR2A or SUR2B in Xenopus oocytes and macroscopic K(ATP) currents were recorded from giant inside-out membrane patches. Glimepiride was added to the intracellular membrane surface. 4. Glimepiride inhibited Kir6.2/SUR currents by interaction with two sites: a low-affinity site on Kir6.2 (IC(50)= approximately 400 microM) and a high-affinity site on SUR (IC(50)=3.0 nM for SUR1, 5.4 nM for SUR2A and 7.3 nM for SUR2B). The potency of glimepiride at the high-affinity site is close to that observed for glibenclamide (4 nM for SUR1, 27 nM for SUR2A), which has a similar structure. 5. Glimepiride inhibition of Kir6.2/SUR2A and Kir6.2/SUR2B currents, but not Kir6.2/SUR1 currents, reversed rapidly. 6. Our results indicate that glimepiride is a high-affinity sulphonylurea that does not select between the beta-cell, cardiac and smooth muscle types of recombinant K(ATP) channel, when measured in inside-out patches. High-affinity inhibition is mediated by interaction of the drug with the sulphonylurea receptor subunit of the channel.

Sustained enhancement of Ca(2+) influx by glibenclamide induces apoptosis in RINm5F cells

Cytosolic Ca(2+) elevations are known to be involved in triggering apoptosis in many tissues, but the effect of sustained enhancement of Ca(2+) influx on apoptosis in beta cells remains unknown. We have found that the viability of RINm5F cells is decreased dose-dependently by continuous exposure to glibenclamide at concentrations from 10(-7) to 10(-4) M, and that this effect is partially ameliorated by pretreatment with cycloheximide. Electrophoresis of the cells exposed to glibenclamide revealed ladder-like fragmentation characteristic of apoptosis, and which also is suppressed by cycloheximide pretreatment. By using terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling (TUNEL) staining, we detected increased DNA fragmentation in the nuclei of the cells exposed to glibenclamide, and staining with Hoechst 33342 and propidium iodide showed a dose-dependent increase in the number of cells with the chromatin condensation and fragmentation in their nuclei that is characteristic of apoptosis. The effects of glibenclamide on cell viability and apoptotic cell death were partially inhibited by treatment with Ca(2+) channel blocker, and by reducing the extracellular Ca(2+) concentration during glibenclamide exposure, suggesting that they may be derived from increased Ca(2+) influx. Furthermore, only the percentage of apoptotic cells, and not that of necrotic cells, increased with the increasing intracellular Ca(2+) concentration during glibenclamide exposure. In conclusion, we have demonstrated that the sustained enhancement of Ca(2+) influx caused by glibenclamide exposure can induce apoptotic cell death in a pure beta cell line.

[Present status in the treatment of type 2 diabetes mellitus. Insulin-secreting agents]

The functional defect of the pancreatic beta cell represents one of the main therapeutic targets in type 2 diabetes mellitus. Among the currently available oral antidiabetic drugs, only hypoglycaemic sulfonylureas exhibit beta cell stimulating properties. However, their use has some limits, particularly those related to the risk of hypoglycaemia and the frequent secondary therapeutic failure. These drugs have largely contributed to the knowledge of the mechanisms of insulin secretion. Besides some galenic modifications of existing sulfonylureas and the development of new drugs of this family with original properties, like glimepiride, the research is essentially focused on drugs derived from the non sulfonylurea moiety of some sulfonylureas, particularly the meglitinide family, which will probably be available for the clinician in the near future. These drugs act however grossly by the same mechanism than sulfonylureas, even if their binding site on a protein coupled with the ATP sensitive K channel appears different. Among the other possible approaches suggested by the theoretical data concerning the mechanisms of insulin secretion, GLP-1 derivatives probably represent good candidates, if stable analogues are developed.

Comparison of the efficacy of glibenclamide and glimepiride in reperfusion-induced arrhythmias in rats

The effect of glibenclamide and glimepiride, two orally active antidiabetic sulphonylurea derivatives, was investigated on the development of reperfusion-induced arrhythmias and it was compared to their blood glucose lowering action. Arrhythmias were produced by reperfusion following 6 min coronary artery ligation in anaesthetised rats. Glimepiride pretreatment (0.001-0.01-0.1-5.0 mg/kg i.p., 30 min before coronary occlusion) significantly decreased the incidence of irreversible ventricular fibrillation and increased the survival rate during reperfusion (64%, 61%, 60%, and 67% vs. 27% in controls). Glibenclamide produced similar effect (81% survival) only in a dose of 5 mg/kg, while smaller doses were ineffective. The minimal hypoglycaemic dose and the dose required to inhibit significantly the oral glucose loading-induced hyperglycaemia were similar (1 and 0.1 mg/kg, respectively) after glibenclamide and glimepiride. It is concluded that although the blood glucose lowering potency of glibenclamide and glimepiride is rather similar, glimepiride appears to be more potent than glibenclamide in preventing reperfusion-induced cardiac arrhythmias.

Glimepiride: role of a new sulfonylurea in the treatment of type 2 diabetes mellitus

OBJECTIVE

To review the clinical pharmacology data regarding the sulfonylurea glimepiride, and to summarize the clinical trials of glimepiride efficacy and safety alone and in combination with insulin for the treatment of type 2 diabetes mellitus.

DATA SOURCES

A MEDLINE database search (English language, January 1985-April 1997) was performed to identify relevant published articles, including reviews and abstracts; the manufacturer (Hoechst Marion Roussel, Kansas City, MO) provided unpublished data.

STUDY SELECTION

Pharmacology information was taken from representative original research articles. Eight clinical studies were selected for analysis on the basis of large enrollment, appropriate study design, and publication of results.

DATA EXTRACTION

All clinical trials, published and unpublished, were reviewed.

DATA SYNTHESIS

Glimepiride is a sulfonylurea that is pharmacologically distinct from other sulfonylureas because of differences in receptor-binding properties and potentially selective effects on ATP-sensitive K+ channels. The pharmacokinetic and pharmacodynamic profile of glimepiride makes it suitable for once-daily dosing. The safety and efficacy of glimepiride have been confirmed in studies involving more than 5000 patients with type 2 diabetes. In one study, once-daily doses of 1-8 mg reduced fasting plasma glucose from baseline by 43-74 mg/dL more than did placebo (p < 0.001), and hemoglobin (Hb) A1C values decreased by 1.2-1.9% more than with placebo (p < 0.001). Two-thirds of patients achieved tight control (i.e., HbA1C < or = 7.2%). Glimepiride was as effective as second-generation sulfonylureas. The most common adverse events were dizziness and headache, but no single adverse event occurred in more than 2% of patients.

CONCLUSIONS

Glimepiride appears to be a useful option for patients with type 2 diabetes not controlled by diet and exercise and who want to achieve tight glucose control. Glimepiride can be used alone, in combination with other antihyperglycemic agents, or in patients with secondary sulfonylurea failure, as an adjunct to insulin therapy.

A placebo-controlled, randomized study of glimepiride in patients with type 2 diabetes mellitus for whom diet therapy is unsuccessful

This multicenter, randomized, placebo-controlled study of glimepiride, a new oral sulfonylurea, was conducted in patients with type 2 diabetes for whom dietary treatment was unsuccessful (fasting plasma glucose [FPG] = 151-300 mg/dL) during a 1-week screening period. Patients were randomized to receive glimepiride (n = 123) or placebo (n = 126) once daily for a 10-week dose-titration period, then maintained on an individually determined optimal dose (1-8 mg of glimepiride or placebo) for 12 weeks. Glimepiride lowered FPG by 46 mg/dL, hemoglobin A1C (HbA1C) by 1.4%, and 2-hour postprandial glucose by 72 mg/dL more than placebo. Glimepiride improved postprandial insulin and C-peptide responses without producing clinically meaningful increases in fasting insulin or C-peptide levels. Good glycemic control (HbA1C < or = 7.2%) was achieved by 69% of the patients taking glimepiride versus 32% of those taking placebo. The overall incidence of adverse events was similar in both groups. No clinically noteworthy abnormal laboratory values or hypoglycemia (blood glucose < 60 mg/dL) occurred. Glimepiride is safe and effective for treatment of patients with type 2 diabetes for whom diet therapy is unsuccessful.

Glimepiride. A review of its use in the management of type 2 diabetes mellitus

Glimepiride is a sulphonylurea agent that stimulates insulin release from pancreatic beta-cells and may act via extrapancreatic mechanisms. It is administered once daily to patients with type 2 (non-insulin-dependent) diabetes mellitus in whom glycaemia is not controlled by diet and exercise alone, and may be combined with insulin in patients with secondary sulphonylurea failure. The greatest blood glucose lowering effects of glimepiride occur in the first 4 hours after the dose. Glimepiride has fewer and less severe effects on cardiovascular variables than glibenclamide (glyburide). Pharmacokinetics are mainly unaltered in elderly patients or those with renal or liver disease. Few drug interactions with glimepiride have been documented. In patients with type 2 diabetes, glimepiride has an effective dosage range of 0.5 to 8 mg/day, although there is little difference in efficacy between dosages of 4 and 8 mg/day. Glimepiride was similar in efficacy to glibenclamide and glipizide in 1-year studies. However, glimepiride appears to reduce blood glucose more rapidly than glipizide over the first few weeks of treatment. Glimepiride and gliclazide were compared in patients with good glycaemic control at baseline in a 14-week study that noted no differences between their effects. Glimepiride plus insulin was as effective as insulin plus placebo in helping patients with secondary sulphonylurea failure to reach a fasting blood glucose target level of < or = 7.8 mmol/L, although lower insulin dosages and more rapid effects on glycaemia were seen with glimepiride. Although glimepiride monotherapy was generally well tolerated, hypoglycaemia occurred in 10 to 20% of patients treated for < or = 1 year and > or = 50% of patients receiving concomitant insulin for 6 months. Pooled clinical trial data suggest that glimepiride may have a lower incidence of hypoglycaemia than glibenclamide, particularly in the first month of treatment. Dosage is usually started at 1 mg/day, titrated to glycaemic control at 1- to 2-week intervals to a usual dosage range of 1 to 4 mg/day (maximum 6 mg/day in the UK or 8 mg/day in the US).

CONCLUSIONS

Glimepiride is a conveniently administered alternative to other sulphonylureas in patients with type 2 diabetes mellitus not well controlled by diet alone. Its possible tolerability advantages and use in combination with other oral antidiabetic drugs require further study. Glimepiride is also reported to reduce exogenous insulin requirements in patients with secondary sulphonylurea failure when administered in combination with insulin.

Interaction of sulphonylurea derivatives with vascular ATP-sensitive potassium channels in humans

Cardiovascular adenosine-5'-triphosphate-sensitive potassium (KATP) channels have been reported to play an important role in endogenous cardioprotective mechanisms. Sulphonylurea derivatives can inhibit these cardioprotective mechanisms in animal models. We investigated whether therapeutic concentrations of sulphonylurea derivatives can block vascular KATP channels in humans. The forearm vasodilator responses to administration of the specific KATP channel opener diazoxide into the brachial artery of healthy male volunteers were recorded by venous occlusion plethysmography. This procedure was repeated with concomitant intraarterial infusion of:1) the sulphonylurea derivative glibenclamide (0.33 or 3.3 micrograms. min-1. dl-1, both n = 12), 2) the new sulphonylurea derivative glimepiride (2.5 micrograms.min-1. dl-1, n = 12) or 3) placebo (n = 12). The effects of glibenclamide on the vasodilator responses to sodium nitroprusside were also studied (n = 12). Glibenclamide significantly inhibited the diazoxide-induced increase in forearm blood flow ratio (ANOVA with repeated measures: p < 0.01). During the highest diazoxide dose this ratio (mean +/- SEM) was lowered from 892 +/- 165 to 449 +/- 105%, and from 1044 +/- 248 to 663 +/- 114% by low- and high-dose glibenclamide, respectively. In contrast, neither glimepiride nor placebo attenuate diazoxide-induced vasodilation. Furthermore, glibenclamide did not affect nitroprusside-induced vasodilation. We conclude that therapeutic concentrations of the classical sulphonylurea derivative glibenclamide result in significant blockade of vascular KATP channels in humans. The newly developed glimepiride seems to be devoid of these properties.

Haemodynamic and other effects of sulphonylurea drugs on the heart

Antidiabetic sulphonylureas have attracted a great deal of interest in experimental cardiology to evaluate the role of ATP-sensitive potassium channels in the cardiovascular system. It is well established that KATP channels are present in cardiac cells and also in vascular smooth muscle cells and are implicated in the regulation of myocardial and vascular function. It follows that drugs which open, or inhibit the opening of these channels, might profoundly modify cardiovascular function both under physiological and pathophysiological conditions. This paper reviews the evidence for the role of KATP channels in the cardiovascular system and discusses how the different generations of sulphonylurea drugs interfere with cardiac function. We will particularly concentrate on the haemodynamic effects of different sulphonylureas and shortly discuss how these drugs modify ischaemia-reperfusion arrhythmias.

Effects of glimepiride on insulin and glucagon release from isolated rat pancreas at different glucose concentrations

The effects of glimepiride, the newest sulphonylureic compound, on pancreatic insulin and glucagon secretion were studied using the classical, isolated, perfused rat pancrease model. The influence of four different environmental glucose conditions (during a glycaemic stimulus with glucose increasing from 5 to 8.33 mM and at stable 0, 5 and 2.22 mM glucose levels) on the effects of glimepiride was also assessed. At a pharmacological concentration glimepiride strongly stimulated beta-cell activity, producing a characteristic biphasic insulin release with a sharp first-phase secretory peak, followed by a prolonged and sustained second phase. Environmental glucose concentrations markedly influenced the extent, but not the pattern of glimepiride-induced insulin secretion, as hormone release dropped significantly when the glucose level was reduced. Glimepiride failed to influence alpha-cell activity at any of the environmental glycaemic levels.

Stimulation of glucose utilization in 3T3 adipocytes and rat diaphragm in vitro by the sulphonylureas, glimepiride and glibenclamide, is correlated with modulations of the cAMP regulatory cascade

The long-term hypoglycemic activity of sulphonylurea drugs has been attributed, in part at least, to the stimulation of glucose utilization in extra-pancreatic tissues. The novel sulphonylurea, glimepiride, gives rise to a longer lasting reduction in the blood sugar level in dogs and rabbits compared to glibenclamide (Geisen K, Drug Res 38: 1120-1130, 1988). This cannot be explained adequately by elevated plasma insulin levels. This study investigated whether this prolonged hypoglycemic phase was based on the drug's abilities to stimulate glucose utilization and affect the underlying regulatory mechanisms in insulin-sensitive cells in vitro. It was found that in the absence of added insulin, glimepiride and glibenclamide (1-50 microM) stimulated lipogenesis (3T3 adipocytes) and glycogenesis (isolated rat diaphragm) approximately 4.5- and 2.5-fold, respectively, and reduced the isoproterenol-stimulated lipolysis (rat adipocytes) up to 40-60%. The increased glucose utilization was correlated with a 3-4-fold higher 2-deoxyglucose transport rate and amount of GLUT4 at the plasma membrane, as well as with increased activities of key metabolic enzymes (glycerol-3-phosphate acyltransferase, glycogen synthase) within the same concentration range. Furthermore, the low Km cAMP-specific phosphodiesterase was activated 1.8-fold, whereas the cytosolic cAMP level and protein kinase A activity ratios were significantly lowered after incubation of isoproterenol-stimulated rat adipocytes with the sulphonylureas. In many of the aspects studied the novel sulphonylurea, glimepride, exhibited slightly lower ED50-values than glibenclamide. This study demonstrates correlations existing between drug-induced stimulation of glucose transport/metabolism and cAMP degradation/protein kinase A inhibition as well as between the relative efficiencies of glimepiride and glibenclamide in inducing these extra-pancreatic processes. Therefore, it is suggested that the stimulation of glucose utilization by sulphonylureas is mediated by a decrease of cAMP-dependent phosphorylation of GLUT4 and glucose metabolizing enzymes. The therapeutic relevance of extra-pancreatic effects of sulphonylureas, in general, and of the differences between glimepiride and glibenclamide as observed in vitro in this work, in particular, remain to be elucidated.

Differential interaction of glimepiride and glibenclamide with the beta-cell sulfonylurea receptor. II. Photoaffinity labeling of a 65 kDa protein by [3H]glimepiride

Glimepiride is a novel sulfonylurea for the treatment of type II-diabetic patients exhibiting different receptor binding kinetics to beta-cell membranes with 8-9-fold higher koff rate and 2.5-3-fold higher kon rate compared to glibenclamide (see accompanying paper (Müller, G. et al. (1994) Biochim. Biophys. Acta 1191, 267-277)). To elucidate the molecular basis for this differential behaviour of glimepiride and glibenclamide, direct photoaffinity labeling studies using beta-cell tumor membranes were performed. [3H]Glimepiride was specifically incorporated into a membrane polypeptide of M(r) = 65,000 under conditions, which led to predominant labeling of a 140 kDa protein by [3H]glibenclamide (Kramer, W. et al. (1988) FEBS Lett. 229, 355-359). Labeling of the 140 kDa protein by [3H]glibenclamide was inhibited by unlabeled glimepiride and, vice versa, glibenclamide inhibited labeling of the 65 kDa protein by [3H]glimepiride. The 65 kDa protein was also specifically photolabeled by the sulfonylurea [125I]35623, whereas an 4-azidobenzoyl derivative of glibenclamide, N3-[3H]33055, exclusively labeled a 33 kDa protein. Competitive Scatchard analysis of [3H]glimepiride-binding and [3H]glibenclamide-binding to RINm5F cell membranes using glibenclamide and glimepiride, respectively, as heterologous displacing compounds yielded non-linear plots. These findings may be explained by cooperative interactions between the 140 and 65 kDa sulfonylurea-binding proteins. The possibility that sulfonylureas of different structure have different access to the 140 and 65 kDa receptor proteins due to the beta-cell membrane barrier was investigated by photoaffinity labeling of solubilized beta-cell membrane proteins. Interestingly, solubilization of beta-cell tumor membranes led to a shift of specific [3H]glibenclamide binding from the 140 kDa to the 65 kDa binding protein, exclusively, and to an increased labeling of the 65 kDa protein by [3H]glimepiride. The labeling of a unique protein is in agreement with similar Kd values measured for both sulfonylureas upon solubilization of beta-cell tumor and RINm5F cell membranes (see accompanying paper). Furthermore, competitive Scatchard plots of [3H]glimepiride binding to solubilized RINm5F cell membrane proteins in the presence of glibenclamide and vice versa approximate linearity suggesting loss of cooperativity between the 140 kDa glibenclamide-binding and 65 kDa glimepiride-binding proteins upon solubilization. The physiological significance of the differential interaction of glimepiride and glibenclamide with different binding proteins was also substantiated by photoaffinity labeling of RINm5F cells leading to labeling of a 140 kDa protein by [3H]glibenclamide and of a 65 kDa protein by [3H]glimepiride.(ABSTRACT TRUNCATED AT 400 WORDS)