Sulphonylurea antidiabetic drugs. An update of their clinical pharmacology and rational therapeutic use

Comparison of long-term effects of metformin on longevity between people with type 2 diabetes and matched non-diabetic controls

BACKGROUND

Metformin, a medication for type 2 diabetes, has been linked to many non-diabetes health benefits including increasing healthy lifespan. Previous work has only examined the benefits of metformin over periods of less than ten years, which may not be long enough to capture the true effect of this medication on longevity.

METHODS

We searched medical records for Wales, UK, using the Secure Anonymised Information Linkage dataset for type 2 diabetes patients treated with metformin (N = 129,140) and sulphonylurea (N = 68,563). Non-diabetic controls were matched on sex, age, smoking, and history of cancer and cardiovascular disease. Survival analysis was performed to examine survival time after first treatment, using a range of simulated study periods.

FINDINGS

Using the full twenty-year period, we found that type 2 diabetes patients treated with metformin had shorter survival time than matched controls, as did sulphonylurea patients. Metformin patients had better survival than sulphonylurea patients, controlling for age. Within the first three years, metformin therapy showed a benefit over matched controls, but this reversed after five years of treatment.

INTERPRETATION

While metformin does appear to confer benefits to longevity in the short term, these initial benefits are outweighed by the effects of type 2 diabetes when patients are observed over a period of up to twenty years. Longer study periods are therefore recommended for studying longevity and healthy lifespan.

EVIDENCE BEFORE THIS STUDY

Work examining the non-diabetes outcomes of metformin therapy has suggested that there metformin has a beneficial effect on longevity and healthy lifespan. Both clinical trials and observational studies broadly support this hypothesis, but tend to be limited in the length of time over which they can study patients or participants.

ADDED VALUE OF THIS STUDY

By using medical records we are able to study individuals with Type 2 diabetes over a period of two decades. We are also able to account for the effects of cancer, cardiovascular disease, hypertension, deprivation, and smoking on longevity and survival time following treatment.

IMPLICATIONS OF ALL THE AVAILABLE EVIDENCE

We confirm that there is an initial benefit to longevity of metformin therapy, but this benefit does not outweigh the negative effect on longevity of diabetes. Therefore, we suggest that longer study periods are required for inference to be made about longevity in future research.

ABCC9/SUR2 in the brain: Implications for hippocampal sclerosis of aging and a potential therapeutic target

The ABCC9 gene and its polypeptide product, SUR2, are increasingly implicated in human neurologic disease, including prevalent diseases of the aged brain. SUR2 proteins are a component of the ATP-sensitive potassium ("KATP") channel, a metabolic sensor for stress and/or hypoxia that has been shown to change in aging. The KATP channel also helps regulate the neurovascular unit. Most brain cell types express SUR2, including neurons, astrocytes, oligodendrocytes, microglia, vascular smooth muscle, pericytes, and endothelial cells. Thus it is not surprising that ABCC9 gene variants are associated with risk for human brain diseases. For example, Cantu syndrome is a result of ABCC9 mutations; we discuss neurologic manifestations of this genetic syndrome. More common brain disorders linked to ABCC9 gene variants include hippocampal sclerosis of aging (HS-Aging), sleep disorders, and depression. HS-Aging is a prevalent neurological disease with pathologic features of both neurodegenerative (aberrant TDP-43) and cerebrovascular (arteriolosclerosis) disease. As to potential therapeutic intervention, the human pharmacopeia features both SUR2 agonists and antagonists, so ABCC9/SUR2 may provide a "druggable target", relevant perhaps to both HS-Aging and Alzheimer's disease. We conclude that more work is required to better understand the roles of ABCC9/SUR2 in the human brain during health and disease conditions.

Sulfonylurea use before stroke does not influence outcome

BACKGROUND AND PURPOSE

Sulfonylureas block nonselective cation channels and lower serum glucose and are neuroprotective in animal models of ischemic stroke. Human data on sulfonylureas in acute stroke are sparse and conflicting. We aimed to measure the potential neuroprotective effect of prestroke sulfonylurea use in diabetic patients.

METHODS

We analyzed data from a prospective cohort of individuals with diabetes mellitus (DM) enrolled in nonreperfusion ischemic stroke trials within Virtual International Stroke Trials Archive (VISTA) comprising 1050 patients, 298 with sulfonylurea use before stroke onset. The primary outcome measures were baseline National Institutes of Health Stroke Scale score and 90-day modified Rankin Scale score.

RESULTS

Compared with patients on no DM medications, those with sulfonylurea use before stroke onset presented with less severe stroke (OR, 0.69; 95% CI, 0.53 to 0.89) but had similar modified Rankin Scale scores at 90 days (OR, 0.95; 95% CI, 0.74 to 1.23). Compared with those on other DM agents, there was no difference in initial stroke severity (OR, 1.04; 95% CI, 0.73 to 1.48) nor modified Rankin Scale score at 90 days (OR, 1.00; 95% CI, 0.71 to 1.40). Compared with those using any DM medication, patients not on any treatment experienced higher initial National Institutes of Health Stroke Scale scores (OR, 1.48; 95% CI, 1.18 to 1.86) and were marginally more likely to have poor outcomes (modified Rankin Scale score >2) at 90 days (OR, 1.31; 95% CI, 0.97 to 1.77).

CONCLUSIONS

Sulfonylurea use before stroke onset did not affect stroke severity or long-term functional outcome compared with other DM treatments. This finding casts doubt on the use of sulfonylureas for prophylactic neuroprotection. Furthermore, patients not using any medication for DM appear to have more severe strokes and worse outcomes.

Conformational polymorphism in sulfonylurea drugs: electronic structure analysis

Quantum chemical calculations have been performed using HF, B3LYP, and MP2 methods on the model sulfonylurea PhSO(2)NHC(=O)NHMe to understand the conformational and tautomeric preferences. The results indicate that a conformer with intramolecular hydrogen bond SLU-1 (hitherto not considered) is more stable than the conformer SLU-2 (which is generally considered) for sulfonylureas. The energy difference between these two conformers is about 4 kcal/mol in the gas phase; however, the energy differences between the two rotamers become negligible in the solvent phase. Iminol tautomeric forms of sulfonylurea (which were also not studied until now) are only about 5-6 kcal/mol higher in energy as per both gas-phase and solvent-phase analyses, indicating easy accessibility of tautomeric states in sulfonylureas. Quantum chemical analysis has also been carried out on the possible dimeric structures of these three important isomers of sulfonylurea, and correlations have been made to the known crystal structures of polymorphic states of sulfonylurea drugs.

Effect of glimepiride and nateglinide on serum insulin and glucose concentration in healthy cats

Glimepiride and nateglinide are two common oral hypoglycemic agents currently being used with humans suffering from Type 2 diabetes mellitus. Neither drug has been tested with cats thus far and it is currently unknown whether either of these drugs exert any effect in cats or not. The objective of this study was to determine the effect of glimepiride and nateglinide on glucose and insulin responses in healthy control cats, in order to determine their potential use in diabetic cats. The intravenous glucose tolerance tests was carried out since it is an excellent test for evaluating pancreatic beta-cell function for insulin secretion. Alterations in the insulin secretion pattern can be perceived as the earliest sign of beta-cell dysfunction in many species, including cats. Nateglinide demonstrated a quick action/short duration type effect with serum glucose nadiring and insulin response peaking at 60 and 20 minutes, respectively. Alternatively, glimepiride is medium-to-long acting with serum glucose nadiring and insulin response peaking at 180 minutes and 60 minutes, respectively. Nateglinide's potency was evident allowing it to induce a 1.5-2 higher preliminary insulin peak (3.7 +/- 1.1 pg/ml) than glimepiride's (2.5 +/- 0.1 pg/ml), albeit only for a short period of time. Because glimepiride and nateglinide have a shared mode of action, no significant differences in overall glucose AUC(0-360 min) (24,435 +/- 2,940 versus 24,782 +/- 2,354 mg min/dl) and insulin AUC(0-360 min) (410 +/- 192 versus 460 +/- 159) in healthy control cats were observed. These findings may provide useful information when choosing a hypoglycemic drug suited for the treatment of diabetic cats depending on the degree of diabetes mellitus the cat is suffering from.

Differential effects of oral hypoglycemic agents on glucose control and cardiovascular risk

Cardiovascular disease (CVD) burden remains the predominant cause of mortality and morbidity in the United States and in most of the developed world. The ongoing twin epidemics of obesity and type 2 diabetes mellitus provide a groundswell source for sustaining this trend for the foreseeable future (increasing the prevalence of CVD by 2-4 times), unless radical changes are made in public health policy. Oral hypoglycemic agents (OHAs) remain a mainstay for management of type 2 diabetes in most practice settings. Although these agents are primarily prescribed to achieve better glycemic control, it is important to evaluate what effects they have on cardiovascular risk and whether there are significant differences in effects among the different OHAs. This review presents the available data on the effects of the various OHAs on cardiovascular risk surrogates and actual events in retrospective and prospective study design settings.

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.

The role of sulphonylureas in the management of type 2 diabetes mellitus

The sulphonylureas act by triggering insulin release from the pancreatic beta cell. A specific site on the adenosine triphosphate (ATP)-sensitive potassium channels is occupied by sulphonylureas leading to closure of the potassium channels and subsequent opening of calcium channels. This results in exocytosis of insulin. The meglitinides are not sulphonylureas but also occupy the sulphonylurea receptor unit coupled to the ATP-sensitive potassium channel. Glibenclamide (glyburide), gliclazide, glipizide and glimepiride are the primary sulphonylureas in current clinical use for type 2 diabetes mellitus. Glibenclamide has a higher frequency of hypoglycaemia than the other agents. With long-term use, there is a progressive decrease in the effectiveness of sulphonylureas. This loss of effect is the result of a reduction in insulin-producing capacity by the pancreatic beta cell and is also seen with other antihyperglycaemic agents. The major adverse effect of sulphonylureas is hypoglycaemia. There is a theoretical concern that sulphonylureas may affect cardiac potassium channels resulting in a diminished response to ischaemia. There are now many choices for initial therapy of type 2 diabetes in addition to sulphonylureas. Metformin and thiazolidinediones affect insulin sensitivity by independent mechanisms. Disaccharidase inhibitors reduce rapid carbohydrate absorption. No single agent appears capable of achieving target glucose levels in the majority of patients with type 2 diabetes. Combinations of agents are successful in lowering glycosylated haemoglobin levels more than with a single agent. Sulphonylureas are particularly beneficial when combined with agents such as metformin that decrease insulin resistance. Sulphonylureas can also be given with a basal insulin injection to provide enhanced endogenous insulin secretion after meals. Sulphonylureas will continue to be used both primarily and as part of combined therapy for most patients with type 2 diabetes.

5-aryl thiazolidine-2,4-diones: discovery of PPAR dual alpha/gamma agonists as antidiabetic agents

A novel series of 5-aryl thiazolidine-2,4-diones based dual PPARalpha/gamma agonists was identified. A number of highly potent and orally bioavailable analogues were synthesized. Efficacy study results of some of these analogues in the db/db mice model of type 2 diabetes showed them superior to rosiglitazone in correcting hyperglycemia and hypertriglyceridemia.

Are hypoglycaemia and other adverse effects similar among sulphonylureas?

This review provides an updated overview of the adverse effects of sulphonylureas and identifies factors associated with variation in adverse effect rates among sulphonylureas published by different studies. A search of Medline, Embase, Current Contents and Cochrane Library was conducted to identify all papers related to sulphonylureas and adverse effects published from 1950-2001. The reference lists of all relevant papers were also searched for additional articles. The frequency of sulphonylurea-induced hypoglycaemia varied from 1.8-59%. Severe hypoglycaemia due to sulphonylurea use has been reported from 1.9-3.5%. Variation in hypoglycaemia rates may be due to differences in definitions, methods to detect and to collect information, patient characteristics, patient knowledge of the condition, threshold for symptoms, and activity level during hypoglycaemia. Other adverse effects associated with sulphonylurea use include bodyweight gain, gastrointestinal distress, disulphiram-like syndrome, dermatological reactions, haematological changes, ocular problems, and the syndrome of inappropriate secretion of antidiuretic hormone. Bodyweight gain has been reported to vary from 1.7-4.8 kg, according to the United Kingdom Prospective Diabetes Study (UKPDS-33). Controversy exists regarding cardiovascular adverse effects, but the consensus is to exercise caution in the use of these drugs as first-line therapy for patients with diabetes mellitus and coronary artery disease. The benefits of sulphonylurea treatment should be weighed against the risks associated with them. More work in this area is needed to homogenise the definition of hypoglycaemia, to get consensus on the methods for detection and data collection, as well as to further patient and physician education.

Pharmacokinetics and pharmacodynamics of glyburide/metformin tablets (Glucovance) versus equivalent doses of glyburide and metformin in patients with type 2 diabetes

OBJECTIVE

To compare the effects of two different formulations of glibenclamide (glyburide) combined with metformin on postprandial glucose excursions, and to assess their pharmacokinetics. The formulations were a combination glibenclamide/metformin tablet (Glucovance; controlled-particle-size glibenclamide and metformin) versus glibenclamide (Micronase) and metformin (Glucophage) coadministered separately.

DESIGN

A randomised, double-blind, two-way crossover study in which patients with type 2 diabetes received either glibenclamide/metformin 2.5/500mg tablets or glibenclamide 2.5mg with metformin 500mg twice daily for 14 days. After a 2-week washout, patients were crossed over to the other treatment for 14 days. Patients consumed standardised meals on the days when pharmacokinetic and pharmacodynamic evaluations were performed.

PARTICIPANTS

Forty patients with type 2 diabetes were enrolled; 37 were randomised (18 men, 19 women) and 35 completed the study. Mean age was 58 years; mean body mass index was 31 kg/m(2). The baseline glycated haemoglobin (HbA(1c)) was 9.3% for both treatment groups.

MAIN OUTCOME MEASURE

Two-hour postprandial glucose excursion (PPGE) was used to assess postprandial glucose dynamics.

RESULTS

Treatment with glibenclamide/metformin resulted in a significantly smaller mean PPGE than was attained by treatment with glibenclamide plus metformin, according to measurements taken after the day 14 afternoon standardised meal (89.5 vs 117.4 mg/dl, p = 0.011). The mean glibenclamide peak concentration (C(max)) was significantly greater (approximately 16%) after glibenclamide/metformin treatment on both days 1 and 14. Glibenclamide/metformin treatment was associated with a 2-fold greater area under the concentration-time curve to 3 hours for glibenclamide (AUC(3)) [p < 0.001], although the AUC over the administration interval was equivalent for both formulations.

CONCLUSION

In patients with type 2 diabetes, glibenclamide/metformin resulted in lower PPGE, suggesting that the higher glibenclamide AUC(3) observed with this formulation may contribute to better postprandial glycaemic control than is attained by glibenclamide plus metformin separately.

Clinical pharmacokinetics and pharmacodynamics of repaglinide

Repaglinide is a novel, fast-acting prandial oral hypoglycaemic agent developed for the treatment of patients with type 2 diabetes whose disease cannot be controlled by diet and exercise alone. Although repaglinide binds to the sulphonylurea binding sites on pancreatic beta-cells and has a similar mechanism of action, repaglinide exhibits distinct pharmacological properties compared with these agents. Following administration, repaglinide is absorbed rapidly and has a fast onset of dose-dependent blood-glucose lowering effect. The drug is eliminated rapidly via the biliary route, without accumulation in the plasma after multiple doses. Repaglinide is well tolerated in patients with type 2 diabetes, including elderly patients and patients with hepatic or renal impairment. The pharmacokinetic profile of repaglinide and the improvements in post-prandial hyperglycaemia and overall glycaemic control make repaglinide suitable for administration preprandially, with the opportunity for flexible meal arrangements, including skipped meals, without the risk of hypoglycaemia.

Bioequivalence evaluation of two brands of gliclazide 80 mg tablets (Glyzide & Diamicron)--in healthy human volunteers

A randomized, two-way, crossover, bioequivalence study in 24 fasting, healthy, male volunteers was conducted to compare two brands of gliclazide 80 mg tablets, Glyzide (Julphar, UAE) as test and Diamicron (Servier Industries, France) as reference product. The study was performed at the International Pharmaceutical Research Centre (IPRC), in joint venture with Speciality Hospital, Amman, Jordan. The drug was administered with 240 ml of 20% glucose solution after a 10 h overnight fasting. After dosing, serial blood samples were collected for a period of 48 h. Plasma harvested from blood was analyzed for gliclazide by validated HPLC method. Various pharmacokinetic parameters including AUC(0-t), AUC(0- proportional, variant), C(max), T(max), T(1/2), and elimination rate constant were determined from plasma concentrations of both formulations. Statistical modules (ANOVA and 90% confidence intervals) were applied to AUC(0-t), AUC(0- proportional, variant), and C(max) for bioequivalence evaluation of the two brands which revealed no significant difference between them, and 90% CI fell within US FDA accepted bioequivalence range of 80-125%. Based on these statistical inferences, Glyzide was judged bioequivalent to Diamicron.

Repaglinide improves blood glucose control in sulphonylurea-naive type 2 diabetes

The prandial glucose regulator repaglinide has a rapid onset of action, a short half-life and is metabolised mainly by the liver. Here we report the findings of a 10-week, double-blind, parallel, placebo controlled, randomised trial with repaglinide in 25 diet-treated, sulphonylurea-naïve patients with Type 2 diabetes. Repaglinide was titrated, based on capillary blood glucose, from 0.5 mg to a maximum of 4 mg, preprandially with breakfast and dinner. After 10 weeks, repaglinide was associated with a decrease in HbA(1c) of 2.3%Hb relative to the placebo group (P=0.018). This reflected a 30% decrease within the repaglinide group from a mean HbA(1c) of 7.0 to 4.9%Hb (P<0.002). Repaglinide was also associated with a decrease in fructosamine, by 0.88 mmol/l, relative to placebo (P<0.001), with a 20% decrease (from 3.80 to 3.04 mmol/l) within the repaglinide group (P<0.001). Fasting and postprandial blood glucose concentrations decreased in association with repaglinide by 3.6 and 6.4 mmol/l, respectively, relative to placebo (P<0.001 in each case). Within the repaglinide group fasting and postprandial blood glucose decreased by 3.9 and 6.2 mmol/l, respectively (P<0.001 in each case). The number of patients reporting hypoglycaemia in the repaglinide group was similar to placebo (15 vs. 20, respectively; NS). Test meal assessments confirmed that repaglinide effectively controls glucose levels by stimulating mealtime insulin secretion. Fasting serum insulin concentration was not raised compared to baseline or placebo during repaglinide therapy, albeit that fasting glucose levels were decreased by repaglinide. Twice-daily meal-related insulin secretagogue therapy with repaglinide, a new short and rapid-acting prandial glucose regulator, is capable of improving all measures of glycaemic control without increased hypoglycaemia or fasting hyperinsulinaemia.

Isolation of antidiabetic components from white-skinned sweet potato (Ipomoea batatas L.)

We have already reported that white-skinned sweet potato (Ipomoea batatas L.) (WSSP) shows antidiabetic activity in streptozotocin (STZ) induced diabetic rats and genetically diabetic models (yellow KK, db/db mice and Zucker fatty rats). In this study, isolation and purification of the antidiabetic component of WSSP were attempted. Almost all antidiabetic activity was found in the cortex of WSSP. The fractionation of the antidiabetic component in the WSSP cortex was done by the following methods: dialysis of the water extract, 85% ethanol precipitation, 15% trichloroacetic acid (TCA) treatment, butyl-, phenyl-hydrophobic column chromatography, and ultrafiltration treatment. The antidiabetic component was not eliminated during dialysis and was soluble in 85% ethanol and 15% TCA, but it passed through a filter that allows the passage of substances of a molescular weight of 30,000. The uniformity of this isolated active component was analyzed using HPLC. A single peak was seen with three different columns (C8 reverse-phase column, anion exchange QA column, and gel filtration column (GFC)), indicating that the component is a uniform substance. The molecular weight of this antidiabetic component was estimated to be 22,000 by GFC analysis. This active component was presumed to be an acidic glycoprotein because it contained protein and sugar and was adsorbed onto the QA column at pH 7.0.

Characteristics of pancreatic beta-cell secretion in Type 2 diabetic patients treated with gliclazide and glibenclamide

The aim of the present cross-over study was to compare the beta-cell response to gliclazide and glibenclamide administered orally during and following a hyperglycaemic clamp in sulphonylurea treated Type 2 diabetes. Nine patients (6 males), aged 61.4 (S.D. 6.9) years with a body mass index of 27.5 (3.1) kg m(-2) and HbA(1c) at baseline of 7.2 (0.9)% were included. Eight healthy control subjects underwent the same tests. Patients received 80-240 mg gliclazide or 5-15 mg glibenclamide for 6 weeks. Thirty minutes after administration of 160 mg of gliclazide or 10 mg of glibenclamide a 1-h hyperglycaemic clamp (11.0 mmol l(-1)) was begun, and followed by a 3.5-h observation period. Nadir blood glucose levels were 4.2 (1.0), 4.3 (1.2) and 3.4 (1.0) mmol l(-1) for glibenclamide gliclazide and controls, respectively (both P=0.07 vs. controls). Glucose levels decreased slowly and linearly in people with diabetes and reached nadirs after 204 (8) and 198 (18) min, respectively, after cessation of glucose infusion, while in controls, glucose levels declined steeply to a nadir at 98 (47) min (P<0.003 vs. both drugs). No first phase insulin secretion peak was observed in people with diabetes. Insulin levels remained elevated during the 3-h observation period in SU treated patients but, in control subjects decreased to baseline values within 2 h of the clamp. The proinsulin to C-peptide ratio increased during the observation period. In conclusion, the effects of glibenclamide and gliclazide on insulin secretion are very similar in patients with Type 2 diabetes who are in moderate glycaemic control, with a slow rise to lower amplitude, poor responsiveness to falling glucose levels, and raised proinsulin to C-peptide ratio.

A rational approach to drug therapy of type 2 diabetes mellitus

Several new pharmacological agents have recently been developed to optimise the management of type 2 (non-insulin-dependent) diabetes mellitus. The aim of this article is to briefly review the various therapeutic agents available for management of patients with type 2 diabetes mellitus and to suggest a potential approach to drug selection. There are three general therapeutic modalities relevant to diabetes care. The first modality is lifestyle adjustments aimed at improving endogenous insulin sensitivity or insulin effect. This can be achieved by increased physical activity and bodyweight reduction with diet and behavioural modification, and the use of pharmacological agents or surgery. This first modality is not discussed in depth in this article. The second modality involves increasing insulin availability by the administration of exogenous insulin, insulin analogues, sulphonylureas and the new insulin secretagogue, repaglinide. The most frequently encountered adverse effect of these agents is hypoglycaemia. Bodyweight gain can also be a concern, especially in patients who are obese. The association between hyperinsulinaemia and premature atherosclerosis is still a debatable question. The third modality consists of agents such as biguanides and thiazolidinediones which enhance insulin sensitivity, or agents that decrease insulin requirements like the alpha-glucosidase inhibitors. Type 2 diabetes mellitus is a heterogeneous disease with multiple underlying pathophysiological processes. Therapy should be individualised based on the degree of hyperglycaemia, hyperinsulinaemia or insulin deficiency. In addition, several factors have to be considered when prescribing a specific therapeutic agent. These factors include efficacy, safety, affordability and ease of administration.

Pharmacotherapy of type 2 diabetes mellitus

OBJECTIVE

To review the drug treatments and some of the popular, nontraditional remedies now available for type 2 diabetes mellitus, as well as selected investigational agents; to describe each medication's place in the overall approach to treatment.

DATA SOURCES

English-language journals, abstracts, review articles, and newspaper accounts.

DATA SYNTHESIS

In the past five years, there has been tremendous progress in the pharmacotherapy of diabetes, particularly type 2 diabetes. Several new agents have entered the clinical arena, and many more are in the late stages of investigation leading to approval. Sulfonylureas stimulate the production and release of insulin; these drugs must be used in patients with an intact pancreas. The meglitinides are nonsulfonylurea agents that are also insulin secretagogues. Unlike the sulfonylureas, repaglinide appears to require the presence of glucose to close the adenosine triphosphate-sensitive potassium channels and induce calcium influx. Metformin reduces hepatic glucose production in some patients and increases peripheral glucose utilization, but its use is hampered by a high percentage of adverse reactions. Disaccharidase inhibitors effectively compensate for the defective early-phase insulin release by slowing the production of sugars from carbohydrates. Thiazolidinediones appear to activate peroxisome proliferator-activated receptor gamma, which is involved in the metabolism of lipids. Short-acting insulin and the role of weight-loss agents are also discussed.

CONCLUSIONS

The availability of new options for diabetes therapy provides a chance for successful therapy in a larger number of patients. However, it is important to consider how much true benefit these new forms of treatment will have on the diabetic community. The best choice for a patient remains controversial.

Comparative tolerability of sulphonylureas in diabetes mellitus

The sulphonylurea drugs have been the mainstay of oral treatment for patients with diabetes mellitus since they were introduced. In general, they are well tolerated, with a low incidence of adverse effects, although there are some differences between the drugs in the incidence of hypoglycaemia. Over the years, the drugs causing the most problems with hypoglycaemia have been chlorpropamide and glibenclamide (glyburide), although this is a potential problem with all sulphonylureas because of their action on the pancreatic beta cell, stimulating insulin release. Other specific problems have been reported with chlorpropamide that occur only rarely, if at all, with other sulphonylureas. Hyponatraemia secondary to inappropriate antidiuretic hormone activity, and increased flushing following the ingestion of alcohol, have been well described. The progressive beta cell failure with time results in eventual loss of efficacy, as these agents depend on a functioning beta cell and are ineffective in the absence of insulin-producing capacity. Differences in this secondary failure rate have been reported, with chlorpropamide and gliclazide having lower failure rates than glibenclamide or glipizide. The reasons for this are unclear, but the more abnormal pattern of insulin release produced by glibenclamide may be partly responsible and, indeed, may explain the increased risk of hypoglycaemia with this agent. Previously reported increased mortality associated with tolbutamide therapy has not been substantiated, and more recent data have shown no increased mortality from sulphonylurea treatment. Indeed, benefit from glycaemic control, regardless of the agent used--insulin or sulphonylurea--was reported by the United Kingdom Prospective Diabetes Study. Nevertheless, there is still ongoing controversy in view of the experimental evidence, mainly from animal studies, of potential adverse effects on the heart from sulphonylureas, but these are difficult to extrapolate into clinical situations. Most of these studies have been carried out with glibenclamide, which makes comparison of possible risk difficult. Other cardiovascular risk factors may be modified by gliclazide, which seems unique among the sulphonylureas in this respect. Its reported haemobiological and free radical scavenging activity probably resides in the azabicyclo-octyl ring structure in the side chain. Reduced progression or improvement in retinopathy has been reported in comparative trials with other sulphonylureas, and the effect is unrelated to improvements in glycaemia. There are differences between the sulphonylureas in some adverse effects, risk of hypoglycaemia, failure rates and actions on vascular risk factors. As a group of drugs, they are very well tolerated, but differences in overall tolerability can be identified.

Novel oximes having 5-benzyl-2,4-thiazolidinedione as antihyperglycemic agents: synthesis and structure-activity relationship

Oximes having 5-benzyl-2,4-thiazolidinedione were prepared, and their PPAR gamma agonistic activities and blood glucose lowering activities were evaluated. Biaromatic and methyl groups, attached to the oxime moiety, and the ethylene bridge between oxime and phenoxy groups are favorable to biological activities.

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.

Pharmacological management of diabetes: recent progress and future perspective in daily drug treatment

Glycaemic control in Type 1 diabetes has been proven efficient in preventing microvascular and neurological complications. The assumption that good control of hyperglycaemia may also have significant impact on alleviation of complications in Type 2 diabetes has gained growing support in recent years. Measures such as body weight reduction and exercise improve the metabolic defects, but pharmacological therapy is most frequently used. The sulphonylureas stimulate insulin secretion. Metformin and troglitazone increase glucose disposal and decrease hepatic glucose output without causing hypoglycaemia. Acarbose helps to spread the dietary carbohydrate challenge to endogenous insulin over time. These pharmacological treatments can improve blood glucose regulation in Type 2 diabetes patients. However, the key to strict glycaemic control with use of exogenous insulin lies in the creation of delivery methods that emulate physiologic insulin secretion. Insulin lispro, a recombinant insulin analogue, is identical to human insulin except for the transposition of proline and lysine at positions 28 and 29 in the C-terminus of the B chain. Evidence suggests that patients perceive their quality of life to be improved with insulin lispro when compared with regular human insulin, and that satisfaction with treatment is greater with the insulin analogue. Numerous new pharmacological approaches are under active investigation, with the aim of promoting insulin secretion, improving the action of insulin, or slowing carbohydrate absorption. With respect to continuous subcutaneous insulin infusion therapy and implantable pumps, despite that this approach is not widely utilised, it appears to bring us as close to achieving glycaemic control as is feasible with current treatment approaches. However, general application of such technology requires significant improvements in several areas, such as improvement of patency of catheter, pump failures due to early battery depletion incidents, and pump miniaturisation. Future perspective resides on insulin analogues with longer half-lives that would provide better basal insulin coverage in association with fast-acting analogues.

Comparative effects of englitazone and glyburide on gluconeogenesis and glycolysis in the isolated perfused rat liver

Englitazone (CP 68,722, Pfizer) is a member of a family of drugs known as thiazolidinediones. One member of this family, troglitazone (Rezulin), is currently utilized in the treatment of Type 2 diabetes. Previous studies have focused on the ability of englitazone to increase insulin sensitivity in various tissues. However, little information is available regarding the direct effect of englitazone on hepatic glucose metabolism in the absence of insulin. Therefore, the following studies were conducted to comparatively evaluate the effect of englitazone and glyburide (a representative sulfonylurea) on gluconeogenesis and glycolysis from various substrates in the isolated perfused rat liver (IPRL). In isolated perfused rat livers of 24-hr fasted rats infused with lactate (2 mM), englitazone (6.25 to 50 microM) produced a concentration-dependent decrease (32-93%) in hepatic gluconeogenesis. When dihydroxyacetone (1 mM) and fructose (1 mM) were used as metabolic substrates, englitazone inhibited gluconeogenesis by 31 and 15%, respectively, while increasing glycolysis by 42 and 50%. Similar effects on gluconeogenesis and glycolysis were observed with glyburide, even though the effects with glyburide were more acutely evident, reversible, and of a greater magnitude. Such data suggest alterations in hepatic glucose production may contribute to the decrease in plasma glucose concentrations observed in individuals treated with englitazone and glyburide. These alterations may include effects on several regulatory enzymes (e.g. fructose-1,6-bisphosphatase, pyruvate kinase, and phosphoenolpyruvate carboxykinase), which warrant further investigation.

Oral antidiabetic agents. A guide to selection

Type 2 diabetes mellitus (formerly named non-insulin-dependent diabetes mellitus or NIDDM) is a heterogeneous disease resulting from a dynamic interaction between defects in insulin secretion and insulin action. Various pharmacological approaches can be used to improve glucose homeostasis via different modes of action: sulphonylureas essentially stimulate insulin secretion, biguanides (metformin) act by promoting glucose utilisation and reducing hepatic-glucose production, alpha-glucosidase inhibitors (acarbose) slow down carbohydrate absorption from the gut and thiazolidinediones (troglitazone) enhance cellular insulin action on glucose and lipid metabolism. These pharmacological treatments may be used individually for certain types of patients, or may be combined in a stepwise fashion to provide more ideal glycaemic control for most patients. Selection of oral antihyperglycaemic agents as first-line drug or combined therapy should be based on both the pharmacological properties of the compounds (efficacy and safety, profile) and the clinical characteristics of the patient (stage of disease, bodyweight, etc.). Mildly hyperglycaemic patients should preferably be treated with metformin, acarbose or thiazolidinediones (which are not associated with any hypoglycaemic risk), while more severely hyperglycaemic individuals should receive a sulphonylurea. In moderately hyperglycaemic patients, sulphonylureas should be preferred in nonobese patients while metformin, and probably also thiazolidinediones, should have priority in obese insulin-resistant type 2 diabetic patients. Acarbose is mainly indicated to reduce post-prandial glucose fluctuations and improve glycaemic stability. Each antihyperglycaemic agent may also be combined with insulin therapy to improve glycaemic control and/or reduce the insulin requirement of diabetic patients after secondary failure to oral treatment. Finally, safety should be taken into account in elderly patients and/or those with renal impairment, especially as far as the use of sulphonylureas (higher risk of hypoglycaemia) and metformin (higher risk of lactic acidosis) is concerned.

Intracellular targets for antidiabetic sulfonylureas and potassium channel openers

Antidiabetic sulfonylureas and potassium channel openers affect the activity of the ATP-regulated potassium channel (K(ATP) channel) present in the plasma membrane of various cells. This causes a broad spectrum of physiological responses, including the modulation of insulin release from pancreatic B-cells and the relaxation of smooth muscle. Recently, new targets for antidiabetic sulfonylureas and potassium channel openers were found in membranes of organelles, such as mitochondria and zymogen- and insulin-containing granules. By acting on these targets, the drugs modulate, independently of K(ATP) channel activity, insulin release from pancreatic B-cells, and they regulate K+ transport in mitochondria and zymogen granules. The interaction of sulfonylureas and potassium channel openers with intracellular targets gives additional basic information about their properties. Additionally, these studies could be important because of the medical applications of sulfonylureas and potassium channel openers.

Drug treatment of non-insulin-dependent diabetes mellitus in the 1990s. Achievements and future developments

Non-insulin-dependent diabetes mellitus (NIDDM, type 2 diabetes) is a heterogeneous disease resulting from a dynamic interaction between defects in insulin secretion and insulin action. There are various pharmacological approaches to improving glucose homeostasis, but those currently used in clinical practice either do not succeed in restoring normoglycaemia in most patients or fail after a variable period of time. For glycaemic regulation, 4 classes of drugs are currently available: sulphonylureas, biguanides (metformin), alpha-glucosidase inhibitors (acarbose) and insulin, each of which has a different mode and site of action. These standard pharmacological treatments may be used individually for certain types of patients, or may be combined in a stepwise fashion to provide more ideal glycaemic control for most patients. Adjunct treatments comprise a few pharmacological approaches which may help to improve glycaemic control by correcting some abnormalities frequently associated with NIDDM, such as obesity (serotoninergic anorectic agents) and hyperlipidaemia (benfluorex). There is intensive pharmaceutical research to find new drugs able to stimulate insulin secretion (new sulphonylurea or nonsulphonylurea derivatives, glucagon-like peptide-1), improve insulin action (thiazolidinediones, lipid interfering agents, glucagon antagonists, vanadium compounds) or reduce carbohydrate absorption (miglitol, amylin analogues, glucagon-like peptide-1). Further studies should demonstrate the superiority of these new compounds over the standard antidiabetic agents as well as their optimal mode of administration, alone or in combination with currently available drugs.

New concepts for treatment of non-insulin-dependent diabetes mellitus

Non-insulin-dependent diabetes mellitus remains a major cause of morbidity and premature mortality in our community. Although potentially amenable to control by lifestyle modification, this is difficult to achieve in practice. Additional approaches using drugs that enhance insulin secretion, suppress hepatic glucose production, and increase insulin sensitivity are available, and new agents are being developed. The thiazolidinedione drugs hold particular promise as insulin-sensitizing agents; however, at present, insulin administration is often also required. The importance of detection and treatment of risk factors for cardiovascular disease and the earlier detection and management of microvascular and infective complications remain of crucial importance. (Trends Endocrinol Metab 1997;8:187-191). (c) 1997, Elsevier Science Inc.

Oral antihyperglycaemics. Considerations in older patients with non-insulin-dependent diabetes mellitus

Non-insulin-dependent diabetes mellitus (NIDDM) is increasing in incidence as the population in most countries ages. Multiple pathology is common in the elderly, and cardiovascular disease is usually present at diagnosis. Patients who develop NIDDM at age 65 years may live long enough to develop microvascular complications. Others who are frail and have multiple pathologies may require treatment to prevent both symptomatic hyperglycaemia and dehydration, whilst avoiding hypoglycaemia. The goals in the management of NIDDM in elderly people are the prevention of complications and the relief of symptoms. Treatment must be tailored to the individual's expectations and should be reviewed regularly with the changing circumstances of aging. If dietary measures fail to control glucose levels, antihyperglycaemic sulphonylureas are the most frequently prescribed form of treatment. However, concern over the potential of these drugs to cause hypoglycaemia limits the choice to second generation sulphonylureas, agents that preserve the first phase of insulin release and have non-biologically active metabolites that are promptly eliminated. The biguanide agent metformin is also appropriate in elderly obese patients with NIDDM who do not have renal, liver or cardiac failure. The combination of a sulphonylurea and metformin can be effective in patients in whom insulin would otherwise be required. Novel compounds such as acarbose and the thiazolinediones may also be useful in the treatment of older diabetic patients.

Oral antidiabetic drug use in the elderly

Non-insulin-dependent diabetes mellitus (NIDDM) is a metabolic disease that is common in the elderly, and is characterised by insulin insufficiency and resistance. Measures such as bodyweight reduction and exercise improve the metabolic defects, but pharmacological therapy is the most frequently used and successful therapy. The sulphonylureas stimulate insulin secretion. Metformin and troglitazone increase glucose disposal and decrease hepatic glucose output without causing hypoglycaemia. Acarbose is a dietary aid that spreads the dietary carbohydrate challenge to endogenous insulin over time. These pharmacological agents, either alone or in combination, should improve blood glucose regulation in patients with NIDDM.

Drug therapy of non-insulin-dependent diabetes mellitus in the elderly

Non-insulin-dependent diabetes (NIDDM) is a common problem in the elderly. The discovery of several classes of oral antidiabetic agents has increased the prospects of achieving better control of hyperglycaemia with reduced risk of severe adverse events. Some of these agents, such as acarbose or miglitol, do not cause hypoglycaemia and act locally in the gut. As such they are safer agents. On the other hand, the low cost of some sulphonylurea agents and a once or twice daily administration schedule make them an attractive option. Metformin appears to be especially useful in obese insulin-resistant patients with NIDDM. However, obesity is not as much of a problem in the elderly as it is in middle-aged patients, and contraindications to the use of metformin are common in the elderly. The use of a combination of 2 or 3 oral antidiabetic agents to delay the need for insulin therapy is now possible. The long term effects of this approach are not known and the cost of polypharmacy is of concern.

Effects of aspirin and ibuprofen on the pharmacokinetics and pharmacodynamics of glyburide in healthy subjects

OBJECTIVE

To determine the effects of aspirin and ibuprofen on the pharmacokinetics and pharmacodynamics of glyburide in healthy volunteers.

DESIGN

Single-center, randomized, two-way, crossover design following an initial baseline evaluation phase.

SETTING

Outpatient, university-based ambulatory care facility.

PATIENTS

Sixteen healthy nonsmoking men aged 20-34 years.

INTERVENTION

Three phases consisting of six treatments. Phase 1 began with treatment A, a baseline oral glucose tolerance test (GTT), followed by treatment B, glyburide 5 mg plus a GTT. The other two phases were administered in a crossover design. Phase 2 consisted of the administration of aspirin 975 mg qid for 4 days. On day 3 a GTT was administered (treatment C) and on day 4 glyburide 5 mg plus a GTT was administered (treatment E). Phase 3 consisted of the administration of ibuprofen 600 mg qid for 4 days with a GTT on day 3 (treatment D) and glyburide 5 mg plus a GTT on day 4 (treatment F).

MAIN OUTCOME MEASURES

Serum glyburide concentrations after each treatment, as well as glucose and insulin, ibuprofen, and salicylate serum concentrations and glyburide free fractions.

RESULTS

Aspirin administration resulted in an 85% increase in mean total glyburide oral clearance and a 29% increase in glyburide free fraction. Ibuprofen administration resulted in a slight increase in mean glyburide free fraction, but no significant changes in glyburide pharmacokinetic parameters were observed. Insulin concentrations were increased during the glyburide plus aspirin treatment. Conflicting results were observed in the glucose parameters.

CONCLUSIONS

The potential for this glyburide-aspirin interaction resulting in a transient hypoglycemia should be considered in diabetic patients receiving glyburide therapy.

High-risk drugs in the elderly population

Drug therapy in elderly patients is affected by age-related changes in distribution and elimination and is further complicated by the increased sensitivity aged persons have to many of the effects of medications. Medications are often necessary in the elderly population, but care should be made to properly monitor these patients, especially those taking multiple drugs. Nurses, who are at the front lines of health care in all areas of practice, should be aware of drugs that may be high risk for use in the elderly and monitor these patients carefully for signs and symptoms of toxicity.

Cardiovascular effects of sulphonylurea derivatives. Implications for the treatment of NIDDM?

Sulphonylurea derivatives are widely used in the treatment of non-insulin-dependent diabetes mellitus. The mechanism of action of the insulino-tropic effect of these agents is based on the closure of adenosine-5'-triphosphate (ATP)-sensitive potassium channels (KATP-channels) in the beta cells of the pancreas. In the last decade, these KATP-channels have been demonstrated in myocardial cells as well as in vascular smooth muscle cells. During myocardial ischaemia, the KATP-channels are thought to open by a fall in the cytosolic ATP concentration. The increase in the extracellular adenosine concentration, and the release of endothelium-derived hyperpolarizing factor (EDHF) during ischaemia may further contribute to the opening of cardiovascular KATP-channels. Independently from the mechanism of opening, sulphonylurea derivatives have been reported to block the opening of cardiovascular KATP-channels. Related to the role of KATP-channel-opening in the (patho)physiology of ischaemia, the use of sulphonylurea derivatives significantly modifies the outcome of experimental myocardial infarction. Sulphonylurea derivatives impair the recovery of the contractile function and increase the ultimate infarct size in animal models. In contrast, sulphonylurea derivatives have a beneficial effect on the incidence of ventricular fibrillation as occurs after ischaemic incidents of the myocardium. Based on these experimental observations, human studies are indicated to investigate whether the use of these drugs modifies the clinical outcome of cardiovascular events in patients with non-insulin dependent diabetes mellitus.

Antihyperglycaemic agents. Drug interactions of clinical importance

Non-insulin-dependent (type 2) diabetes mellitus (NIDDM) affects middle-aged or elderly people who frequently have several other concomitant diseases, especially obesity, hypertension, dyslipidaemias, coronary insufficiency, heart failure and arthropathies. Thus, polymedication is the rule in this population, and the risk of drug interactions is important, particularly in elderly patients. The present review is restricted to the interactions of other drugs with antihyperglycaemic compounds, and will not consider the mirror image, i.e. the interactions of antihyperglycaemic agents with other drugs. Oral antihyperglycaemic agents include sulphonylureas, biguanides--essentially metformin since the withdrawn of phenformin and buformin--and alpha-glucosidase inhibitors, acarbose being the only representative on the market. These drugs can be used alone or in combination to obtain better metabolic control, sometimes with insulin. Drug interactions with antihyperglycaemic agents can be divided into pharmacokinetic and pharmacodynamic interactions. Most pharmacokinetic studies concern sulphonylureas, whose action may be enhanced by numerous other drugs, thus increasing the risk of hypoglycaemia. Such an effect may result essentially from protein binding displacement, inhibition of hepatic metabolism and reduction of renal clearance. Reduction of the hypoglycaemic activity of sulphonylureas due to pharmacokinetic interactions with other drugs appears to be much less frequent. Drug interactions leading to an increase in plasma metformin concentrations, mainly by reducing the renal excretion or the hepatic metabolism of the biguanide, should be avoided to limit the risk of hyperlactaemia. Owing to its mode of action, pharmacokinetic interferences with acarbose are limited to the gastrointestinal tract, but have not been extensively studied yet. Pharmacodynamic interactions are quite numerous and may result in a potentiation of the hypoglycaemic action or, conversely, in a deterioration of blood glucose control. Such interactions may be observed whatever the type of antidiabetic treatment. They result from the intrinsic properties of the coprescribed drug on insulin secretion and action, or on a key step of carbohydrate metabolism. Finally, a combination of 2 to 3 antihyperglycaemic agents is common for treating patients with NIDDM to benefit from the synergistic effect of compounds acting on different sites of carbohydrate metabolism. Possible pharmacokinetic interactions between alpha-glucosidase inhibitors and classical antidiabetic oral agents should be better studied in the diabetic population.

Antihyperglycaemic efficacy, response prediction and dose-response relations of treatment with metformin and sulphonylurea, alone and in primary combination

The short-term (2-12 weeks) antihyperglycaemic efficacy of metformin (M), glibenclamide (G), and their primary combination (MG) was assessed in a double-blind study including 165 unselected patients with Type 2 diabetes. Patients with diet failure were randomized to M, G or MG. The dose was titrated with a fasting blood glucose concentration (FBG) of < 6.7 mmol l-1 as the target, using at most six dose levels, the first three comprising increasing monotherapy (M or G) or low-dose primary combination (MGL), and the second three add-on therapies (M/G and G/M) and primary combination therapy escalated to high dose (MGH). Success rates were higher on MGL than on monotherapy. The difference in achieving acceptable control (FBG < or = 7.8 mmol 1(-1)) was 70% versus 51% (95% confidence interval 3-36%, p = 0.032). When the drugs were combined, a slightly greater FBG reduction (p = 0.026) was observed, at lower dosage (p = 0.013). The response could not be predicted from body weight, but depended upon initial FBG (p = 0.019) and meal-stimulated C-peptide (p = 0.007). FBG declined progressively with increasing doses of metformin, whereas glibenclamide exerted most of its effect at low dose. Primary combination therapy with metformin and sulphonylurea may be clinically useful.

Comparative tolerability profiles of oral antidiabetic agents

The sulphonylureas and the biguanides are widely used as adjuncts to dietary measures in the treatment of non-insulin-dependent (type 2) diabetes mellitus (NIDDM). Adverse effect profiles differ markedly between the sulphonylureas and biguanides, reflecting differences in chemical structure and mode of action. Sulphonylureas are generally well tolerated, although pharmacokinetic differences between these agents have important clinical implications. The main adverse effect associated with sulphonylureas is hypoglycaemia. This effect is a predictable consequence of the principal pharmacological effect of these drugs, i.e. sensitisation of the islet beta-cell to glucose, resulting in enhanced endogenous insulin secretion. Sulphonylurea-induced suppression of hepatic glucose production may cause profound and protracted hypoglycaemia, especially in elderly patients, in individuals with intercurrent illnesses and reduced caloric intake, or when taken in combination with other compounds with hypoglycaemic potential, e.g. alcohol (ethanol). Sulphonylureas with a longer duration of action, notably chlorpropamide and glibenclamide (glyburide), are more liable to induce serious hypoglycaemia, particularly when drug elimination is reduced by renal impairment. Other drugs such as salicylates may potentiate the actions of sulphonylureas, thereby increasing the risk of hypoglycaemia. Biguanide therapy is associated with alterations in lactate homeostasis which under certain clinical circumstances may result in fatal lactic acidosis. Phenformin is associated with a markedly greater risk of lactic acidosis than metformin. Phenformin has been withdrawn in many countries for this reason. All biguanides must be avoided in patients with renal impairment, hepatic dysfunction and cardiac failure--conditions where drug accumulation or disordered lactate metabolism may predispose to lactic acidosis. Phenformin should not be given to individuals who exhibit a severe, genetically conferred hepatic defect of hydroxylation which impedes metabolism of this drug. Less seriously, the biguanides are associated with a relatively high incidence of gastrointestinal adverse effects which limit compliance. Acarbose, a competitive inhibitor of intestinal alpha-glucosidases, has recently been introduced. In contrast to the sulphonylureas and biguanides, acarbose has not been associated with life-threatening adverse effects. This reflects the low systemic absorption of the drug and, predictably, its principal unwanted effects are gastrointestinal disturbances resulting from iatrogenic carbohydrate malabsorption.

alpha-Glucosidase inhibitors in diabetes: efficacy in NIDDM subjects

With alpha-glucosidase inhibitors generally improved metabolic control is achieved in NIDDM patients regardless of whether acarbose is administered in addition to other oral anti-diabetic agents or to diet alone. The most significant finding is the reduction of postprandial blood glucose concentrations. Long-term studies show a decrease in glycosylated haemoglobin and often also in fasting blood glucose levels. Placebo-controlled studies have proven that postprandial insulin concentrations are decreased under acarbose treatment while fasting plasma insulin is usually unchanged. The major side-effects of acarbose treatment involve the gastrointestinal system and include flatulence, abdominal discomfort and diarrhoea. Symptoms diminish with treatment time and are less severe when the treatment is started with low doses. Acarbose should usually be initiated as a 50 mg dose immediately before each major carbohydrate containing meal. Monotherapy with acarbose does not cause hypoglycaemia, however, hypoglycaemia may occur with combination of sulphonylurea or insulin treatment by the well-known reasons. In this case hypoglycaemia has to be treated by taking glucose.

Treatment of non-insulin-dependent diabetes mellitus and its complications. A state of the art review

Non-insulin-dependent diabetes mellitus (NIDDM) is a major health problem which occurs predominantly in the older population; 16.8% of persons over age 65 years have NIDDM. The total health costs of NIDDM are in excess of $US20 billion annually. The primary objective in the treatment of NIDDM is to achieve normoglycaemia, without aggravating coexisting abnormalities. Common abnormalities include obesity, hypertension, retinopathy, nephropathy and neuropathies. Diet, and consequent bodyweight reduction, is the cornerstone of therapy for NIDDM. Total calorie intake should be limited, while the percentage of calories from carbohydrates should be increased and that from fats and cholesterol should be decreased. Exercise may also help to reduce bodyweight. Sulphonylurea drugs stimulate insulin secretion from beta-cells, and may be a useful adjunct to nonpharmacological therapy. Failure to respond to sulphonylurea drugs may be primary (25 to 30% of initially treated patients) or secondary (5 to 10% per year). It is not clear which is the most effective pharmacological intervention in such cases. Options include switching to or combining therapy with insulin, a biguanide, or other insulin-sparing antihyperglycaemic agents, e.g. alpha-glucosidase inhibitors, thiazolidinediones, chloroquine or hydroxychloroquine, or fibric acid derivatives such as clofibrate. Other experimental agents include the fatty acid oxidation inhibitors and dichloroacetate. Specific agents, such as antihypertensives, lipid lowering agents and sorbitol inhibitors, may be needed to prevent the complications arising from the spectrum of clinical and metabolic abnormalities which arise from insulin resistance.

Potentiation of the hypoglycaemic response to glipizide in diabetic patients by histamine H2-receptor antagonists

In a randomised placebo controlled study, two groups of six maturity onset diabetic patients stabilised on glipizide were given cimetidine (400 mg) or ranitidine (150 mg) 3 h before a standardised meal. In comparison with placebo, both cimetidine and ranitidine significantly reduced the post-prandial rise in blood glucose by a mean of 40% and 25% respectively producing glucose levels of less than 3 mmol l-1 (lowest 1.5 mmol l-1) in four patients. Both drugs also significantly increased plasma glipizide AUC by approximately 20%. Caution should be exercised when initiating treatment with H2-receptor antagonists in diabetics receiving sulphonylurea hypoglycaemic agents.

Inappropriate use of high-dose glyburide to treat uncontrolled type 2 diabetes mellitus

OBJECTIVE

To report a case of chronic glyburide overdose.

CASE SUMMARY

A patient with noninsulin-dependent diabetes mellitus (NIDDM) who had previously developed secondary failure while taking a maximal dosage of glipizide was switched to glyburide 5 mg/d. The patient initially experienced adequate glycemic control while taking glyburide, but subsequently experienced deterioration in glycemic control. This necessitated gradual increases in the dosage of glyburide until the maximum dosage of 20 mg/d was reached. Because the patient's diabetic control did not improve with this dosage of glyburide, she decided independently to increase the dosage further. She ingested an average daily dose of 37.7 mg of glyburide over the 18 days that preceded her clinic visit without experiencing any glyburide-related adverse effects.

DISCUSSION

Progression of NIDDM may be responsible for the development of secondary sulfonylurea failure in NIDDM patients treated with oral sulfonylurea drugs. Consequently, these patients should be treated as patients dependent on insulin.

CONCLUSIONS

NIDDM patients treated with oral sulfonylurea drugs require long-term blood glucose monitoring to detect the development of secondary sulfonylurea failure. Patients who experience secondary failure to a particular sulfonylurea drug do not appear to develop long-term blood glucose control when switched to a different oral sulfonylurea drug. These patients should be treated with insulin therapy.

Comparison of the distribution of binding sites for the potassium channel ligands [125I]apamin, [125I]charybdotoxin and [125I]iodoglyburide in the rat brain

Potassium channels represent a diverse and promising target for drug development. Pharmacological subtypes of K channels have begun to emerge based on the development of both organic molecules and peptide toxins which possess subtype selectivity. In order to evaluate the neuroanatomical distribution of these subtypes we have utilized the ligands [125I]apamin, [125I]charybdotoxin and [125I]iodoglyburide in an autoradiographic study of rat brain. In the rat brain, these ligands have selectivity for the low conductance Ca(2+)-activated, voltage-gated K channels and ATP-sensitive K channels respectively. The distribution of binding sites for these three ligands were distinctly different. [125I]Apamin binding was highest in various thalamic and hippocampal structures, while only low to moderate levels of [125I]charybdotoxin binding were seen in these regions. In contrast, very high levels of [125I]charbydotoxin were seen in white matter regions such as the lateral olfactory tract and fasciculus retroflexus. High levels of [125I]charybdotoxin binding were also seen in gray matter-containing regions such as the zona incerta, medial geniculate and superior colliculus, where low to moderate [125I]apamin binding was found. [125I]Iodoglyburide presented a more uniform binding with the highest levels in the globus pallidus, islands of Calleja, anteroventral nucleus of the thalamus and zonas reticulata of the substantia nigra. These results indicate that subtypes of K channels have very different distributions in the brain. As such, the results imply differing CNS actions for potential modulators of K channel subtypes.

Pharmacotherapy of Oral Hypoglycemic Agents

The use of sulfonylurea in conjunction with a diet and exercise regimen continues to be the primary treatment modality for obese type II diabetics in the United States. These agents work to lower plasma glucose by several proposed mechanisms. Pancreatic mechanisms of action improve efficiency of the islet beta cells, and extrapancreatic mechanisms of action increase peripheral insulin-receptor sensitivity. Sulfonylureas are extensively metabolized in the liver. Depending on the specific agent, renally excreted metabolites with hypoglycemic activity may be produced and pose a threat to patients with impaired renal function. Accumulation of these metabolites can result in hypoglycemia, a common adverse reaction seen with the sulfonylurea. Other adverse reactions and their prevalence, presentation, and treatment are also presented. Clinically significant drug interactions of the sulfonylurea are tabulated and discussed. Because the sulfonlyureas have equivalent efficacy to each other, proper agent selection must be based on the metabolism and excretion characteristics, adverse reaction potential, and concurrent drug profile of the patient for whom the sulfonylurea is being selected. In patients who have not achieved adequate blood glucose control, combination therapy is sometimes initiated. Sulfonylurea-sulfonylurea and various sulfonylurea-insulin regimens are discussed. The importance of diabetic patient education is reviewed, including some basic instructions pharmacists can give to diabetics. The investigation of other oral hypoglycemic agents continues. Information of selected agents undergoing clinical trials in the United States is also reviewed.