Mealtime glucose regulation with nateglinide in healthy volunteers: comparison with repaglinide and placebo

Effect of co-ingestion of amino acids with rice on glycaemic and insulinaemic response

Consumption of high glycaemic index (GI) and glycaemic response (GR) food such as white rice has been implicated in the development of type 2 diabetes. Previous studies have reported the ability of individual amino acids to reduce GR of carbohydrate-rich foods. Because of the bitter flavour of amino acids, they have rarely been used to reduce GR. We now report the use of a palatable, preformed amino acid mixture in the form of essence of chicken. In all, sixteen healthy male Chinese were served 68 or 136 ml amino acid mixture together with rice, or 15 or 30 min before consumption of white rice. Postprandial blood glucose and plasma insulin concentrations were measured at fasting and every 15 min after consumption of the meal until 60 min after the consumption of the white rice. Subsequent blood samples were taken at 30-min intervals until 210 min. The co-ingestion of 68 ml of amino acid mixture with white rice produced the best results in reducing the peak blood glucose and GR of white rice without increasing the insulinaemic response. It is postulated that amino acid mixtures prime β-cell insulin secretion and peripheral tissue uptake of glucose. The use of ready-to-drink amino acid mixtures may be a useful strategy for lowering the high-GI rice diets consumed in Asia.

Pharmacologic treatment of type 2 diabetes: oral medications

OBJECTIVE

To review the oral and injectable pharmacologic treatment options for type 2 diabetes.

DATA SOURCES

A literature search was conducted using PubMed electronic database for studies published in English between 1993 and September 2014. Search terms included diabetes mellitus, type 2 diabetes, and the individual name for each antidiabetic medication reviewed. In addition, manual searches were performed for cross-references from publications. Package inserts, United States Food and Drug Administration (FDA) Web site, Institute for Safe Medication Practices Web site, American Diabetes Association Web site and scientific session poster presentations, and individual drug company Web pages were also reviewed.

STUDY SELECTION AND DATA EXTRACTION

This review focused on information elucidated over the past 10 years to assist prescribers in choosing optimal therapy based on individual patient characteristics. Studies leading to the approval of or raising safety concerns for the antidiabetic medications reviewed in this article were included.

DATA SYNTHESIS

In the past 10 years, there have been 4 novel oral antidiabetic medication classes and 9 new injectable agents and insulin products approved by the FDA for the treatment of type 2 diabetes as well as new information regarding the safety and use of several older antidiabetic medication classes. The distinctions were reviewed for each individual agent, and a comparison was completed if there was more than one agent in a particular therapeutic class. Using current information available, select investigational agents in phase III trials or those with a pending new drug application were highlighted.

CONCLUSION

There are now 9 distinct oral pharmacologic classes and a variety of insulin and noninsulin injectable medications available for the treatment of type 2 diabetes. Metformin remains the first-line treatment option for most patients. When considering options for alternative or additional treatment, prescribers must weigh the benefits and risks using individual patient characteristics.

Efficacy and safety of repaglinide vs nateglinide for treatment of Japanese patients with type 2 diabetes mellitus

Aims/Introduction:  Repaglinide is a short‐acting insulin secretagogue. We assessed the efficacy and safety of repaglinide in comparison with nateglinide in Japanese patients with type 2 diabetes previously treated with diet and exercise.

Materials and Methods:  In this 16‐week randomized, multicenter, double‐blind, parallel‐group, active‐controlled superiority trial, Japanese patients with type 2 diabetes and glycated hemoglobin (HbA_1c) of ≥6.9 and ≤9.4% were enrolled. Patients were randomly assigned to receive 0.5 mg repaglinide (n = 64) or 90 mg nateglinide (n = 66) three times a day. The primary end‐point was changes in HbA_1c from baseline to the end of treatment.

Results:  Mean reductions of HbA_1c were significantly greater for the repaglinide group than the nateglinide group (−1.17 ± 0.62 vs −0.81 ± 0.39%, P < 0.001). The target HbA_1c values of <6.9% were achieved by 75.0% of the repaglinide group vs 59.1% for nateglinide. Mean changes in fasting plasma glucose also showed significantly greater efficacy for repaglinide than nateglinide (−26.0 ± 20.9 vs −18.3 ± 17.8 mg/dL, P < 0.001). There were no differences in the adverse event rates between the repaglinide and the nateglinide group, by 57.8% (37/64) and 60.6% (40/66), respectively. Incidences of hypoglycemic symptoms were 17.2% (11/64, 28 events) in the repaglinide group and 6.1% (4/66, 20 events) in the nateglinide group, respectively.

Conclusions:  In type 2 diabetic patients treated with diet and exercise, repaglinide monotherapy gives greater glycemic improvement than nateglinide monotherapy in reducing HbA_1c and fasting plasma glucose values after 16 weeks. This trial was registered with JapicCTI (no. JapicCTI‐080521). (J Diabetes Invest, doi: 10.1111/j.2040‐1124.2011.00188.x, 2011)

The role of nateglinide and repaglinide, derivatives of meglitinide, in the treatment of type 2 diabetes mellitus

Type 2 diabetes mellitus (T2DM) is one of the most common chronic diseases worldwide, presenting a great challenge to the public health systems due to high morbidity and mortality, because of frequent micro-/macro-vascular complications. Many treatment options are now available, with different efficacy as well as mechanisms of action to improve deranged glucose metabolism. We review some of the available data on derivatives of meglitinide, namely nateglinide and repaglinide. These two compounds increase insulin secretion by a mechanism similar to the one of sulfonylureas, but with a shorter half-life. Nateglinide and repaglinide, derivatives of meglitinides, have characteristic pharmacodynamic and pharmacokinetic properties that, together with their proposed mechanism of action, make them useful for type 2 diabetes mellitus, especially when used in combination therapy.

Effect of CYP2C9 and SLCO1B1 polymorphisms on the pharmacokinetics and pharmacodynamics of nateglinide in healthy Chinese male volunteers

PURPOSE

Nateglinide is commonly used in the treatment of patients with type 2 diabetes mellitus. Our objective was to assess the association between CYP2C9 and SLCO1B1 polymorphisms and the metabolism of nateglinide in healthy Chinese male volunteers.

METHODS

A total of 35 healthy Chinese male volunteers with different CYP2C9 and SLCO1B1 genotypes were given a single oral dose of 120 mg nateglinide. Plasma concentrations of nateglinide and blood glucose level were measured up to 8 h.

RESULTS

In subjects with the CYP2C9*1/*3 & 521TT, CYP2C9*1/*1 & 521TC/CC and CYP2C9*1/*3 & 521TC genotype, AUC(0-∞) of nateglinide was 56 %, 34 % and 56 % higher (P = 0.002, P = 0.041 and P = 0.013, respectively), and the CL/F of nateglinide was 35 %, 11 % and 36 % lower (P = 0.000, P = 0.003 and P = 0.002, respectively) than that in the reference group. When only considering 521 T>C polymorphism, it had no significant association with the pharmacokinetics of nateglinide. CYP2C9*3 and 521 T>C polymorphisms were the significant predictors of the AUC(0-∞) and CL/F of nateglinide (adjusted multiple R(2) = 34 % and 43 %, respectively) according to multiple linear regression analyses, but they have no significant association with changes in the blood glucose-lowering effect of nateglinide.

CONCLUSIONS

Both SLCO1B1 521 T>C and the CYP2C9*3 polymorphisms can significantly affect the pharmacokinetics of nateglinide, but they could only partially explain the interindividual variability of plasma concentration of nateglinide. Moreover, 521 T>C and the CYP2C9*3 polymorphisms have no effect on pharmacodynamics of nateglinide in healthy Chinese male subjects.

Importance of postprandial glucose levels as a target for glycemic control in type 2 diabetes

Increasing evidence supports the importance of postprandial glucose (PPG) in glycemic control with regard to the development of complications in patients with diabetes. PPG plays a critical role in determining overall glycemic control, particularly in patients who are close to their glycemic goals. Data also indicate that postprandial hyperglycemia may have a greater effect on the development of cardiovascular complications compared with elevated fasting plasma glucose. Several antidiabetic agents that specifically target PPG are currently available, including glinides, glucagon-like peptide-1 mimetics, dipeptidyl peptidase-4 inhibitors, and rapid-acting insulin analogs. A more intensive approach to managing PPG may improve the care of patients with diabetes and, ultimately, the outcome of these patients.

Improvement of insulin sensitivity and beta-cell function by nateglinide and repaglinide in type 2 diabetic patients - a randomized controlled double-blind and double-dummy multicentre clinical trial

AIM

To evaluate the efficacy of nateglinide vs. repaglinide in blood glucose (BG) control and the effect on insulin resistance and beta-Cell function in patients with type 2 diabetes.

METHODS

A randomized controlled double-blind and double-dummy multicentre clinical trial was conducted. A total of 230 Chinese patients with type 2 diabetes were enrolled in five clinical centres. The patients were divided randomly into group A [repaglinide 1.0 mg three times daily (t.i.d.), n = 115] or group B (nateglinide 90 mg t.i.d., n = 115). At baseline and end of the 12-week clinical trial, standard mixed meal tolerance tests were performed.

RESULTS

A total of 223 patients (96.9%) completed the trial. There was no significant difference between repaglinide and nateglinide groups in the effects of reducing fasting blood glucose (FBG), 30-, 60- and 120-min BG during 12 weeks (p > 0.05). At week 12, no significant difference was shown between the two groups in BG or haemoglobin A(1c) (HbA(1c)) (p > 0.05). However, the effect on HbA(1c) in repaglinide group was stronger than that in nateglinide group (p < 0.05). After 12-week treatment, area under the curve (AUC) of BG decreased (p < 0.05), and AUC of insulin and C-peptide (CP) increased in both groups (p < 0.05). The effects of nateglinide on AUC of BG, insulin and CP were similar to that of repaglinide (p > 0.05). There was no significant difference between the two groups in AUC of BG, insulin or CP in week 12 (p > 0.05). Furthermore, homeostasis model assessment of insulin resistance (HOMA-IR) and beta-cell function indexes measured by HOMA-beta, DeltaI(30)/DeltaG(30) and (DeltaI(30)/DeltaG(30))/HOMA-IR were improved significantly in both groups during 12 weeks (p < 0.05). The effects of improving HOMA-IR and beta-cell function indexes in nateglinide group were comparable with that of repaglinide group (p > 0.05).

CONCLUSIONS

The efficacy of repaglinide and nateglinide in FBG, postprandial glucose excursion and early-phase insulin secretion is similar. But the effect of repaglinide 1.0 mg t.i.d. on HbA(1c) is stronger than that of nateglinide 90 mg t.i.d.. This trial had shown that nateglinide and repaglinide could comparably improve insulin sensitivity and beta-cell function.

Nateglinide improves postprandial hyperglycemia and insulin secretion in renal transplant recipients

BACKGROUND

Postprandial hyperglycemia (PPHG) frequently occurs among renal transplant recipients (RTR). Reduced early insulin response (EIR) after a meal leads to impaired suppression of endogenous glucose production and subsequently PPHG, which is a risk factor for cardiovascular disease. Nateglinide is a rapid acting insulin secretagogue inducing an EIR after a meal. Our main objective was to investigate the safety and effect of nateglinide treatment on postprandial plasma glucose excursions and insulin secretion in RTR with PPHG.

PATIENTS AND METHODS

A total of 14 Caucasian RTR with new-onset diabetes mellitus (NODM; n = 6) or impaired glucose tolerance (IGT; n = 8) were included. The insulin response and glucose excursions were measured for 240 min after a standardized liquid meal at baseline and after two-wk treatment with nateglinide.

RESULTS

Treatment with nateglinide was followed by a significant decrease in mean two-h plasma glucose from 10.5 mmol/L (3.1) to 7.6 mmol/L (2.1; p < 0.001) and a decline in total postprandial area under the curve (AUC) of glucose concentration (p < 0.001). Both estimated EIR and the late insulin response increased significantly (p = 0.008 and p = 0.003, respectively). No serious adverse event was observed during the study period.

CONCLUSIONS

Treating RTR with nateglinide for two-wk significantly improved PPHG, increased the insulin response following a standardized meal and was well tolerated.

Effect of genetic polymorphisms in cytochrome p450 (CYP) 2C9 and CYP2C8 on the pharmacokinetics of oral antidiabetic drugs: clinical relevance

Type 2 diabetes mellitus affects up to 8% of the adult population in Western countries. Treatment of this disease with oral antidiabetic drugs is characterised by considerable interindividual variability in pharmacokinetics, clinical efficacy and adverse effects. Genetic factors are known to contribute to individual differences in bioavailability, drug transport, metabolism and drug action. Only scarce data exist on the clinical implications of this genetic variability on adverse drug effects or clinical outcomes in patients taking oral antidiabetics. The polymorphic enzyme cytochrome P450 (CYP) 2C9 is the main enzyme catalysing the biotransformation of sulphonylureas. Total oral clearance of all studied sulphonylureas (tolbutamide, glibenclamide [glyburide], glimepiride, glipizide) was only about 20% in persons with the CYP2C9*3/*3 genotype compared with carriers of the wild-type genotype CYP2C9*1/*1, and clearance in the heterozygous carriers was between 50% and 80% of that of the wild-type genotypes. For reasons not completely known, the resulting differences in drug effects were much less pronounced. Nevertheless, CYP2C9 genotype-based dose adjustments may reduce the incidence of adverse effects. The magnitude of how doses might be adjusted can be derived from pharmacokinetic studies. The meglitinide-class drug nateglinide is metabolised by CYP2C9. According to the pharmacokinetic data, moderate dose adjustments based on CYP2C9 genotypes may help in reducing interindividual variability in the antihyperglycaemic effects of nateglinide. Repaglinide is metabolised by CYP2C8 and, according to clinical studies, CYP2C8*3 carriers had higher clearance than carriers of the wild-type genotypes; however, this was not consistent with in vitro data and therefore further studies are needed. CYP2C8*3 is closely linked with CYP2C9*2. CYP2C8 and CYP3A4 are the main enzymes catalysing biotransformation of the thiazolidinediones troglitazone and pioglitazone, whereas rosiglitazone is metabolised by CYP2C9 and CYP2C8. The biguanide metformin is not significantly metabolised but polymorphisms in the organic cation transporter (OCT) 1 and OCT2 may determine its pharmacokinetic variability. In conclusion, pharmacogenetic variability plays an important role in the pharmacokinetics of oral antidiabetic drugs; however, to date, the impact of this variability on clinical outcomes in patients is mostly unknown and prospective studies on the medical benefit of CYP genotyping are required.

Postprandial interstitial insulin concentrations in type 2 diabetes relatives

BACKGROUND

An endothelial barrier for the insulin transport from the circulation to the target tissues of insulin has previously been suggested to contribute to insulin resistance. The interstitial insulin concentration (I-insulin) and insulin kinetics following a mixed meal have, however, previously not been characterized in human adipose tissue.

SUBJECTS AND METHODS

Eight nondiabetic first-degree relatives (FDR) of type 2 diabetes patients were recruited. Their I-insulin was measured by microdialysis after a test meal with or without oral administration of the insulin secretagogue nateglinide (120 mg). In parallel, adipose tissue blood flow and lipolysis were measured by xenon-clearance and microdialysis, respectively.

RESULTS

The I-insulin increased after the test meal, and this response was more prominent on the day the subjects received the nateglinide tablet when compared with the day the subjects received the placebo tablet [I-insulin incremental area under the curve (IAUC) nateglinide 7612 +/- 3032 vs. Plac 4682 +/- 2613 pmol L(-1) min; P < 0.05, mean +/- SE]. However, the postprandial I-insulin(max)/P-insulin(max) ratio was similar on the two test days (nateglinide: 213 +/- 62 vs. 501 +/- 92 pmol L(-1), I/P-ratio: 0.38 +/- 0.06 and placebo: 159 +/- 39 vs. 410 +/- 74 pmol L(-1), I/P-ratio: 0.36 +/- 0.05). There was no difference in time of onset of insulin action in situ, or responsiveness, when comparing placebo and nateglinide.

CONCLUSIONS

Microdialysis can now be used to measure the I-insulin in human adipose tissue following a mixed meal. The data also showed that the transendothelial delivery of insulin occurs rapidly, supporting the concept that transcapillary insulin transfer is a nonsaturable process in nondiabetic first-degree relatives of type 2 diabetes patients.

Diabetes, prediabetes, and cardiovascular risk: shifting the paradigm

As the prevalence of diabetes continues to increase worldwide, diabetes-related macrovascular morbidity and mortality are becoming major health care problems. Epidemiologic evidence suggests this relationship begins early in the progression from normal glucose tolerance to frank diabetes. This report reviews this epidemiologic evidence linking early stages of glucose dysregulation with cardiovascular disease and discusses the results of major clinical trials demonstrating that lifestyle or pharmacologic intervention can reduce the incidence of diabetes in high-risk individuals. These observations indicate that early identification and aggressive treatment of subjects with impaired fasting glucose or impaired glucose tolerance have the potential to reduce both the incidence of diabetes and its related cardiovascular disease. Three clinical trials are being conducted to test whether early pharmacotherapy can reduce or delay the incidence of diabetes, and their results may well begin to shift the treatment paradigm toward earlier intervention.

Pharmacology of the meglitinide analogs: new treatment options for type 2 diabetes mellitus

The expression meglitinide analogs was introduced in 1995 to cover new molecules proposed as non-sulfonylurea insulinotropic agents and displaying structural analogy with meglitinide, such as repaglinide, nateglinide, and mitiglinide. Meglitinide analogs display, as judged by conformation analysis, a U-shaped configuration similar to that of antihyperglycemic sulfonylureas such as glibenclamide (glyburide) and glimepiride. In rat pancreatic islets incubated in the presence of 7.0 mmol/L D-glucose, repaglinide and mitiglinide demonstrate comparable concentration-response relationships for stimulation of insulin release, with a threshold value < 10 nmol/L and a maximal secretory response at about 10 nmol/L. Several findings indicate that meglitinide analogs provoke the closing of adenosine triphosphate-sensitive potassium channels, with subsequent gating of voltage-sensitive calcium channels. The effects of meglitinide analogs upon the binding of [3H]glibenclamide to islet cells membranes reinforces this concept. At variance, however, with other meglitinide analogs, the ionic and secretory response to repaglinide (10 micromol/L) is not rapidly reversible in perifused rat islets. In experiments conducted in vivo in control and diabetic rats, repaglinide provokes a greater and more rapid increase in plasma insulin concentration and an earlier fall in glycemia than glibenclamide or glimepiride. Onset of effect is also more rapid and duration of effect shorter with nateglinide versus glibenclamide. In clinical studies, single or repeated daily administration of repaglinide increased plasma insulin concentration in a dose-dependent manner, with an incremental peak reached about 2 hours after repaglinide intake. Plasma concentrations of repaglinide are about 5.0 microg/L 2-2.5 hours after oral intake of the drug. Despite the slow reversibility of repaglinide action in vitro, this drug offers advantages over glibenclamide in terms of the possible occurrence of hypoglycemia if a meal is missed. In volunteers receiving a single oral dose of nateglinide (120mg) 10 minutes before a standardized 800 Kcal breakfast, the plasma insulin concentration was higher 5, 10, and 20 minutes after meal intake than when they received a single dose of repaglinide (0.5 or 2.0mg) or placebo 10 minutes before breakfast. Peak plasma concentrations of nateglinide were reached within 2 hours in most volunteers. Peak plasma concentrations of mitiglinide were reached 30 minutes after a single oral dose in a representative volunteer. Mitiglinide significantly suppressed meal-induced elevations in blood glucose concentrations in a study of patients with type 2 diabetes. In conclusion, two obvious differences among these meglitinide analogs should be underlined. First, on a molar basis, nateglinide is somewhat less potent than repaglinide or mitiglinide, as an insulinotropic agent. The maximal secretory responses evoked by these three meglitinide analogs are, however, identical to one another. Secondly, and as already mentioned, the functional effects of nateglinide and mitiglinide are more rapidly reversible than those of repaglinide, for instance in perifused rat islets. The meglitinide analogs offer the advantage over the long-acting antihyperglycemic sulfonylurea glibenclamide of minimizing the risk of undesirable hypoglycemia.

Postprandial dysmetabolism and cardiovascular disease in type 2 diabetes

The worldwide prevalence of type 2 diabetes mellitus has reached epidemic proportions. The so-called traditional risk factors cannot fully explain the excessive cardiovascular disease risk of type 2 diabetic patients. Numerous studies indicate that postprandial metabolic derangements, most notably hyperglycaemia and hypertriglyceridaemia, which are exaggerated and prolonged in type 2 diabetes, are important cardiovascular disease risk factors since they induce oxidative stress and endothelial dysfunctions. This review discusses the current evidence showing that postprandial dysmetabolism may indeed constitute an important cardiovascular disease risk factor as well as the mechanisms underlying this association. Finally, some possible therapeutic options and recommendations for future research are discussed.

Beta-cell response during a meal test: a comparative study of incremental doses of repaglinide in type 2 diabetic patients

OBJECTIVE

To assess the effects of incremental doses of repaglinide on postprandial insulin and glucose profiles after a standard 500-kcal test meal.

RESEARCH DESIGN AND METHODS

Sixteen diet-treated Caucasians with type 2 diabetes (mean HbA(1c) 8.4%) were enrolled in this randomized, open-label, crossover trial. Subjects received 0.5, 1, 2, and 4 mg repaglinide or placebo in a random fashion, followed by a standard 500-kcal test meal on 5 separate study days, 1 week apart.

RESULTS

The insulinogenic index (DeltaI30/DeltaG30) and insulin area under the curve (AUC) from 0 to 30 min (AUC(0-30)) were higher with the 4-mg drug dose compared with the two lower doses and with 2 mg compared with 0.5 mg. On subgroup analysis, the incremental insulin responses were apparent only in the fasting plasma glucose (FPG) < 9-mmol/l subgroup of subjects and not in the FPG >9-mmol/l subgroup. There was a significant dose-related increase in the late postprandial insulin secretion (insulin AUC(120-240)), which resulted in hypoglycemia in four subjects. Proinsulin-to-insulin ratios at 30 and 60 min improved with increasing doses of repaglinide; higher drug doses (2 and 4 mg) were more effective than the 0.5- and 1-mg doses.

CONCLUSIONS

Significant dose-related increases in early insulin secretion were found only in less advanced diabetic subjects. In advanced diabetic patients, only the maximum dose (4 mg) was significant compared with placebo. Better proinsulin-to-insulin processing was noted with increasing drug doses.

Acute and long-term effects of nateglinide on insulin secretory pathways

Acute and chronic effects of the insulinotropic drug nateglinide upon insulin release were examined in the BRIN-BD11 cell line. Nateglinide (10-400 microm) stimulated a concentration-dependent increase (P<0.05-P<0.001) in insulin release at a non-stimulatory (1.1 mm) glucose concentration. The insulinotropic response to 200 microm nateglinide was increased at 30 mm (P<0.01), but not 5.6-16.7 mm glucose concentrations. In depolarized cells, nateglinide (50-200 microm) evoked K(ATP) channel-independent insulin secretion (P<0.05-P<0.001) in the absence and presence of 5.6-30.0 mm glucose (P<0.001). Exposure for 18 h to 100 microm nateglinide abolished the acute insulinotropic effects of 200 microm nateglinide, tolbutamide or glibenclamide, but had no effect upon the insulinotropic effect of 200 microm efaroxan. While 18 h exposure to 100 microm nateglinide did not affect basal insulin release or insulin release in the presence of 16.7 mm glucose, 25 microm forskolin or 10 nm PMA, significant inhibition of the insulinotropic effects of 20 mm leucine and 20 mm arginine were observed. These data show that nateglinide stimulates both K(ATP) channel-dependent and-independent insulin secretion. The maintained insulinotropic effects of this drug with increasing glucose concentrations support the antihyperglycaemic actions of nateglinide in Type II diabetes. Studies of the long-term effects of nateglinide indicate that nateglinide shares signalling pathways with sulphonylureas, but not the imidazoline efaroxan. This may be significant when considering a nateglinide treatment regimen, particularly in patients previously treated with sulphonylurea.

Postprandial hyperglycaemia in type 2 diabetes: pathophysiological aspects, teleological notions and flags for clinical practice

Type 2 diabetes subjects carry an excess risk for micro- and macrovascular disease and a higher cardiovascular morbidity and mortality rate. The beneficial impact of tight glycaemic control-evidenced by the integrated marker of fasting glucose and postprandial glucose values, the HbA1c-for the prevention of microvascular complications is definitely confirmed. Over the past few years, several studies have identified postprandial hyperglycaemia as a better predictor of cardiovascular or even of all-cause mortality, as well as an independent risk factor for atherosclerosis. The continuous glucose monitoring could offer a rationale means for the detection of postprandial hyperglycaemia and ultimately for its effective management. Advances in technology keep a promise for a reliable, convenient and closer to the idea of the artificial endocrine pancreas glucose sensor. Subcutaneous glucose levels charted by one of the new sensors were found to be well correlated with venous glucose measurements. Intervention for a healthy lifestyle is frequently hampered by patients' poor compliance. The availability of diverse antidiabetic agents provides options for targeting the glycaemic goal and a choice more fitted to the particularized pathophysiology of each individual subject. Drugs targeting postprandial glycaemia may prove to represent the 'sine qua non' for the 'return' of postprandial glucose values at a 'non-deleterious' threshold, either as monotherapy for the early stages of the disease or as combination therapy later in the progression of diabetes.

Sulfonylurea treatment of type 2 diabetes mellitus: focus on glimepiride

Sulfonylureas, which have evolved through two generations since their introduction nearly 50 years ago, remain the most frequently prescribed oral agents for treatment of patients with type 2 diabetes mellitus. Glyburide, glipizide, and glimepiride, the newest sulfonylureas, are as effective at lowering plasma glucose concentrations as first-generation agents but are more potent, better tolerated, and associated with a lower risk of adverse effects. Differences in their binding affinity to the beta-cell sulfonylurea receptor have been described, with preservation of cardioprotective responses to ischemia with glimepiride. Clinical studies have shown glimepiride to be safe and effective in reducing fasting and postprandial glucose levels, as well as glycosylated hemoglobin concentrations, with dosages of 1-8 mg/day. In comparative trials, glimepiride was as effective in lowering glucose levels as glyburide and glipizide, but glimepiride was associated with a reduced likelihood of hypoglycemia and a smaller increase in fasting insulin and C-peptide levels than glyburide, and a more rapid lowering of fasting plasma glucose levels than glipizide. Glimepiride also improves first-phase insulin secretion, which plays an important role in reducing postprandial hyperglycemia. Insulin secretagogues, specifically glimepiride, merit consideration as first-line therapy for patients with type 2 diabetes.

Clinical pharmacokinetics of nateglinide: a rapidly-absorbed, short-acting insulinotropic agent

The prevalence and medical and economic impact of type 2 diabetes mellitus is increasing in Western societies. New agents have been developed that act primarily to reduce postprandial glucose excursions, which may be of particular significance now that postprandial glucose excursions are known to be correlated with cardiovascular morbidity and mortality. Nateglinide is a phenylalanine derivative that blocks K+ channels in pancreatic beta-cells, facilitating insulin secretion. Nateglinide sensitises beta-cells to ambient glucose, reducing the glucose concentration needed to stimulate insulin secretion. The pharmacokinetics of nateglinide are characterised by rapid absorption and elimination, with good (73%) bioavailability. Nateglinide is more rapidly absorbed when given 0-30 minutes prior to meal ingestion than if given during the meal. Nateglinide is extensively metabolised, primarily by cytochrome P450 2C9, and eliminated primarily by the kidney. Nateglinide pharmacokinetics are linear over the dose range 60-240 mg. No significant pharmacokinetic alterations occur in renally impaired patients, in the elderly, or in mildly hepatically impaired patients. Nateglinide administered prior to meals stimulates rapid, short-lived insulin secretion in a dose-dependent manner, thus decreasing mealtime plasma glucose excursions. Its effects on insulin secretion are synergistic with those of a meal. With increasing nateglinide doses, the risk of hypoglycaemia also increases, but its incidence is low. Even if a meal is missed, and the patient skips the dose of nateglinide (as recommended in the event of a missed meal), the incidence of subsequent hypoglycaemia remains low compared with long-acting agents. The postprandial insulinotropic effects of nateglinide are more rapid than those of repaglinide and more rapid and greater than those of glibenclamide (glyburide), while producing less prolonged insulin exposure and less risk of delayed hypoglycaemia. Further investigation is required to determine if nateglinide inhibition of postprandial glucose excursions will help to prevent diabetic complications or preserve pancreatic beta-cell function.

A placebo-controlled crossover study comparing the effects of nateglinide and glibenclamide on postprandial hyperglycaemia and hyperinsulinaemia in patients with type 2 diabetes

AIM

This was a randomized, double blind, three period crossover study. The objective was to compare glucose, insulin and C-peptide 24 h profiles in patients with type 2 diabetes mellitus after dosing with nateglinide (given preprandially before three test meals), glibenclamide (administered once before breakfast) or placebo (given before three test meals).

METHODS

Fourteen patients underwent screening followed within 3 weeks by three treatment periods of 1 day, each separated by 7 days. Dosing followed a six-sequence balanced, two 3 x 3-replicated Latin square.

RESULTS

Mean peak serum insulin levels were lower after nateglinide (115 mU/l) than after glibenclamide (145 mU/l.h; p = 0.017) but higher than after placebo (79 mU/l; p = 0.001). However, peak insulin levels were reached earlier after nateglinide [mean time to peak (tmax) 1.7 h] compared to glibenclamide (mean tmax 2.1 h, p = 0.06). Total insulin exposure over the day was higher after glibenclamide compared with that following nateglinide (1216 vs. 1067 mU/l.h; p = 0.009). Similar findings were seen with serum C-peptide. Despite this, mean peak plasma glucose concentrations were lower following nateglinide (11.4 mmol/l from a baseline of 8.3 mmol/l) compared with glibenclamide (13.2 mmol/l from a baseline of 8.5 mmol/l; p = 0.001) and placebo (14.0 mmol/l from a baseline of 8.0 mmol/L; p < 0.001).

CONCLUSIONS

Nateglinide improves early prandial measures of insulin and glucose response to a standard meal, more so than glibenclamide, in people with type 2 diabetes.

Evaluation of a new insulinotropic agent by using an innovative technology: efficacy and safety of nateglinide determined by continuous glucose monitoring

Nateglinide, a new insulinotropic agent, specifically targets prandial glycemic excursions. Recently, innovative technologies have become available that provide the possibility to measure 72-h blood glucose values continuously. The aim of this study was to evaluate the effects of nateglinide on 24-h blood glucose profiles in diabetic patients. Eighteen patients with type 2 diabetes mellitus--seven on diet only and 11 on metformin monotherapy--participated in the study. Mean age was 60 years, mean diabetes' duration was 7.4 years, and mean hemoglobin A1c was 8.4%. They underwent a 72-h glucose monitoring using a continuous glucose monitoring system (CGMS, Medtronic MiniMed, Northridge, CA) under their usual diabetes therapy and a standardized breakfast. After this period, therapy with nateglinide, 120 mg three times a day before meals, was initiated. Three days later patients again underwent 72-h glucose monitoring. Mean blood glucose values and mean fasting blood glucose values decreased significantly, from 172 mg/dL before to 131 mg/dL (P< 0.0004) and from 172 mg/dL before to 126 mg/dL (P< 0.0005), respectively, with nateglinide therapy. Postprandial hyperglycemia, expressed as mean blood glucose over a time period of 2 h after a meal, declined significantly after all three daily meals. The number of blood glucose values above 140 mg/dL decreased from 207 without to 98 during nateglinide therapy. Nateglinide was not associated with hypoglycemia or other adverse events. We found in this study, using CGMS, that nateglinide has a glucose-lowering potency that not only affects postprandial hyperglycemia, but also overnight and fasting blood glucose values.

Influence of CYP2C9 and CYP2D6 Polymorphisms on the Pharmacokinetics of Nateglinide in Genotyped Healthy Volunteers

BACKGROUND

The oral hypoglycaemic drug nateglinide is eliminated from the human body via hepatic biotransformation and renal tubular secretion. According to in vitro data, about 70% of nateglinide intrinsic clearance may be mediated by cytochrome P450 (CYP) 2C9 and a smaller fraction by CYP3A4 and CYP2D6.

OBJECTIVE

To assess the impact of CYP2C9 polymorphisms and of the CYP2D6 poor metaboliser genotype on the pharmacokinetics of nateglinide and its effects on insulin, glucose and glucagon in plasma.

DESIGN AND PARTICIPANTS

A prospective clinical study in 26 healthy volunteers chosen for their CYP2C9 and CYP2D6 genotype was conducted with individuals carrying wild-type genotype as reference group.

METHODS

Serial plasma nateglinide, glucose, insulin and glucagon concentrations were measured over 34 hours after a 180 mg dose of nateglinide under challenge with 75 g of oral glucose at 0, 4 and 8 hours after nateglinide intake. Kinetics were evaluated by nonparametric methods and by population pharmacokinetic-pharmacodynamic modelling.

RESULTS

Significantly reduced oral nateglinide clearance was found in carriers of CYP2C9*3 alleles, (p < 0.01), whereas carriers of CYP2C9*2 alleles had kinetic parameters similar to those of carriers of the wild-type allele (p = nonsignificant). Median total clearances were 7.9, 8.4, 6.5, 6.9, 5.8 and 4.1 L/h in carriers of the CYP2C9 genotypes *1/*1, *1/*2, *2/*2, *1/*3, *2/*3 and *3/*3. Median clearance in three carriers of two deficient CYP2D6 alleles was 9.4 L/h. These differences in nateglinide kinetics due to CYP2C9 genotypes did not result in statistically significant differences in plasma glucose, insulin and glucagon. Pharmacokinetic-pharmacodynamic modelling revealed a minor effect of CYP2C9 genotype on insulin and glucose, and extrapolations indicated that carriers of the CYP2C9*3/*3 genotype may be at a slightly higher risk of hypoglycaemia compared with carriers of CYP2C9*1, particularly when taking nateglinide doses above 120 mg.

CONCLUSION

The effect of CYP2C9 polymorphisms on nateglinide kinetics may cause a slightly increased risk for hypoglycaemia, which may become relevant in diabetic patients.

Repaglinide : a pharmacoeconomic review of its use in type 2 diabetes mellitus

Repaglinide (Prandin), NovoNorm, GlucoNorm, an oral insulin secretagogue, was the first meglitinide analogue to become available for use in patients with type 2 diabetes mellitus. The drug lowers postprandial glucose excursions by targeting early-phase insulin release, an effect thought to be important in reducing long-term cardiovascular complications of diabetes. Repaglinide provided similar overall glycaemic control to that achieved with glibenclamide (glyburide), as assessed by glycosylated haemoglobin (HbA(1c)) and fasting blood glucose levels, and was generally well tolerated in well designed clinical trials. Its rapid onset and relatively short duration of action allow for flexible meal schedules. Two modelled US cost-effectiveness analyses projected lifetime costs and outcomes for a hypothetical cohort of patients with type 2 diabetes. Both analyses projected long-term complications using data on HbA(1c) level changes from short-term clinical trials. Repaglinide plus rosiglitazone was dominant over rosiglitazone in one analysis, and repaglinide plus metformin was dominant over nateglinide plus metformin in the other. A similar Canadian analysis showed a favourable incremental cost-effectiveness ratio (<dollars US 1000 per QALY gained; 2001 values) for patients who switched from a sulphonylurea to repaglinide versus those who remained on sulphonylurea therapy. Long-term outcomes were projected using short-term clinical trial data on postprandial blood glucose level changes in the Canadian study. All three cost-effectiveness analyses are available as abstracts/posters. Two US cost analyses (both published in full) have also been conducted comparing the short-term costs (<or=3 years) of repaglinide, with or without metformin, versus other oral antidiabetic regimens. Results of these analyses are somewhat equivocal because of study design issues and/or a lack of statistically significant differences between treatment groups. In conclusion, repaglinide as monotherapy or in combination with other antidiabetic agents, such as metformin or rosiglitazone, achieves good metabolic control, similar to that achieved with comparable glibenclamide regimens. Severe hypoglycaemic episodes are less common with repaglinide than some sulphonylureas, including glibenclamide. Modelled cost-effectiveness analyses conducted in North America showed favourable results for repaglinide-containing regimens versus comparators, largely attributed to projected reductions in long-term cardiovascular complications using short-term data on changes in glycaemic parameters from clinical trials. Results of these cost-effectiveness analyses (all of which have been published as abstracts/posters) should be interpreted with caution since various assumptions regarding long-term costs and outcomes were necessarily incorporated into the economic models. While repaglinide is a useful addition to the available treatment options in type 2 diabetes, potential long-term advantages versus other agents, such as reducing cardiovascular complications, require confirmation. The prevalence of diabetes mellitus is projected to increase to over 3% of the world's population ( approximate, equals 220 million people) by the year 2010. Globally, 97% of patients with diabetes have type 2 disease, although in industrialised countries the proportion of type 2 disease is about 90%. In 2010, an estimated 14.85 million individuals in the US and 2.88 million in the UK will be diagnosed with type 2 diabetes. In addition, approximately one-third to one-half of individuals with diabetes are unaware that they have the disease, and are therefore undiagnosed. Diabetes is associated with significant morbidity, mortality and economic consequences. For the year 2002 in the US, direct medical costs associated with diabetes (type 1 and 2) were estimated at dollars US 91.8 billion (70% of total costs) and indirect costs at dollars US 39.8 billion (30%), for a total of dollars US 132 billion. Data from more than 7000 patients in eight European countries indicate tha the mean cost per patient with diabetes was dollars US 2928 annually (1999 values), and the proportion of total healthcare expenditure directed toward diabetes ranged from 1.6% to 6.6% depending on the country. Several analyses focusing specifically on type 2 disease showed, not surprisingly, that costs were higher among patients with diabetic complications than in those without complications. Repaglinide, a meglitinide analogue, is an oral insulin secretagogue that reduces postprandial glucose excursions by targeting postprandial insulin release. In clinical trials in patients with type 2 diabetes, repaglinide was usually administered at a dosage of 0.5-4 mg three times daily before meals as monotherapy or in combination with other agents. In placebo-controlled trials of up to 24 weeks' duration in patients with type 2 diabetes, repaglinide achieved statistically significant improvements in glycaemic control, as assessed by glycosylated haemoglobin (HbA(1c)), fasting blood glucose (FBG) and/or postprandial blood glucose (PPBG) levels compared with placebo. Preprandial administration of repaglinide achieved similar glycaemic control to glibenclamide (glyburide) 1.75-15 mg/day and better glycaemic control than glipizide 5-15 mg/day in 1-year, double-blind, randomised trials in patients with type 2 disease, the vast majority of whom had previously received oral antidiabetic therapy. Several randomised, open-label studies have evaluated repaglinide as part of combination therapy over 3-6 months in patients with type 2 diabetes who had inadequate glycaemic control with previous drug therapy. In general, results showed statistically significant improvements in glycaemic control when repaglinide was used in combination with metformin, various thiazolidinediones, or metformin plus bedtime insulin compared with monotherapy with either comparator drug in each study (or metformin plus bedtime insulin in one trial). Other studies in this patient population indicate that metformin plus repaglinide is associated with significantly better glycaemic control than metformin plus nateglinide 60-120 mg three times daily over 16 weeks, and similar glycaemic control to that achieved with metformin in combination with either glibenclamide or glimepiride for up to 1 year. Good glycaemic control has also been achieved with preprandial administration of repaglinide in flexible meal schedules. This was demonstrated in a placebo-controlled trial and in a large, prospective survey of patients receiving repaglinide in a clinical setting. The tolerability profile of repaglinide is characterised by adverse events of mild-to-moderate intensity similar to those associated with sulphonylureas. The most frequently reported adverse events with repaglinide include hypoglycaemia, upper respiratory infection, headache, other respiratory events, musculoskeletal events and gastrointestinal events. Severe episodes of hypoglycaemia are rare with repaglinide and occur approximately 2-2.5 times less frequently than with sulphonylureas. In addition, available data indicate that repaglinide may be less likely to increase bodyweight than various commonly used sulphonylurea agents. In general, repaglinide is also well tolerated when used as part of combination therapy. Repaglinide is metabolised by the cytochrome P450 (CYP) 3A4 enzyme system and therefore has the potential to interact with other CYP3A4 substrates when administered concurrently. A number of studies in healthy volunteers have shown no clinically significant pharmacokinetic drug interactions when repaglinide was administered concomitantly with digoxin, theophylline, warfarin, cimetidine, ketoconazole, rifampicin (rifampin), ethinylestradiol, simvastatin or nifedipine. However, a clinically significant increase in systemic exposure to repaglinide occurs when clarithromycin and repaglinide are administered concurrently, which may necessitate a reduction in repaglinide dosage. Moreover, a potentially hazardous interaction occurs when gemfibrozil (alone or with itraconazole) is used concomitantly with repaglinide. In view of the marked increase in systemic exposure to repaglinide, the combination of repaglinide and gemfibrozil should be avoided if possible. Pharmacoeconomic Analyses of RepaglinideTwo US cost analyses have been conducted with repaglinide in patients with type 2 diabetes (both published in full). One was a retrospective analysis of pharmacy and medical claims data from a large managed care organisation in which costs were adjusted for age, gender and comorbidities. Total adjusted (year 2000) cost per patient over a 9-month period was numerically lower for those treated with a combination of repaglinide plus metformin (dollars US 8924) than for patients who received metformin only (dollars US 9448), metformin plus glibenclamide (dollars US 9576) or repaglinide only (dollars US 11910), although there were no statistically significant differences between treatment groups. The other study, a literature-based decision-tree analysis, projected the proportion of patients achieving a target HbA(1c) level (<7%) and the associated direct medical costs over a 3-year period from the time of diagnosis. Among six different treatment regimens evaluated, costs ranged from dollars US 6106 with glipizide gastrointestinal therapeutic system (GITS) to dollars US 9298 with repaglinide monotherapy (2001/2002 values). Probabilistic sensitivity analysis indicated that first-line therapy with glipizide GITS or metformin would be associated with lower total medical costs than rosiglitazone or repaglinide monotherapy. Three cost-effectiveness analyses, all of which are modelled studies published as abstracts and/or posters, have been conducted with repaglinide in patients with type 2 diabetes. (ABSTRACT TRUNCATED)

Pharmacokinetic interactions with rifampicin : clinical relevance

The antituberculosis drug rifampicin (rifampin) induces a number of drug-metabolising enzymes, having the greatest effects on the expression of cytochrome P450 (CYP) 3A4 in the liver and in the small intestine. In addition, rifampicin induces some drug transporter proteins, such as intestinal and hepatic P-glycoprotein. Full induction of drug-metabolising enzymes is reached in about 1 week after starting rifampicin treatment and the induction dissipates in roughly 2 weeks after discontinuing rifampicin. Rifampicin has its greatest effects on the pharmacokinetics of orally administered drugs that are metabolised by CYP3A4 and/or are transported by P-glycoprotein. Thus, for example, oral midazolam, triazolam, simvastatin, verapamil and most dihydropyridine calcium channel antagonists are ineffective during rifampicin treatment. The plasma concentrations of several anti-infectives, such as the antimycotics itraconazole and ketoconazole and the HIV protease inhibitors indinavir, nelfinavir and saquinavir, are also greatly reduced by rifampicin. The use of rifampicin with these HIV protease inhibitors is contraindicated to avoid treatment failures. Rifampicin can cause acute transplant rejection in patients treated with immunosuppressive drugs, such as cyclosporin. In addition, rifampicin reduces the plasma concentrations of methadone, leading to symptoms of opioid withdrawal in most patients. Rifampicin also induces CYP2C-mediated metabolism and thus reduces the plasma concentrations of, for example, the CYP2C9 substrate (S)-warfarin and the sulfonylurea antidiabetic drugs. In addition, rifampicin can reduce the plasma concentrations of drugs that are not metabolised (e.g. digoxin) by inducing drug transporters such as P-glycoprotein. Thus, the effects of rifampicin on drug metabolism and transport are broad and of established clinical significance. Potential drug interactions should be considered whenever beginning or discontinuing rifampicin treatment. It is particularly important to remember that the concentrations of many of the other drugs used by the patient will increase when rifampicin is discontinued as the induction starts to wear off.

Addition of nateglinide to rosiglitazone monotherapy suppresses mealtime hyperglycemia and improves overall glycemic control

OBJECTIVE

To determine the effects of nateglinide added to rosiglitazone monotherapy on glycemic control and on postprandial glucose and insulin levels in patients with type 2 diabetes.

RESEARCH DESIGN AND METHODS

This 24-week, multicenter, double-blind, randomized study compared the efficacy of nateglinide (120 mg a.c.) and placebo added to rosiglitazone monotherapy (8 mg q.d.) in 402 patients with type 2 diabetes with HbA(1c) between 7 and 11% (inclusive). Efficacy parameters tested included HbA(1c) and plasma glucose and insulin levels in the fasting state and after a standardized meal challenge. Safety data were also collected.

RESULTS

In placebo-treated patients, HbA(1c) did not change (Delta = 0.0 +/- 0.1%). In patients randomized to nateglinide, HbA(1c) decreased from 8.3 to 7.5% (Delta = -0.8 +/- 0.1%, P < 0.0001 vs. placebo). Target HbA(1c) (<7.0%) was achieved by 38% of patients treated with combination therapy and by 9% of patients remaining on rosiglitazone monotherapy. In nateglinide-treated patients, fasting plasma glucose levels decreased by 0.7 mmol/l, 2-h postprandial glucose levels decreased by 2.7 mmol/l, and 30-min insulin levels increased by 165 pmol/l compared with no changes from baseline of these parameters with placebo added to rosiglitazone (P < 0.001).

CONCLUSIONS

By selectively augmenting early insulin release and decreasing prandial glucose excursions, nateglinide produced a clinically meaningful improvement in overall glycemic exposure in patients with type 2 diabetes inadequately controlled with rosiglitazone. Therefore, nateglinide substantially improves the likelihood of achieving a therapeutic target of HbA(1c) <7.0%.

Pharmacological agents that directly modulate insulin secretion

Blood glucose levels are sensed and controlled by the release of hormones from the islets of Langerhans in the pancreas. The beta-cell, the insulin-secreting cell in the islet, can detect subtle increases in circulating glucose levels and a cascade of molecular events spanning the initial depolarization of the beta-cell membrane culminates in exocytosis and optimal insulin secretion. Here we review these processes in the context of pharmacological agents that have been shown to directly interact with any stage of insulin secretion. Drugs that modulate insulin secretion do so by opening the K(ATP) channels, by interacting with cell-surface receptors, by altering second-messenger responses, by disrupting the beta-cell cytoskeletal framework, by influencing the molecular reactions at the stages of transcription and translation of insulin, and/or by perturbing exocytosis of the insulin secretory vesicles. Drugs acting primarily at the K(ATP) channels are the sulfonylureas, the benzoic acid derivatives, the imidazolines, and the quinolines, which are channel openers, and finally diazoxide, which closes these channels. Methylxanthines also work at the cell membrane level by antagonizing the purinergic receptors and thus increase insulin secretion. Other drugs have effects at multiple levels, such as the calcineurin inhibitors and somatostatin. Some drugs used extensively in research, e.g., colchicine, which is used to study vesicular transport, have no effect at the pharmacological doses used in clinical practice. We also briefly discuss those drugs that have been shown to disrupt beta-cell function in a clinical setting but for which there is scant information on their mechanism of action.

Pharmacokinetics of nateglinide in renally impaired diabetic patients

Treatment of hyperglycemia in patients with diabetes mellitus and renal insufficiency is complicated by altered pharmacokinetics of hypoglycemic agents. This study evaluated the pharmacokinetic profile and safety of nateglinide, an amino acid derivative that improves early phase insulin secretion and reduces mealtime glucose excursions. This open-label, single-dose, two-center study included patients (mean age = 57 +/- 10 years) with type 1 or 2 diabetes with impaired renal function (IRF) (n = 10) or with renal failure undergoing hemodialysis (n = 10). Both groups were compared with age-, sex-, height-, and weight-matched healthy controls (n = 20). All participants received a single 120-mg dose of nateglinide immediately before breakfast. Pharmacokinetic and safety evaluations were undertaken up to 48 hours postdose. All 40 subjects completed the study. Plasma nateglinide concentrations increased rapidly in patients undergoing dialysis and matched healthy subjects (tmax = 0.95 vs. 0.78 h, respectively) and was comparable with patients with IRF and matched healthy subjects (tmax = 0.80 vs. 0.65 h, respectively). There were no statistically significant differences for Cmax or AUC0-t between the groups. Nateglinide was eliminated rapidly in all groups (t1/2 = 1.9-2.8 h). There was no correlation between the level of renal function and systemic exposure. There was a low extent of renal excretion of nateglinide in healthy subjects (11%) and diabetic patients with IRF (3%). Nateglinide was well tolerated. These data suggest that nateglinide is suitable for use in diabetic patients with IRF or with renal failure undergoing dialysis. Given the comparable absorption and elimination profiles of nateglinide in renally impaired and healthy subjects, no dose adjustment appears necessary in the renally impaired.

Pharmacotherapy of diabetes mellitus: implications for the prevention and treatment of cardiovascular disease

Diabetes mellitus in adults is associated with an increased risk of premature vascular disease and a higher mortality rate. The presence of other risk factors, often seen in diabetic patients, such as systemic hypertension, augments the rate of vascular diseases. Evidence is growing that tight control of hyperglycemia using insulin and/or oral hypoglycemic agents will modify this risk. More aggressive control of concomitant hypertension and/or hyperlipidemia is also required. Diabetic patients who have myocardial infarctions do worse than nondiabetic patients. Various strategies to improve outcomes include the use of tight blood glucose control, and various coronary interventions are currently under clinical study.

The effects of nateglinide following oral glucose load in impaired glucose tolerance subjects: rapid insulin stimulation by nateglinide in IGT subjects

This study was designed to determine the effect of a novel insulin secretagogue, nateglinide, on the glycemic response curve and early insulin secretion following oral glucose load in impaired glucose tolerance (IGT) subjects. Thirteen subjects were given a 75 g oral glucose tolerance test (75 g OGTT), the findings of which resulted in the diagnosis of IGT. The subjects returned to our hospital immediately. Eight subjects, in whom neither body weight nor life style (daily diet and exercise) was significantly altered during this period, were given 90 mg of nateglinide 5 min before a second oral glucose load in order to examine restoration of impaired early insulin secretion. Nateglinide administration resulted in the almost normalization of the glycemic response curve with restoration of impairment in early insulin response at 30 and 60 min after an oral glucose load. The area under the secreted insulin-time curve was not changed significantly by nateglinide administration. A single dose of nateglinide was shown to almost normalize the glycemic response curve after a 75 g OGTT and to restore impairment in early insulin response in IGT subjects.

No effect of the novel antidiabetic agent nateglinide on the pharmacokinetics and anticoagulant properties of warfarin in healthy volunteers

The novel hypoglycemic agent nateglinide is pharmacologically distinct from oral hypoglycemic agents such as sulfonylureas and repaglinide. The present study investigated the effects in healthy volunteers of multiple doses of nateglinide on the pharmacokinetics and pharmacodynamics of warfarin. The study comprised a randomized two-group, two-way crossover, open-label design in 12 healthy male subjects. One group of 6 subjects initially received a single oral dose of warfarin 30 mg and then, after a 7- to 14-day washout, received both warfarin and nateglinide (120 mgnateglinide, 10 min before meals for 4 days and a single dose of 30 mg warfarin on the second day). The alternate group of 6 subjects received treatments in the opposite order. Pharmacokinetic profiles were derived from plasma warfarin and nateglinide concentrations. Prothrombin measurements were evaluated in both periods as a measure of warfarin activity. When administered alone or in combination, there were no statistically significant differences in mean warfarin (R- and S-enantiomers) or nateglinide pharmacokinetic parameters. The concurrent administration of nateglinide and warfarin did not affect the maximal change in prothrombin time that follows warfarin administration. In this study, there was no evidence of an effect of coadministration of nateglinide on the pharmacodynamic action of warfarin or any pharmacokinetic interaction between warfarin and nateglinide.

Nateglinide improves early insulin secretion and controls postprandial glucose excursions in a prediabetic population

OBJECTIVE

The purpose of this study was to evaluate the metabolic effectiveness, safety, and tolerability of nateglinide in subjects with impaired glucose tolerance (IGT) and to identify a dose appropriate for use in a diabetes prevention study.

RESEARCH DESIGN AND METHODS

This multicenter, double-blind, randomized, parallel-group, fixed-dose study of 8 weeks' duration was performed in a total of 288 subjects with IGT using a 2:2:2:1 randomization. Subjects received nateglinide (30, 60, and 120 mg) or placebo before each main meal. Metabolic effectiveness was assessed during a standardized meal challenge performed before and after the 8-week treatment. All adverse events (AEs) were recorded, and confirmed hypoglycemia was defined as symptoms accompanied by a self-monitoring of blood glucose measurement < or =3.3 mmol/l (plasma glucose < or =3.7 mmol/l).

RESULTS

Nateglinide elicited a dose-related increase of insulin and a decrease of glucose during standardized meal challenges, with the predominant effect on early insulin release, leading to a substantial reduction in peak plasma glucose levels. Nateglinide was well tolerated, and symptoms of hypoglycemia were the only treatment-emergent AEs. Confirmed hypoglycemia occurred in 28 subjects receiving nateglinide (30 mg, 0 [0%]; 60 mg, 5 [6.6%]; 120 mg, 23 [26.7%]) and in 1 (2.3%) subject receiving placebo.

CONCLUSIONS

Nateglinide was safe and effective in reducing postprandial hyperglycemia in subjects with IGT. Preprandial doses of 30 or 60 mg nateglinide would be appropriate to use for longer-term studies to determine whether a rapid-onset, rapidly reversible, insulinotropic agent can delay or prevent the development of type 2 diabetes.

Type 2 diabetes management: a comprehensive clinical review of oral medications

Diabetes is a major and growing health problem in the US. An incredible array of different oral medications is now on the market. Clinicians should understand all these new medications and in which clinical picture they will work best.

Nateglinide improves glycaemic control when added to metformin monotherapy: results of a randomized trial with type 2 diabetes patients

AIMS/HYPOTHESIS

This study evaluated the addition of nateglinide, a d-phenylalanine derivative that restores early phase insulin release, to metformin in type 2 diabetes patients stabilized on high-dose metformin.

METHODS

This multicentre, double-blind, parallel group trial included 467 metformin-treated patients with glycosylated haemoglobin (HbA1c) between 6.8% and 11%. Patients were randomized to add nateglinide 60 mg, 120 mg or placebo before three meals to metformin 1000 mg b.i.d. for 24 weeks.

RESULTS

HbA1c was significantly reduced with nateglinide 60 mg and 120 mg plus metformin compared with metformin control (-0.36%, p = 0.003; -0.59%, p < 0.001 respectively). Greater benefits occurred if patients had elevated HbA1c at baseline (-1.38% with nateglinide 120 mg in patients with HbA1c > 9.5%). A modest fasting plasma glucose reduction was observed. Most symptoms suggestive of hypoglycaemia occurred in patients with low HbA1c levels (<or= 8%) at baseline, although no confirmed cases of hypoglycaemia occurred with nateglinide 60 mg in this patient group. Events suggestive of hypoglycaemia were confirmed in 1.1% of cases (plasma glucose <or= 3.3 mmol/l). Weight gain over 24 weeks was 0.9 kg with nateglinide 120 mg vs. metformin alone, and plasma lipids remained unchanged.

CONCLUSIONS/INTERPRETATION

In patients stabilized on high-dose metformin, the addition of nateglinide improved glycaemic control. The combination of these agents was well tolerated and both doses of nateglinide proved effective. The efficacy of nateglinide 60 mg and the low rate of hypoglycaemia observed at this dose make it suitable for patients close to their therapeutic target on metformin monotherapy.

Insulinotropic meglitinide analogues

The loss of early-phase insulin secretion is an important and early event in the natural history of type 2 diabetes. Because a normal pattern of insulin secretion is essential for the effective control of postprandial metabolism, a rational basis for the development of agents that target early-phase insulin release exists. Conventional oral hypoglycaemic agents do not target, or adequately control, postprandial glycaemia. The emergence of new classes of oral agent with a more specific mode of action provides, for the first time, an opportunity to restore early-phase insulin release. One such drug class is the meglitinide analogues (repaglinide, nateglinide, and mitiglinide). These drugs are ideally suited for combination use with metformin. They could also prove effective in combination with a thiazolidinedione, a drug class that targets insulin resistance. Exogenous insulin is frequently required in the late management of type 2 diabetes. However, one hope for newer combinations of diabetic drugs is that the functional life of the beta cell can be extended, thereby delaying the need for insulin injections.

Nateglinide therapy for type 2 diabetes mellitus

OBJECTIVE

To review the pharmacology, pharmacokinetics, dosing guidelines, adverse effects, drug interactions, and clinical efficacy of nateglinide.

DATA SOURCES

Primary and review articles regarding nateglinide were identified by MEDLINE search (from 1966 to January 2001); abstracts were identified through the Institute for Scientific Information Web of Science (from 1995 to January 2001) and the American Diabetes Association; additional information was obtained from the nateglinide product information.

STUDY SELECTION/DATA EXTRACTION

All articles and meeting abstracts identified from the data sources were evaluated and all information deemed relevant was included in this review. Much of the information was from abstracts or the product labeling, since few clinical studies have been published in the medical literature.

DATA SYNTHESIS

Nateglinide is a novel nonsulfonylurea oral antidiabetic agent that stimulates insulin secretion from the pancreas. It has a rapid onset and short duration of action, allowing administration before a meal to reduce postprandial hyperglycemia. Improvement in glycemic control with nateglinide monotherapy has been demonstrated in patients not previously treated with antidiabetic medications. Greater improvement in glycemic control was observed when nateglinide was administered in combination with metformin.

CONCLUSIONS

Nateglinide is similar to repaglinide, but has a quicker onset of action, quicker reversal, and does not usually require dosage titration. Based on the pharmacodynamics of nateglinide and repaglinide, nateglinide produces a more rapid postprandial increase in insulin secretion, and its duration of response is shorter than that of repaglinide. The risk of postabsorptive hypoglycemia should be lower than with either sulfonylureas or repaglinide.