Gliclazide. An update of its pharmacological properties and therapeutic efficacy in non-insulin-dependent diabetes mellitus

Cyclodextrin complexes of salts of acidic drugs. Thermodynamic properties, structural features, and pharmaceutical applications

The objective of this mini-review is to summarize the findings concerning the physicochemical properties and the pharmaceutical applications of acidic drugs whose performances have been modified by simultaneous complexation with cyclodextrins and salt formation. Particular attention is paid to the approaches undertaken for increasing the solubility of the drugs by proper choice of the type of counterion analogously to what has been reported for complexes of basic drugs in the presence of hydroxy acids.

Gliclazide modified release: its place in the therapeutic armamentarium

The constraints of intensive multifactorial management of type 2 diabetes dictate a need for effective, well-tolerated agents with simple administration regimens. Sulfonylureas remain the most frequently used agents, and represent a rational approach when consideration is given to the pathophysiology of this common condition. Trials of gliclazide modified release in varied populations have yielded very acceptable clinical results that support its first-line use in type 2 diabetes, including obese, elderly, and mild-to-moderate renal insufficient patients. The simplicity of its dose regimen and its efficacy and tolerance profile may significantly contribute to improving compliance.

Diamicron MR once daily is effective and well tolerated in type 2 diabetes: a double-blind, randomized, multinational study

In a double-blind, multicenter, multinational study, the long-term efficacy and safety of Diamicron(R)MR, a new gliclazide formulation taken once daily at lower dose (30-120 mg/day) was compared with Diamicron(R) (80-320 mg/day) taken twice daily in type 2 diabetic outpatients. After a 2-week run-in period, 800 patients with poor blood glucose control were randomized to Diamicron(R)MR (n=401) or Diamicron(R) (n=399). After a 4-month titration period, the efficacy and safety of Diamicron(R)MR was compared with Diamicron(R) over a 6-month fixed-dose treatment period. The ability to switch from Diamicron(R) to Diamicron(R)MR was then assessed during an additional 2-month follow-up period. Equivalence between treatment with Diamicron(R)MR and Diamicron(R) was compared by a non-inferiority test; the limit of equivalence was set at 0.5% for HbA(1c) and 1 mmol/l for fasting plasma glucose (FPG). The treatment groups were comparable at baseline. After 10 months of treatment, Diamicron(R)MR was as efficient as Diamicron(R) in controlling blood glucose, with a mean end point difference in HbA(1c) of -0.08 (0. 08)%, significantly lower than the equivalence limit (p<0.001). Similar results were obtained for FPG.The safety of Diamicron(R)MR and Diamicron(R) was equally high. The incidence of hypoglycemia was particularly low (0.2 hypoglycemia/100 patient months) in the elderly population, which represented almost 40% of the included patients. This study demonstrates that 30 to 120 mg of Diamicron(R)MR taken once daily is at least as efficient as 80 to 320 mg of Diamicron(R) taken in divided doses with respect to HbA(1c) and FPG levels, with a similar safety profile.

Correction of glycosylated oxyhemoglobin-induced impairment of endothelium-dependent vasodilatation by gliclazide

We have investigated whether gliclazide, a second-generation sulfonylurea hypoglycemic agent, interferes with the impairment of endothelium-dependent nitric-oxide-mediated relaxation produced by 14%-glycosylated human oxyhemoglobin (GHHb). For comparative purposes, other agents, like glibenclamide, aminoguanidine, ascorbic acid or superoxide dismutase (SOD), were also tested. GHHb (10 nM) caused a reduction in endothelium-dependent relaxation induced by acetylcholine (1 nM to 10 microM) in both isolated aortic segments and mesenteric microvessels from normoglycemic nondiabetic rats. Preincubation of the vessels with gliclazide (100 nM to 10 microM) prevented the impairment of endothelial relaxation, the threshold concentration of gliclazide being 300 nM. In addition, 10 microM gliclazide also prevented the reduction by 10 nM GHHb of the relaxation induced by exogenous nitric oxide (NO, 10 nM to 100 microM). Determination of superoxide anion release measured by the reduction in ferricytochrome c indicated that GHHb produced significant amounts of these free radicals that were concentration-dependently inhibited by gliclazide. The impairment of endothelium-mediated responses was also prevented by 100 U/ml SOD or 10 microM ascorbic acid, but not by 10 microM glibenclamide or 100 microM aminoguanidine. We conclude that gliclazide can reduce the impairment of nitric-oxide-mediated endothelium-dependent relaxation produced by GHHb. This reduction is likely related to the antioxidant properties of the drug, a mechanism suggested by these studies which demonstrate the inactivation of superoxide anions produced by the glycosylated protein by gliclazide.

In vitro and in vivo antioxidant properties of gliclazide

Diabetes is a state of increased oxidant stress and there is evidence that oxidation may play a role in the genesis of complications. Gliclazide, a sulfonylurea hypoglycemic drug, has been shown to possess free radical scavenging properties. This study examined the effects of in vitro supplementation with gliclazide and other sulfonylureas as on low-density lipoprotein (LDL) oxidation and the total plasma antioxidant capacity (TPAC). In a separate study, the effects of 10 months of oral gliclazide therapy on oxidative parameters were assessed in 44 type 2 diabetic patients. Gliclazide, but not glibenclamide, glimepiride, glipizide or tolbutamide, inhibited LDL oxidation and enhanced TPAC. With the addition of 1 microM gliclazide, oxidation lag time increased from 53.6+/-2.6 to 113.6+/-5.1 min (p<0.001), and TPAC increased from 1. 09+/-0.11 to 1.23+/-0.11 mM (p<0.01). Administration of either modified release or standard gliclazide to type 2 diabetic patients resulted in a fall in 8-isoprostanes, a marker of lipid oxidation, and an increase in the antioxidant parameters TPAC, SOD and thiols. These studies show that gliclazide possesses antioxidant properties that produce measurable clinical effects at therapeutic doses.

Prevention of endothelial dysfunction in streptozotocin-induced diabetic rats by gliclazide treatment

The aim of the present work was to analyze whether the oral hypoglycemic drug gliclazide affects diabetic endothelial dysfunction in streptozotocin-induced diabetic rats. Gliclazide was compared with glibenclamide, ascorbic acid, and aminoguanidine. An insulin-dependent model of diabetes was selected to exclude insulin-releasing effects of the drugs. Both in isolated aortic segments and mesenteric microvessels, endothelium-dependent relaxation evoked by acetylcholine (ACh, 1 nM to 10 microM) was significantly reduced in vessels from diabetic animals. This impairment was reversed when the segments were previously incubated with 100 U/ml superoxide dismutase. When streptozotocin-induced diabetic rats were orally treated from the time of diabetes induction with gliclazide (10 mg/kg) or ascorbic acid (250 mg/kg), ACh-induced endothelium-dependent relaxation was well preserved both in aortic segments and mesenteric microvessels. In addition, the impaired vasodilatation to exogenous nitric oxide (NO) in aortic segments was also improved in gliclazide-treated diabetic rats. On the other hand, oral treatment with glibenclamide (1 and 10 mg/kg) or aminoguanidine (250 mg/kg) did not produce significant improvements in diabetic endothelial dysfunction. We conclude that gliclazide reverses the endothelial dysfunction associated with diabetes. This effect appears to be due not to the metabolic actions of the drug but rather to its antioxidant properties, as it can be mimicked by other antioxidants. We propose that the mechanism involved is the inactivation of reactive oxygen species, which are increased in diabetes probably as a result of increased early protein glycosylation products, such as glycosylated hemoglobin (HbA(1c)). These effects of gliclazide are not shared by other oral hypoglycemic agent such as glibenclamide, or by blockade of advanced glycosylation end product (AGE) generation with aminoguanidine.

Pharmacokinetics and pharmacodynamics of gliclazide in Caucasians and Australian Aborigines with type 2 diabetes

AIMS

Gliclazide pharmacokinetics and pharmacodynamics were assessed in 9 Caucasians and 10 Australian Aborigines with uncomplicated type 2 diabetes.

METHODS

Subjects were on a stable dose of 80 mg gliclazide twice daily, took 160 mg on the morning of study and had a standard breakfast. No further gliclazide was given over the next 48 h. Regular blood samples were drawn for serum glucose, insulin and gliclazide assay. Gliclazide was measured using h.p.l.c. Noncompartmental analysis was used to describe primary data. A multicompartment model incorporating entero-hepatic recirculation was fitted to group mean serum gliclazide profiles.

RESULTS

The Caucasians were older than the Aborigines (mean +/- s.d. age 53.4 +/- 12.2 vs 40.3 +/- 6.9 years, P < 0.05) but had similar diabetes duration, body mass index and glycated haemoglobin. Noncompartmental analysis revealed no between-group differences in gliclazide kinetics. Post-breakfast serum glucose and insulin responses were also similar apart from a longer time to maximum concentration (tmax) for glucose amongst the Aborigines (2.6 +/- 0.4 vs 2.2 +/- 0. 3 h in Caucasians; P = 0.024). Gliclazide tmax exhibited a skewed unimodal distribution and was not associated with gliclazide maximum concentration, or glucose or insulin responses. Most patients had a serum gliclazide profile suggestive of enterohepatic recirculation and/or biphasic absorption. Model-derived estimates of the extent of putative enterohepatic recirculation were 30% and 20% of dose in Caucasians and Aborigines, respectively.

CONCLUSIONS

Gliclazide is equally effective in Caucasian and Aboriginal diabetic patients. The pharmacokinetics of oral gliclazide appear more complex than previously thought. Gliclazide pharmacodynamics are unrelated to rate and extent of absorption, consistent with a threshold concentration for hypoglycaemic effect.

Pharmacological interference of vascular smooth muscle cell hypertrophy induced by glycosylated human oxyhaemoglobin

Nonenzymatically glycosylated human oxyhaemoglobin induces vascular smooth muscle cell hypertrophy by releasing reactive oxygen species. We analysed the ability of drugs with antihypertrophic properties for the vascular wall and/or antioxidant activity, such as captopril, losartan, and nifedipine, or gliclazide, carvedilol, and ascorbic acid, to interfere with 10 nM glycosylated human oxyhaemoglobin-induced increase in vascular smooth muscle cell size (118+/-0.5% of basal). Vascular smooth muscle cell hypertrophy was abolished concentration-dependently, with pD(2) values over a 100-fold interval: 6.4+/-0.3, 7.7+/-0.4, 7.3+/-0.4, 7.4+/-0.6, 8. 8+/-0.2, and 9.0+/-0.2 for captopril, losartan, nifedipine, ascorbic acid, carvedilol and gliclazide, respectively. Drugs with powerful antioxidant properties, especially carvedilol and gliclazide, are particularly effective in preventing glycosylated human oxyhaemoglobin-induced vascular smooth muscle cell hypertrophy.

The use of sulphonylureas in the elderly

Type 2 diabetes mellitus is a heterogeneous disorder characterised by defects in insulin secretion as well as reduced insulin action. During aging, glucose intolerance will gradually develop, and this is manifested primarily by an increase in the postprandial blood glucose response while fasting blood glucose levels are often less elevated. Abnormal beta-cell secretion of insulin is a main feature of this. Treatment of elderly patients with type 2 diabetes mellitus focuses on reduction of (hyperglycaemic) complaints and prevention of the development or progression of secondary complications. Although regular physical activity and dietary measures, aiming at bodyweight normalisation, are the cornerstones of therapy, pharmacological treatment with oral blood glucose lowering-agents often proves necessary to control the hyperglycaemia. In the United Kingdom Prospective Diabetes Study (UKPDS) it was clearly shown that patients with type 2 diabetes mellitus who were intensively treated with oral blood glucose-lowering agents or insulin developed less microvascular complications. The question whether achievement of strict metabolic control is also of benefit in elderly patients, is still unanswered. Sulphonylureas are drugs which stimulate insulin secretion by enhancing the release of insulin from the pancreatic beta-cells without an effect on insulin synthesis. They are frequently used in the treatment of type 2 diabetes mellitus, and several preparations are available. In general, there are no major differences in effectiveness between the various sulphonylureas. Long term treatment with sulphonylureas will decrease fasting and postprandial plasma glucose levels by 3 to 5 mmol/L, and glycosylated haemoglobin by 20%. However, after its initial decline, plasma glucose level will often go up slightly during the following months to years. Sulphonylureas are usually well tolerated. Hypoglycaemia is the most frequently occurring adverse effect, which may be very serious and damaging in the elderly. It has been associated primarily with long-acting sulphonylureas, like chlorpropamide and glibenclamide (glyburide). Hypoglycaemic episodes may trigger serious events like myocardial infarction or stroke. Therefore, shorter-acting compounds like tolbutamide and gliclazide have been relatively well tolerated and appear to be the best choice to treat elderly patients. It is advisable to start with a low dose and increase the dose, when needed, in small steps. The efficacy of sulphonylureas is much greater when they are taken before a meal. Because of the fact that type 2 diabetes mellitus is a progressive disease, and residual beta-cell function decreases with time, insulin therapy may ultimately be warranted in a significant number of patients.

Review of management of type 2 diabetes mellitus

BACKGROUND

Commonly used drugs for type 2 diabetes are not ideal. The sulphonylureas, especially potent and long-acting agents such as glibenclamide, can induce hypoglycaemia, while metformin carries the risk of lactic acidosis.

AIM

To review the management of type 2 diabetes at the major teaching hospital in Tasmania, Australia, principally to determine the extent of use of glibenclamide and metformin in the elderly and patients where published contraindications are present.

METHODS

A retrospective review of the medical records for 150 consecutive patients with type 2 diabetes admitted to the hospital in mid-1997, was performed. An extensive range of demographic and clinical variables was recorded for each patient. These included the duration of type 2 diabetes, the presence of other medical conditions, medication history, presence of any contraindications to the use of metformin or sulphonylureas, biochemical measures of diabetic control, and the presence of any diabetic complications.

RESULTS

The mean (+/-SD) age of the 150 patients included in the study was 70.1+/-11.8 years. The mean body mass index was 28.7+/-6.2 kg/m2 and the mean recent HbA1c level was 86+/-21%; only 24.7% of patients had a HbA1c level of 7% or lower. Of the 45 patients using glibenclamide, 40 (88.9%) had one or more risk factors for hypoglycaemia: over 65 years of age, renal impairment, or cognitive impairment and living alone. The study also found an extensive use of metformin in patients with contraindications and at highest risk of developing lactic acidosis. Sixty-six out of 70 patients (94%) using metformin had at least one contraindication according to the manufacturer's prescribing information, 57% of patients had two or three contraindications and 14% of patients had more than three contraindications. More than 20% of the patients had a renal function below published exclusion criteria.

CONCLUSIONS

There was evidence of over-utilization of metformin and glibenclamide in type 2 diabetes patients most at risk of adverse reactions. Insulin therapy could be a safer and more effective management strategy in many of these patients.

Gliclazide inhibits diabetic neuropathy irrespective of blood glucose levels in streptozotocin-induced diabetic rats

N-acetylcysteine and pentoxifylline, free radical scavengers and inhibitors of tumor necrosis factor-alpha (TNF-alpha) production, inhibit the development of peripheral neuropathy in streptozotocin (STZ)-induced diabetic rats. This study was designed to elucidate the effect of gliclazide, an oral hypoglycemic sulfonylurea, on diabetic neuropathy, because it has been indicated to be a free radical scavenger and TNF-alpha inhibitor. Rats were fed with powder chow mixed with gliclazide or glibenclamide as a control ad libitum. Blood glucose levels and body weight were remarkably higher and lower in diabetic than in nondiabetic rats, respectively, while gliclazide and glibenclamide had no effect on these in both diabetic and nondiabetic rats throughout a 24-week experiment. Serum lipoperoxide levels and lipopolysaccharide (LPS)-induced serum TNF-alpha activities were significantly increased in diabetic rats, whereas these were significantly inhibited in gliclazide-treated rats. Motor nerve conduction velocity (MNCV) of the tibial nerve significantly slowed in diabetic rats compared with nondiabetic rats. On the other hand, the slowed MNCV was significantly inhibited in gliclazide-treated diabetic rats after 16 experimental weeks. Morphometric analysis showed that gliclazide prevented decreased myelinated fiber area (P < .05), increased fiber density (P < .001), and decreased axon/myelin ratio (P < .05) in diabetic rats. Glibenclamide treatment did not affect serum lipoperoxide, TNF-alpha, MNCV, or nerve morphology in this experiment. These results indicate that gliclazide has a beneficial effect on peripheral neuropathy in STZ-induced diabetic rats, irrespective of blood glucose levels.

Accelerated oral absorption of gliclazide in human subjects from a soft gelatin capsule containing a PEG 400 suspension of gliclazide

Whether a rapid elevation of serum gliclazide concentration in human subjects can be achieved through an acceleration of dissolution of gliclazide from a formulation was examined. A soft gelatin capsule containing PEG 400, PEG 4000, Tween 20 and glycerin was prepared as a formulation that may accelerate dissolution of gliclazide. The in vitro dissolution of gliclazide at pH 7.2 was identical for the soft capsule and conventional tablets, Diamicron and Diberin. However, at pH 1, 2 and 4.0 the dissolution from the soft capsule was more rapid compared to the tablets. When bioavailability parameters were compared following oral administration of the soft capsule and Diamicron to 16 healthy Korean male subjects, the parameters representing the amount of adsorption (i.e. the area under the serum gliclazide concentration vs. time curve up to 24 h, AUC24, and the peak serum concentration Cmax) were not statistically different for both formulations. However, the time required to reach the peak (Tmax) was significantly shorter for the soft capsule than for the Diamicron. Our results, therefore, indicate that a rapid elevation of serum gliclazide concentration following oral administration of a formulation can be achieved by accelerating the in vitro dissolution of gliclazide from the formulation into the acidic buffers. Thus, the rate of gastrointestinal absorption of gliclazide appears to be dependent on its in vivo dissolution rate in gastric fluid. A soft capsule containing a PEG 400 suspension of gliclazide appears to be an appropriate formulation for accelerating the dissolution.

Microvascular permeability with sulfonylureas in normal and diabetic hamsters

The hamster cheek pouch is an experimental model in which quantitative studies of macromolecular permeability can be made by direct observation of extravasated fluorescein isothiocyanate (FITC)-dextran (leaks). The advantage of this model is that simultaneous light and fluorescent-light microscopy observations can be performed with instantaneous correlations between the site of FITC-dextran extravasation and the vessel morphology. The aims of our study were to compare, using the cheek pouch preparation, the effects of two sulfonylureas, gliclazide and glibenclamide, on the macromolecular permeability increase induced by histamine using control (normoglycemic) hamsters. In these studies, FITC-labeled dextran 150,000 daltons was administered intravenously and quantified by UV-light microscopy, and the drugs used were applied topically at therapeutic concentrations. Gliclazide and glibenclamide dose-dependently decreased the macromolecular permeability increase induced by histamine. This effect of gliclazide could be blocked by nifedipine (Ca2+ channel blocker) and not by diazoxide (K+ channel opener), whereas for glibenclamide it could be blocked by diazoxide and not by nifedipine. To better characterize the antioxidant capacity of gliclazide and glibenclamide, their effect on the macromolecular permeability increase induced by ischemia/reperfusion was also compared with the effect of vitamin C in diabetic hamsters (glycemia > 240 mg/dL). Total ischemia of the preparation was obtained with a cuff placed around the neck of the everted pouch. Diabetes was induced by three intraperitoneal injections of streptozotocin 50 mg/kg/d in 3 days. In diabetic hamsters during ischemia/reperfusion, gliclazide was more effective in inhibiting the macromolecular permeability increase than glibenclamide (136.0 +/- 5.8 leaks/cm2 for placebo; 68.0 +/- 2.9 for 1.2 x 10(-6) mol/L gliclazide; 55.3 +/- 3.5 for 1.2 x 10(-5) mol/L gliclazide; 89.2 +/- 5.7 for 8 x 10(-8) mol/L glibenclamide; 107.0 +/- 3.8 for 8 x 10(-7) mol/L glibenclamide; 56.7 +/- 3.4 for 10(-6) mol/L vitamin C; and 20.5 +/- 0.6 for 10(-5) mol/L vitamin C). Our results suggest that (1) the inhibition of the permeability increase induced by histamine elicited by gliclazide may be mediated by Ca2+ channels, while that of glibenclamide may be mediated by K+ channels, and (2) gliclazide appears to have an antioxidant capacity in ischemia/reperfusion injury similar to that of 10(-6) mol/L vitamin C. Improvement in the microcirculation was independent of the hypoglycemic properties of the drug.

Sulfonylureas

Sulfonylureas have been available for the treatment of non-insulin-dependent diabetes mellitus (NIDDM) since the 1950s. With the introduction of new oral agents, there is a tendency to discount the value of sulfonylurea therapy. Sulfonylureas have the advantage of multiple formulations, low costs, minimal side effects, and demonstrated efficacy in controlling hyperglycemia. The major disadvantage of sulfonylureas is secondary failure, which may occur with all oral agents as part of the progression of NIDDM. Sulfonylureas should continue to play an important role in the treatment of NIDDM.

Nuclear magnetic resonance investigations of the inclusion complexation of gliclazide with beta-cyclodextrin

The formation of the gliclazide-beta-cyclodextrin (GL-beta-CD) inclusion compound has been studied in the liquid state by phase solubility techniques and by 1H and 13C NMR spectroscopy. From the initial straight portion of the solubility curve (Bs type), the value of the apparent stability constant (Kc) was calculated as 1094 M(-1). The nuclear magnetic resonance studies confirm that GL yields a complex with beta-CD in aqueous medium, which is mainly due to the penetration of the azabicyclooctyl group of GL into the cavity of beta-CD. The study of the monodimensional nuclear Overhauser effect (NOE) of the H3 proton of CD has shown that the tolyl group also interacts with CD, but to a lesser extent than the azabicyclooctyl moiety. Finally, the application of the continous variation technique confirmed the 1:2 drug:CD stoichiometry of the complex.

Interference by gliclazide in the glucose oxidase/peroxidase method for glucose assay

Gliclazide interferes with the glucose determination using the glucose oxidase/peroxidase (EC 1.1.3.4/1.11.1.7) (GOD-PERID) method utilizing 2,2-azino-di-(3-ethyl-benzothiazoline-6-sulphonic acid) (ABTS) as the oxygen acceptor chromogen. There was an essentially linear relationship between the concentrations of gliclazide and decreasing glucose readings. One mu mol/1 of gliclazide in samples leads to an apparent loss of about 2.5 mu mol/l of glucose. However, gliclazide did not interfere with the glucose determination using the hexokinase/glucose-6-phosphate dehydrogenase method. This interference in the GOD-PERID method for glucose assay can occur in the in vitro experimental samples and cause underestimation of the glucose values. It is suggested that careful attention should be paid to the limited applicability of the GOD-PERID method for glucose assay.

Problems and pitfalls of sulphonylurea therapy in older patients

The prevalence of non-insulin-dependent diabetes mellitus (type II) increases with age, so that approximately half of all known patients in English-speaking countries are over 65 years of age. There is no reason to believe that the criteria for blood glucose control should be any less stringent for elderly patients unless they have a limited life expectancy. Sulphonylurea drugs remain an effective means of achieving blood glucose control after failure of dietary therapy alone in older patients. However, changes in normal metabolism of drugs with age and the development of other pathologies in elderly patients make it important that these drugs are prescribed with care. Severe symptomatic hypoglycaemia is the most serious adverse effect of sulphonylurea drugs and this becomes progressively more likely with increasing age, depending primarily on the substantial reduction of renal function with normal aging. Other adverse effects are much less commonly of clinical importance. To minimise the risk of hypoglycaemia, it is important that patients receive closely supervised dietary management with education about their disease for at least 3 months before sulphonylurea drugs are prescribed. In elderly patients a short-acting agent with no active metabolites should be used. As patients become older, those receiving long-acting agents can be changed to short-acting agents before problems arise. If blood glucose control appears satisfactory on treatment, then symptoms of hypoglycaemia should be sought. If control is poor, then the criteria for introduction of insulin, with appropriate education, do not differ from those in younger patients.