Sitagliptin, an dipeptidyl peptidase-4 inhibitor, does not alter the pharmacokinetics of the sulphonylurea, glyburide, in healthy subjects

A web-based scoping review assessing the influence of smoking and smoking cessation on antidiabetic drug meabolism: implications for medication efficacy

Currently 1.3 billion individuals globally engage in smoking, leading to significant morbidity and mortality, particularly among diabetic patients. There is urgent need for a better understanding of how smoking influences antidiabetic treatment efficacy. The review underscores the role of cigarette smoke, particularly polycyclic aromatic hydrocarbons (PAHs), in modulating the metabolic pathways of antidiabetic drugs, primarily through the induction of cytochrome P450 (CYP450) enzymes and uridine diphosphate (UDP)-glucuronosyltransferases (UGTs), thus impacting drug pharmacokinetics and therapeutic outcomes. Furthermore, the review addresses the relatively uncharted territory of how smoking cessation influences diabetes treatment, noting that cessation can lead to significant changes in drug metabolism, necessitating dosage adjustments. Special attention is given to the interaction between smoking cessation aids and antidiabetic medications, a critical area for patient safety and effective diabetes management. This scoping review aims to provide healthcare professionals with the knowledge to better support diabetic patients who smoke or are attempting to quit, ensuring tailored and effective treatment strategies. It also identifies gaps in current research, advocating for more studies to fill these voids, thereby enhancing patient care and treatment outcomes for this at-risk population.

The simultaneous quantification of Sitagliptin and Irbesartan in rat plasma using the validated LC-MS/MS method is applied to a pharmacokinetic study

Irbesartan (IRB), an angiotensin II receptor AT1 blocker, is an antihypertensive agent commonly used with Sitagliptin (STG), a novel antidiabetic agent in diabetes. A finalised and validated LC-MS/MS method was used for the bioanalytical quantification of STG and IRB to be applicable to studies on the P.K drug-drug interactions between STG and IRB. Using a YMC triart C18 column (50 mm × 4.6 mm i.d., 3 µm), both the drugs and the Tolbutamide were separated using a gradient mode with a flow rate of 1 ml/min with run time of 5 min. For analyte detection, an LC-MS/MS system with multiple reaction monitoring (MRM) was used. The technique was validated across a concentration range of 5-1000 ng/ml, with the LLOQ for both analytes being 5 ng/ml. At all QC levels accuracies from spiked samples were > 83% for both drugs and internal standards. The accuracy for STG within-batch and between-batch was found within 98.4-107.2%, and for IRB was found within 92.4-102.5%. The precision for STG within batch and between batches was less than 12.3% CV, and for IRB was less than 10.2% CV at all concentration levels. The pharmacokinetic profiles of STG and IRB were successfully applied on simultaneous oral administration to rats. This method applies to pharmacokinetic multidrug interaction studies.

Bioequivalence of Ertugliflozin/Sitagliptin Fixed-Dose Combination Tablets and Coadministration of Respective Strengths of Individual Components

A fixed-dose combination (FDC) tablet of ertugliflozin, a selective inhibitor of sodium-glucose cotransporter 2, and sitagliptin, a dipeptidyl peptidase-4 inhibitor, was developed for the treatment of patients with type 2 diabetes mellitus. Four studies were conducted under fasted conditions to demonstrate bioequivalence of ertugliflozin/sitagliptin FDC tablets and individual components at respective strengths when coadministered in healthy subjects. All studies had open-label, randomized, 2-period, 2-sequence, single-dose crossover designs. In each study 18 or 19 subjects were enrolled and received an ertugliflozin/sitagliptin FDC tablet (5 mg/50 mg, 5 mg/100 mg, 15 mg/50 mg, or 15 mg/100 mg) and corresponding strengths of ertugliflozin and sitagliptin coadministered as individual components. For both ertugliflozin and sitagliptin, the 90%CIs for the ratio (FDC:coadministration) of geometric means for area under the plasma concentration-time profile from time 0 extrapolated to infinite time, and maximum observed plasma concentration, were within acceptance criteria for bioequivalence (80% to 125%). All adverse events were mild in intensity. The 4 studies demonstrated that each strength of FDC tablet is bioequivalent to the respective dose of coadministered individual components. This indicates that the known efficacy and tolerability of ertugliflozin and sitagliptin when coadministered can be translated to the use of a FDC formulation.

Antidiabetic treatment with gliptins: focus on cardiovascular effects and outcomes

The traditional oral pharmacological therapy for type 2 diabetes mellitus (T2DM) has been based on the prescription of metformin, a biguanide, as first line antihyperglycemic agent world over. It has been demonstrated that after 3 years of treatment, approximately 50 % of diabetic patients could achieve acceptable glucose levels with monotherapy; but by 9 years this had declined to only 25 %. Therefore, the implementation of a combined pharmacological therapy acting via different pathways becomes necessary, and its combination with a compound of the sulfonylurea group was along decades the most frequently employed prescription in routine clinical practice. Meglitinides, glitazones and alpha-glucosidase inhibitors were subsequently developed, but the five mentioned groups of oral antihyperglycemic agents are associated with variable degrees of undesirable or even severe cardiovascular events. The gliptins—also called dipeptidyl peptidase 4 (DPP4) inhibitors—are an additional group of antidiabetic compounds with increasing clinical use. We review the status of the gliptins with emphasis on their capabilities to positively or negatively affect the cardiovascular system, and their potential involvement in major adverse cardiovascular events (MACE). Alogliptin, anagliptin, linagliptin, saxagliptin, sitagliptin, teneligliptin and vildagliptin are the compounds currently in clinical use. Regardless differences in chemical structure and metabolic pathways, gliptins as a group exert favorable changes in experimental models. These changes, as an almost general rule, include improved endothelial function, reduction of inflammatory markers, oxidative stress ischemia/reperfusion injury and atherogenesis. In addition, increased adiponectin levels and modest decreases in lipidemia and blood pressure were reported. In clinical settings, several trials—notably the longer one, employing sitagliptin, with a mean follow-up period of 3 years—did not show an increased risk for ischemic events. Anyway, it should be emphasized that the encouraging results from basic science were not yet translated into clinical evidence, probably due the multiple and pleiotropic enzymatic effects of DPP4 inhibition. Moreover, when employing saxagliptin, while the drug was not associated with an augmented risk for ischemic events, it should be pinpointed that the rate of hospitalization for heart failure was significantly increased. Gliptins as a group constitute a widely accepted therapy for the management of T2DM, usually as a second-line medication. Nonetheless, for the time being, a definite relationship between gliptins treatment and improved cardiovascular outcomes remains uncertain and needs yet to be proven.

Pharmacotherapy of type 2 diabetes mellitus: an update on drug-drug interactions

The incidence of type 2 diabetes mellitus is increasing rapidly, as are the associated co-morbidities. Consequently, it has become necessary for a diabetic patient to take multiple medications at the same time to delay progression of the disease. This can put patients at an increased risk of moderate to severe drug interactions, which may threaten patients' life or may deteriorate the quality of their life. Hence, managing drug-drug interactions is the cornerstone of anti-diabetic therapy. Most of the clinically important drug-drug interactions of anti-diabetic agents are related to their metabolic pathways, but drugs that compete for renal excretion or impair renal status can also play an important role. In this review, we have examined the clinical implications and underlying mechanisms of drugs that are likely to alter the pharmacologic response of or cause adverse events with antidiabetic drugs, and we have outlined safe and efficacious treatment modalities.

Evaluation of pharmacokinetic drug interactions between gemigliptin (dipeptidylpeptidase-4 inhibitor) and glimepiride (sulfonylurea) in healthy volunteers

PURPOSE

Gemigliptin is approved for the treatment of type II diabetes mellitus. Sulfonylureas are commonly used in combination with other antidiabetic drugs to improve glycemic control. The objective of this study was to evaluate the pharmacokinetics, safety, and tolerability of gemigliptin and glimepiride combination therapy compared with those of monotherapies.

METHODS

A randomized, open-label, crossover study was performed on healthy Korean male volunteers. Each subject received the following treatments (A and B) with a 7-day washout period: treatment A consisted of gemigliptin 50 mg once daily administered orally for 6 days, followed by concomitant oral dosing of glimepiride 4 mg and gemigliptin 50 mg on day 7; treatment B consisted of a single dose of glimepiride 4 mg. Blood samples were collected up to 24-h postdose on day 6 (gemigliptin) and day 7 (gemigliptin and glimepiride) following treatment A, and on day 1 (glimepiride) following treatment B. Concentrations of gemigliptin, glimepiride, and metabolites were determined using validated liquid chromatography-tandem mass spectrometry (LC-MS/MS). Safety assessments were performed throughout the study.

RESULTS

Twenty-three subjects completed the study. The geometric mean ratios (GMRs) of C max,ss and AUC τ,ss for gemigliptin were 1.0097 [90 % confidence interval (CI) 0.924-1.103] and 0.9997 (90 % CI 0.976-1.024), respectively. For glimepiride, the GMRs of C max and AUClast were 1.031 (90 % CI 0.908-1.172) and 0.995 (90 % CI 0.902-1.097), respectively. Both combination and monotherapy were well tolerated, and no serious adverse events were reported.

CONCLUSION

Gemigliptin and glimepiride did not alter the pharmacokinetic properties of each other when they were co-administered in healthy volunteers, and were generally tolerated.

Sitagliptin: a review of its use in patients with type 2 diabetes mellitus

Sitagliptin (Januvia(®), Xelevia™, Glactiv(®), Tesavel(®)) is an orally administered, potent and highly selective inhibitor of dipeptidyl peptidase-4 (DPP-4) and was the first agent of its class to be approved for use in the management of adults with type 2 diabetes. Numerous randomized placebo- or active comparator-controlled trials have demonstrated the efficacy of sitagliptin in terms of improving glycaemic control in patients with type 2 diabetes, including its use as monotherapy, initial combination therapy (usually with fixed-dose combinations of sitagliptin/metformin), or add-on therapy to metformin or to other antihyperglycaemic drugs, with or without metformin. The primary endpoint of the clinical trials was the reduction from baseline in glycosylated haemoglobin (HbA1c), although sitagliptin also showed beneficial effects for other endpoints, such as the proportion of patients who achieved target HbA1c, and reductions from baseline in fasting plasma glucose (FPG) levels and 2-h postprandial glucose (PPG) levels. Sitagliptin was generally well tolerated in clinical trials, had a low risk of hypoglycaemia (although this depends on background therapy) and had a neutral effect on body weight. Despite concerns regarding a possible increased risk of rare pancreatic adverse events (e.g. pancreatitis) with glucagon-like peptide-1 (GLP-1)-based therapies, such as GLP-1 receptor agonists and DPP-4 inhibitors, no causal association has been found; regulators in Europe recently conducted a review of available data, concluding that there is little evidence that these drugs could cause pancreatic inflammation or pancreatic cancer. A similar review is planned in the USA and postmarketing surveillance will continue. Thus, oral sitagliptin is an effective and generally well tolerated treatment option for the management of patients with type 2 diabetes.

DPP-4 inhibitors: focus on safety

INTRODUCTION

Dipeptidyl peptidase inhibitors (DPP-4-i) are highly selective inhibitors of the enzyme DPP-4. They act by increasing levels of incretin hormones, which have potent effects on insulin and glucagon release, gastric emptying, and satiety. Our goal is to review the safety issues related to DPP-4-i.

AREAS COVERED

This review is based upon a PubMed search of the literature using keywords alogliptin, linagliptin, saxagliptin, sitagliptin and vildagliptin, DPP-4-i, glucagon-like polypeptide-1 agonists, as well as extensive personal clinical trial experience with each of these agents. The current DPP-4-i have very different chemical structures. Saxagliptin has significant cytochrome P450 metabolism and carries a risk of drug interactions. Linagliptin has primarily entero-hepatic excretion, a benefit in renally impaired patients. A concern arose related to congestive heart failure in the SAVOR TIMI trial of saxagliptin. Several major cardiac studies are underway, with two concluded. Despite lingering uncertainty related to pancreatitis and pancreatic cancer, large randomized trials have not shown an increased risk with DPP-4-i treatment. Cutaneous adverse effects occur with a low frequency with some of these agents.

EXPERT OPINION

DPP-4-i are an additional choice in the group of anti-hyperglycemics. Their principal advantage is a low incidence of hypoglycemia, making these agents desirable in patients such as the elderly and those with cardiac disease. Several large trials have hinted at less cardiac risk with DPP-4-i than with sulfonylureas. The CAROLINA Trial comparing linagliptin and glimepiride may provide a conclusive answer to this question.

Effect of canagliflozin on the pharmacokinetics of glyburide, metformin, and simvastatin in healthy participants

Drug-drug interactions between canagliflozin, a sodium glucose co-transporter 2 inhibitor, and glyburide, metformin, and simvastatin were evaluated in three phase-1 studies in healthy participants. In these open-label, fixed sequence studies, participants received: Study 1-glyburide 1.25 mg/day (Day 1), canagliflozin 200 mg/day (Days 4-8), canagliflozin with glyburide (Day 9); Study 2-metformin 2,000 mg/day (Day 1), canagliflozin 300 mg/day (Days 4-7), metformin with canagliflozin (Day 8); Study 3-simvastatin 40 mg/day (Day 1), canagliflozin 300 mg/day (Days 2-6), simvastatin with canagliflozin (Day 7). Pharmacokinetic parameters were assessed at prespecified intervals. Co-administration of canagliflozin and glyburide did not affect the overall exposure (maximum plasma concentration [Cmax ] and area under the plasma concentration-time curve [AUC]) of glyburide and its metabolites (4-trans-hydroxy-glyburide and 3-cis-hydroxy-glyburide). Canagliflozin did not affect the peak concentration of metformin; however, AUC increased by 20%. Though Cmax and AUC were slightly increased for simvastatin (9% and 12%) and simvastatin acid (26% and 18%) following coadministration with canagliflozin, compared with simvastatin administration alone; however, no effect on active 3-hydroxy-3-methyl-glutaryl-CoA (HMG-CoA) reductase inhibitory activity was observed. There were no serious adverse events or hypoglycemic episodes. No drug-drug interactions were observed between canagliflozin and glyburide, metformin, or simvastatin. All treatments were well-tolerated in healthy participants.

The pharmacokinetic considerations and adverse effects of DPP-4 inhibitors [corrected]

INTRODUCTION

Dipeptidyl-peptidase-4 (DPP-4) inhibitors are a class of anti-hyperglycemic agents with proven efficacy in patients with type 2 diabetes mellitus (T2DM).

AREAS COVERED

This review considers the pharmacokinetic profile, adverse effects and drug interactions of DPP-4 inhibitors. DPP-4 inhibitors have certain differences in their structure, metabolism, route of elimination and selectivity for DPP-4 over structurally related enzymes, such as DPP-8/DPP-9. They have a low potential for drug interactions, with the exception of saxagliptin that is largely metabolized by cytochrome CYP3A4/A5. Reports of pancreatitis and pancreatic cancer have raised concerns regarding the safety of DPP-4 inhibitors and are under investigation. Post-marketing surveillance has revealed less common adverse effects, especially a number of skin- and immune-related adverse effects. These issues are covered in the present review.

EXPERT OPINION

DPP-4 inhibitors are useful and efficient drugs. DPP-4 inhibitors have similar mechanism of action and similar efficacy. However, DPP-4 inhibitors have certain differences in their pharmacokinetic properties that may be associated with different clinical effects and adverse event profiles. Although clinical trials indicated a favorable safety profile, post-marketing reports revealed certain safety aspects that need further investigation. Certainly, more research is needed to clarify if the differences among DPP-4 inhibitors could lead to a different clinical and safety profile.

Comparative clinical pharmacokinetics of dipeptidyl peptidase-4 inhibitors

Dipeptidyl peptidase-4 (DPP-4) inhibitors collectively comprise a presently unique form of disease management for persons with type 2 diabetes mellitus. The aim of this review is to compare the clinical pharmacokinetics of available DPP-4 inhibitors (alogliptin, linagliptin, saxagliptin, sitagliptin and vildagliptin) for the purpose of identifying potential selection preferences according to individual patient variables and co-morbidities. DPP-4 inhibitors are readily absorbed orally. Following oral ingestion, absorption occurs mainly in the small intestine, with median times to maximum (peak) plasma concentration ranging from 1 to 3 hours. The fraction of each dose absorbed ranges from approximately 30% with linagliptin to 75-87% for all others. Numerical differences in maximum (peak) plasma drug concentrations and areas under the plasma concentration-time curve among the DPP-4 inhibitors vary by an order of magnitude. However, functional capacity measured in terms of glucose-lowering ability remains comparable among all available DPP-4 inhibitors. Distribution of DPP-4 inhibitors is strongly influenced by both lipophilicity and protein binding. Apparent volumes of distribution (V(d)) for most agents range from 70 to 300 L. Linagliptin exhibits a V(d) of more than 1000 L, indicating widespread distribution into tissues. Binding to target proteins in plasma and peripheral tissues exerts a major influence upon broadening linagliptin distribution. DPP-4 inhibitor metabolism is widely variable, with reported terminal half-lives ranging from approximately 3 to more than 200 hours. Complex relationships between rates of receptor binding and dissociation appear to strongly influence the durations of action of those DPP-4 inhibitors with comparatively shorter half-lives. Durations of activity often are not reflective of clearance and, with the exception of vildagliptin which may be administered either once daily in the evening or twice daily, these medications are effective when used with a once-daily dosing schedule. Saxagliptin and, to a lesser extent, sitagliptin are largely metabolized by hepatic cytochrome P450 (CYP) 3A4 and 3A5 isoforms. With the exception of the primary hydroxylated metabolite of saxagliptin, which is 2-fold less potent than its parent molecule, metabolic products of hepatic biotransformation are minimally active and none appreciably contribute to either the therapeutic or the toxic effects of DPP-4 inhibitors. No DPP-4 inhibitor has been shown to inhibit or to induce hepatic CYP-mediated drug metabolism. Accordingly, the number of clinically significant drug-drug interactions associated with these agents is minimal, with only saxagliptin necessitating dose adjustment if administered concurrently with medications that strongly inhibit CYP3A4. Linagliptin undergoes enterohepatic cycling with a large majority (85%) of the absorbed dose eliminated in faeces via biliary excretion. Other DPP-4 inhibitors predominantly undergo renal excretion, with 60-85% of each dose eliminated as unchanged parent compound in the urine. Systematic reviews of clinical trials suggest that the overall efficacy of DPP-4 inhibitors in patients with type 2 diabetes generally is similar. Apart from these generalizations, pharmacokinetic distinctions that potentially influence product selection are tentative. When considered in total, data reviewed in this report suggest that the best overall balance between potency and the clinical pharmacokinetic characteristics of distribution, metabolism and elimination may be observed with linagliptin followed closely by vildagliptin, saxagliptin, sitagliptin and alogliptin.

Clinical pharmacology of incretin therapies for type 2 diabetes mellitus: implications for treatment

BACKGROUND

Increased understanding of the role of incretin hormones in maintaining glucose homeostasis has enabled the development of pharmacotherapies that target deficient incretin activity in type 2 diabetes mellitus (T2DM). Incretin therapies are premised on 1 of 2 approaches: (1) augmenting the activity of the hormone glucagon-like peptide (GLP)-1 (GLP-1 receptor agonists) and (2) inhibiting the degradation of GLP-1 by dipeptidyl peptidase (DPP)-4 (DPP-4 inhibitors).

OBJECTIVE

This review discusses the pharmacokinetic properties and clinical profiles of the GLP-1 receptor agonists (exenatide twice daily, liraglutide once daily, exenatide once weekly, taspoglutide, and albiglutide) and the DPP-4 inhibitors (sitagliptin, saxagliptin, vildagliptin, and alogliptin) available for use or in late-stage development.

METHODS

A search of PubMed for literature published between 2000 and mid-2010 was conducted using the names of each agent as key words. Phase III and IV studies were included in the review of efficacy and tolerability. Supplemental searches of abstracts from major diabetes conferences provided additional information on pharmacokinetic properties. Searches of all reference lists were performed to identify additional references of interest.

RESULTS

The PubMed search identified multiple randomized, controlled clinical studies of the GLP-1 receptor agonists and the DPP-4 inhibitors administered as monotherapy or in combination regimens. Reductions from baseline in glycosylated hemoglobin ranged from 0.4% to 1.5% with exenatide 5 to 10 μg/d (7 studies), 0.6% to 1.5% with liraglutide 0.6 to 1.8 mg/d (6 studies), 0.3% to 1.0% with sitagliptin 25 to 200 mg/d (9 studies), 0.5% to 0.9% with saxagliptin 2.5 to 10 mg/d (3 studies), 0.4% to 1.0% with vildagliptin 50 to 100 mg/d (6 studies), and 0.4% to 0.8% with alogliptin 12.5 to 25 mg/d (4 studies). Dosage adjustments and caution in prescribing incretin therapies are recommended in patients with renal disease, with those recommendations varying based on the agent and the degree of dysfunction. Incretin therapies have been associated with few interactions with commonly used antihyperglycemic and cardiovascular therapies.

CONCLUSION

Based on the pharmacokinetic and therapeutic characteristics described in previously published Phase III and IV studies of incretin therapies, these agents may provide an option for the management of T2DM.

Advances in the treatment of type 2 diabetes mellitus

There is a rising worldwide prevalence of diabetes, especially type 2 diabetes mellitus (T2DM), which is one of the most challenging health problems in the 21st century. The associated complications of diabetes, such as cardiovascular disease, peripheral vascular disease, stroke, diabetic neuropathy, amputations, renal failure, and blindness result in increasing disability, reduced life expectancy, and enormous health costs. T2DM is a polygenic disease characterized by multiple defects in insulin action in tissues and defects in pancreatic insulin secretion, which eventually leads to loss of pancreatic insulin-secreting cells. The treatment goals for T2DM patients are effective control of blood glucose, blood pressure, and lipids (if elevated) and, ultimately, to avert the serious complications associated with sustained tissue exposure to excessively high glucose concentrations. Prevention and control of diabetes with diet, weight control, and physical activity has been difficult. Treatment of T2DM has centered on increasing insulin levels, either by direct insulin administration or oral agents that promote insulin secretion, improving sensitivity to insulin in tissues, or reducing the rate of carbohydrate absorption from the gastrointestinal tract. This review presents comprehensive and up-to-date information on the mechanism(s) of action, efficacy, pharmacokinetics, pleiotropic effects, drug interactions, and adverse effects of the newer antidiabetic drugs, including (1) peroxisome proliferator-activated-receptor-γ agonists (thiazolidinediones, pioglitazone, and rosiglitazone); (2) the incretin, glucagon-like peptide-) receptor agonists (incretin-mimetics, exenatide. and liraglutide), (3) inhibitors of dipeptidyl-peptidase-4 (incretin enhancers, sitagliptin, and vildagliptin), (4) short-acting, nonsulfonylurea secretagogue, meglitinides (repaglinide and nateglinide), (5) amylin anlog-pramlintide, (6) α-glucosidase inhibitors (miglitol and voglibose), and (7) colesevelam (a bile acid sequestrant). In addition, information is presented on drug candidates in clinical trials, experimental compounds, and some plants used in the traditional treatment of diabetes based on experimental evidence. In the opinion of this reviewer, therapy based on orally active incretins and incretin mimetics with long duration of action that will be efficacious, preserve the β-cell number/function, and block the progression of diabetes will be highly desirable. However, major changes in lifestyle factors such as diet and, especially, exercise will also be needed if the growing burden of diabetes is to be contained.

Retrospective analysis on the efficacy, safety and treatment failure group of sitagliptin for mean 10-month duration

BACKGROUND

To investigate the clinical results of sitagliptin (SITA) and the characteristics of the treatment failure group or of low responders to SITA.

METHODS

A retrospective study of type 2 diabetic patients reviewed 99 cases, including 12 treatment failure cases, who stopped SITA because of worsening patients' condition, and 87 cases, who continued treatment over five visits (total 9.9±10.1 months) after receiving the prescription of SITA from December 2008 to June 2009. Subjects were classified as five groups administered SITA as an initial combination with metformin (MET), add-on to metformin or sulfonylurea, and switching from sulfonylurea or thiazolidinedione. The changes in HbA1c level from the first to last visit (ΔHbA1c) in treatment maintenance group were subanalyzed.

RESULTS

The HbA1c level was significantly reduced in four groups, including initial coadministration of SITA with metformin (ΔHbA1c=-1.1%, P<0.001), add-on to MET (ΔHbA1c=-0.6%, P=0.017), add-on to sulfonylurea (ΔHbA1c=-0.5%, P<0.001), and switching from thiazolidinedione (ΔHbA1c=-0.3%, P=0.013). SITA was noninferior to sulfonlyurea (ΔHbA1c=-0.2%, P=0.63). There was no significant adverse effect. The treatment failure group had a longer diabeties duration (P=0.008), higher HbA1c (P=0.001) and fasting plasma glucose (P=0.003) compared to the maintenance group. Subanalysis on the tertiles of ΔHbA1c showed that low-response to SITA (tertile 1) was associated with a longer diabetes duration (P=0.009) and lower HbA1c (P<0.001).

CONCLUSION

SITA was effective and safe for use in Korean type 2 diabetic patients. However, its clinical responses and long-term benefit-harm profile is yet to be established.

Sitagliptin or exenatide once weekly for type 2 diabetes: comparison of the clinical trials

INTRODUCTION

There is a need for new and improved treatments for type 2 diabetes. Glucagon-like peptide 1 (GLP-1) is a gut hormone that stimulates insulin secretion and the levels of GLP-1 can be increased by inhibiting DPP-4. Sitagliptin is one of the DDP-4 inhibitors used to increase the levels of GLP-1. Exenatide is an agonist at the GLP-1 receptors, which is resistant to breakdown and has a longer action than GLP-1.

AREAS COVERED

This review compares the clinical trials of sitagliptin and exenatide once weekly in the treatment of type 2 diabetes. Only peer-reviewed trials listed on PubMed were included.

EXPERT OPINION

Both sitagliptin and exenatide once weekly are capable of reducing HbA1c and plasma glucose levels, but exenatide once weekly is more potent than sitagliptin and this may lead to different roles for these agents in the treatment of type 2 diabetes.

Dipeptidyl peptidase-4 inhibitors in the treatment of type 2 diabetes: a comparative review

The dipeptidyl peptidase (DPP)-4 inhibitors are a new class of antihyperglycaemic agents which were developed for the treatment of type 2 diabetes by rational drug design, based on an understanding of the underlying mechanism of action and knowledge of the structure of the target enzyme. Although they differ in terms of their chemistry, they are all small molecules which are orally available. There are some differences between them in terms of their absorption, distribution, metabolism and elimination, as well as in their potency and duration of action, but their efficacy, both in terms of inhibiting plasma DPP-4 activity and as antidiabetic agents, appears to be similar. They improve glycaemic control, reducing both fasting and postprandial glucose levels to lower HbA1c levels, without weight gain and with an apparently benign adverse event profile. At present, there seems to be little to distinguish between the different inhibitors in terms of their efficacy as antidiabetic agents and their safety. Long-term accumulated clinical experience will reveal whether compound-related characteristics lead to any clinically relevant differences.

Dipeptidylpeptidase-4 inhibitors (gliptins): focus on drug-drug interactions

Patients with type 2 diabetes mellitus (T2DM) are generally treated with many pharmacological compounds and are exposed to a high risk of drug-drug interactions. Indeed, blood glucose control usually requires a combination of various glucose-lowering agents, and the recommended global approach to reduce overall cardiovascular risk generally implies administration of several protective compounds, including HMG-CoA reductase inhibitors (statins), antihypertensive compounds and antiplatelet agents. New compounds have been developed to improve glucose-induced beta-cell secretion and glucose control, without inducing hypoglycaemia or weight gain, in patients with T2DM. Dipeptidylpeptidase-4 (DPP-4) inhibitors are novel oral glucose-lowering agents, which may be used as monotherapy or in combination with other antidiabetic compounds, metformin, thiazolidinediones or even sulfonylureas. Sitagliptin, vildagliptin and saxagliptin are already on the market, either as single agents or in fixed-dose combined formulations with metformin. Other compounds, such as alogliptin and linagliptin, are in a late phase of development. This review summarizes the available data on drug-drug interactions reported in the literature for these five DDP-4 inhibitors: sitagliptin, vildagliptin, saxagliptin, alogliptin and linagliptin. Possible pharmacokinetic interferences have been investigated between each of these compounds and various pharmacological agents, which were selected because there are other glucose-lowering agents (metformin, glibenclamide [glyburide], pioglitazone/rosiglitazone) that may be prescribed in combination with DPP-4 inhibitors, other drugs that are currently used in patients with T2DM (statins, antihypertensive agents), compounds that are known to interfere with the cytochrome P450 (CYP) system (ketoconazole, diltiazem, rifampicin [rifampin]) or with P-glycoprotein transport (ciclosporin), or agents with a narrow therapeutic safety window (warfarin, digoxin). Generally speaking, almost no drug-drug interactions or only minor drug-drug interactions have been reported between DPP-4 inhibitors and any of these drugs. The gliptins do not significantly modify the pharmacokinetic profile and exposure of the other tested drugs, and the other drugs do not significantly alter the pharmacokinetic profile of the gliptins or exposure to these. The only exception concerns saxagliptin, which is metabolized to an active metabolite by CYP3A4/5. Therefore, exposure to saxagliptin and its primary metabolite may be significantly modified when saxagliptin is coadministered with specific strong inhibitors (ketoconazole, diltiazem) or inducers (rifampicin) of CYP3A4/5 isoforms. The absence of significant drug-drug interactions could be explained by the favourable pharmacokinetic characteristics of DPP-4 inhibitors, which are not inducers or inhibitors of CYP isoforms and are not bound to plasma proteins to a great extent. Therefore, according to these pharmacokinetic findings, which were generally obtained in healthy young male subjects, no dosage adjustment is recommended when gliptins are combined with other pharmacological agents in patients with T2DM, with the exception of a reduction in the daily dosage of saxagliptin when this drug is used in association with a strong inhibitor of CYP3A4/A5. It is worth noting, however, that a reduction in the dose of sulfonylureas is usually recommended when a DPP-4 inhibitor is added, because of a pharmacodynamic interaction (rather than a pharmacokinetic interaction) between the sulfonylurea and the DPP-4 inhibitor, which may result in a higher risk of hypoglycaemia. Otherwise, any gliptin may be combined with metformin or a thiazolidinedione (pioglitazone, rosiglitazone), leading to a significant improvement in glycaemic control without an increased risk of hypoglycaemia or any other adverse event in patients with T2DM. Finally, the absence of drug-drug interactions in clinical trials in healthy subjects requires further evidence from large-scale studies, including typical subjects with T2DM - in particular, multimorbid and geriatric patients receiving polypharmacy.

Dipeptidyl peptidase-4 inhibitors for the treatment of type 2 diabetes mellitus

Type 2 diabetes mellitus traditionally has been characterized by insulin resistance and beta-cell dysfunction, leading to hyperglycemia and eventual micro- and macrovascular complications. Dipeptidyl peptidase-4 (DPP-4) inhibitors are a relatively new class of drugs available for the management of type 2 diabetes. In order to provide a comprehensive evaluation and comparison of the pharmacology, pharmacokinetics, efficacy, and safety of the DPP-4 inhibitors-sitagliptin, vildagliptin, saxagliptin, and alogliptin-in the treatment of type 2 diabetes, we conducted a MEDLINE search (1966-July 2009) for pertinent English-language articles. Abstracts of the annual meetings of the American Diabetes Association and European Association for the Study of Diabetes from 2005-2009 were also searched. As a drug class, the DPP-4 inhibitors have become widely accepted in clinical practice because of their low risk of hypoglycemia, favorable adverse-effect profile, and once-daily dosing. They are weight neutral (do not cause weight gain or loss) and appear to decrease beta-cell apoptosis and increase beta-cell survival. Because clinical studies directly comparing agents from this class have not, to our knowledge, been conducted, making comparisons in terms of efficacy and safety will become difficult for clinicians as more agents become available. Based on information from preclinical, clinical, and postmarketing data, there does not appear to be a compelling advantage of one DPP-4 inhibitor over another in terms of efficacy, safety, or ease of clinical use. Although theoretical advantages exist for agents with a higher specificity for DPP-4 inhibition versus inhibition of other isoenzymes associated with toxicity, comparative studies and/or increased clinical experience with this class of drug will determine the clinical advantages, if any, of one agent over another.

Sitagliptin: a review of its use in the management of type 2 diabetes mellitus

Sitagliptin (Januvia, Glactiv(R), Tesavel(R)) is a dipeptidyl peptidase-4 inhibitor indicated for the treatment of type 2 diabetes mellitus. Oral sitagliptin as monotherapy or combination therapy was generally well tolerated and improved glycaemic control in well designed clinical trials in patients with type 2 diabetes. Glycosylated haemoglobin (HbA(1c)) levels were significantly reduced with sitagliptin monotherapy relative to voglibose monotherapy or placebo, and with sitagliptin as initial combination therapy with metformin or pioglitazone relative to monotherapy with these agents or placebo. Moreover, sitagliptin monotherapy was noninferior to metformin monotherapy in terms of the reduction in HbA(1c) levels. Significant reductions in HbA(1c) levels, relative to background therapy, were also observed with sitagliptin add-on therapy to ongoing treatment with thiazolidinediones, sulfonylureas or insulin with or without metformin, or metformin alone. In terms of the reduction in HbA(1c) levels as add-on treatment to metformin, sitagliptin was noninferior to glipizide and generally did not differ from rosiglitazone, and as add-on treatment to pioglitazone, it did not differ significantly from metformin. Sitagliptin had a low risk of hypoglycaemia (except when used in combination with agents that may be associated with hypoglycaemia, such as sulfonylureas or insulin) and was generally weight-neutral. Although additional comparative data and longer-term studies with glycaemic and clinical outcomes are required to definitively position sitagliptin relative to other antihyperglycaemic agents, current evidence suggests that it is a useful treatment option for patients with type 2 diabetes, with potential advantages including oral administration, a generally weight-neutral effect and a low risk of hypoglycaemia.

Dipeptidyl peptidase-4 inhibitors in the management of type 2 diabetes: safety, tolerability, and efficacy

Although glycemic control is an important and effective way to prevent and minimize the worsening of diabetes-related complications, type 2 diabetes is a progressive disease which often proves difficult to manage. Most affected patients will eventually require therapy with multiple medications in order to reach appropriate glycemic targets. The dipeptidyl peptidase-4 (DPP-4) inhibitors constitute a relatively new class of oral medications for the treatment of type 2 diabetes, which has become widely incorporated into clinical practice. This review summarizes the available data on the efficacy, safety, and tolerability of these medications.

DPP-4 inhibitors in clinical practice

Type 2 diabetes is a very common worldwide disorder, with major consequences for patients, society, and health care services. Good glycemic control is an important aspect of diabetes management because it has a significant impact on diabetes-related microvascular and possibly macrovascular complications. Based on our understanding of the pathogenesis of diabetes, multiple pharmacological interventions have been developed in the past 60 years. Although effective, none have had a lasting effect on glycemic control because of the progressive nature of type 2 diabetes requiring combination therapies and insulin treatment. In addition, several pharmacologic interventions have undesirable side effects, including hypoglycemia and weight gain. Drugs targeting the incretin pathway are the latest addition to the available antidiabetes agents. Incretin-based therapy is either delivered orally (dipeptidyl peptidase-4 [DPP-4]) inhibitors or injected subcutaneously (glucagon-like peptide-1 [GLP-1] mimetics and analogues). Dipeptidyl peptidase-4 inhibitors are effective either as a single or combination therapy in lowering glycated hemoglobin, fasting and postprandial glucose levels, with a low incidence of hypoglycemia and no weight gain. There are 3 DPP-4 inhibitors currently available (sitagliptin, saxagliptin, and vildagliptin), with more expected to be available in the future. In this article, we review the scientific background for incretin-based therapy and the available evidence regarding the role and efficacy of DPP-4 inhibitors in the treatment of patients with type 2 diabetes.

Multiple doses of sitagliptin, a selective DPP-4 inhibitor, do not meaningfully alter pharmacokinetics and pharmacodynamics of warfarin

Sitagliptin is an orally active, highly selective dipeptidyl peptidase IV (DPP-4) inhibitor for treatment of type 2 diabetes mellitus. This randomized, open-label, 2-part, 2-period crossover study assessed pharmacokinetics/pharmacodynamics of warfarin in the presence/absence of multiple-dose sitagliptin. Twelve participants received treatments A and B separated by >7-day washout: treatment A involved coadministration of sitagliptin 200 mg/d for 11 days (days 1-11) and warfarin 30 mg on day 5, and treatment B involved warfarin 30 mg alone on day 1. R(+) warfarin, S(-) warfarin, and international normalized ratio (INR) were assayed predose and up to 168 hours postdose. The geometric mean ratios (GMRs; warfarin + sitagliptin/warfarin alone) (90% confidence intervals [CIs]) were 0.99 (0.95, 1.03) and 0.95 (0.90, 1.02) for the AUC(0-infinity) of R(+) and S(-) warfarin, respectively. GMRs (warfarin + sitagliptin/warfarin alone) (90% CIs) were 0.89 (0.86, 0.93) and 0.89 (0.86, 0.92) for the C(max) of R(+) and S(-) warfarin, respectively. INR AUC(0-168 h) and INR(max) GMRs were 1.01 (0.96, 1.06) and 1.08 (1.00, 1.17), respectively. Coadministration of sitagliptin and warfarin was generally well tolerated. Pharmacokinetics (AUC for R(+) and S(-) warfarin) and pharmacodynamics (INR of R(+) or S(-) warfarin) were not meaningfully altered following coadministration of multiple-dose sitagliptin and single-dose warfarin, indicating that no dosage adjustment for warfarin is necessary when coadministered with sitagliptin.

Incretin-based therapies: review of the outpatient literature with implications for use in the hospital and after discharge

A large percentage of critically ill adult inpatients have type 2 diabetes, which may be undiagnosed or uncontrolled during hospitalization. Hyperglycemia complicates the therapeutic management of inpatients and leads to adverse outcomes, and intensive glycemic control with insulin reduces morbidity and mortality. Insulin therapy, however, is labor-intensive and time-consuming. More important, long-standing protocols such as the sliding scale do not provide adequate glucose control. Although more research is needed to determine the best methods for treating hyperglycemia in-hospital, the importance of achieving better glycemic control while reducing the risk of hypoglycemia has been demonstrated. Post-discharge diabetes care is equally important, as it is essential in improving long-term outcomes after a hospital stay. Hospital care providers can play an important role in effective antihyperglycemic regimens in patients with diabetes prior to discharge. Post-discharge management is a formidable challenge because of the availability of an array of oral antidiabetes agents, including metformin, sulfonylureas, and thiazolidinediones, each with distinct therapeutic and adverse event profiles. Incretin-based therapies offer a potentially useful option for post-discharge therapy, and possibly for inpatient diabetes treatment. Incretins are effective, safe, and well-tolerated; they are easier for patients to use compared with insulin injections (eg, continual glucose monitoring is not required); and they may provide long-term improvement of cardiovascular parameters and beta-cell function. This review examines the challenges to achieving glycemic control in the hospital setting and summarizes clinical data on the efficacy and safety of incretin-based therapies in their use in the hospital and after discharge.

Glycaemic control in type 2 diabetes: targets and new therapies

Type 2 diabetes mellitus (T2DM) is a worldwide public health challenge. Despite the availability of many antidiabetes agents and pharmacotherapies targeting cardiovascular risk factors, the morbidity, mortality and economic consequences of T2DM are still a great burden to patients, society, health care systems and the economy. The need for new therapies for glycaemic control is compounded by the fact that existing treatments have limitations either because of their side effects (particularly weight gain and hypoglycaemia) or contraindications that limit their use. Furthermore, none of the current therapies have a significant impact on disease progression. Incretin-based therapies offer a new therapeutic approach to the management of T2DM, and there are also several even newer therapies in development. There are two groups of incretin-based therapies currently available; dipeptidyl peptidase-4 (DPP-4) inhibitors and GLP-1 analogues/mimetics. The former are given orally while the latter subcutaneously. These drugs result in glucose-dependent insulin secretion and glucose-dependent glucagon suppression, with consequent low risk of hypoglycaemia when used as mono- or combination therapy (except when used with sulphonylureas). In addition, they are either weight neutral in the case of DPP-4 inhibitors or cause weight loss in the case of incretin mimetics/analogues. Furthermore, animal studies have shown that these agents prolong beta cell survival which offers the theoretical possibility of slowing the progression to T2DM. In this article we will review the currently available antidiabetes agents with particular emphasis on incretin-based and future therapies. In addition, we will review and discuss the evidence relating to glycaemic control and cardiovascular disease.

Differential chemistry (structure), mechanism of action, and pharmacology of GLP-1 receptor agonists and DPP-4 inhibitors

OBJECTIVE

To review the pharmacology (absorption, metabolism, distribution, elimination, and contraindications) of incretin-based agents currently available and in regulatory review for the treatment of patients with type 2 diabetes.

DATA SOURCES

Medline search of all relevant clinical and review articles.

STUDY SELECTION

English-language articles pertinent to the pharmacology, pharmacodynamics, pharmacokinetics, efficacy, and safety of glucagon-like peptide-1 (GLP-1) agonists and dipeptidyl peptidase-4 (DPP-4) inhibitors were reviewed for relevance.

DATA EXTRACTION

Data pertinent to the pharmacology, pharmacodynamics, pharmacokinetics, efficacy, and safety of GLP-1 agonists and DPP-4 inhibitors were extracted and used.

DATA SYNTHESIS

Incretin hormones are secreted from the gastrointestinal tract following meal ingestion, the two most important of which are glucose-dependent insulinotropic polypeptide (GIP) and GLP-1. Patients with type 2 diabetes have an impaired response to GIP, while intravenous GLP-1 has been shown to increase insulin secretion in response to elevated glucose levels. Incretin-based agents include GLP-1 receptor agonists, which mimic endogenous GLP-1, and DPP-4 inhibitors (e.g., sitagliptin, vildagliptin, saxagliptin, alogliptin), which inhibit the breakdown of endogenous incretin hormones. GLP-1 receptor agonists stimulate insulin secretion in a glucose-dependent manner and suppress glucagon secretion with a low risk of hypoglycemia. The GLP-1 receptor agonists are further differentiated as either human analogues (e.g., liraglutide) or synthetic exendin-based mimetics (e.g., exenatide). These agents delay gastric emptying and may beneficially affect satiety and are thus associated with weight reduction.

CONCLUSION

GLP-1 receptor agonists and DPP-4 inhibitors facilitate therapy intensification and achievement of established glycemic goals. They enhance postprandial and fasting glycemic control, and use may improve beta-cell function and possibly preserve beta-cell mass. GLP-1 receptor agonists may also have favorable effects on blood pressure. They may be introduced as adjuncts to ongoing therapy with conventional agents with a potential benefit of slowing the progression of type 2 diabetes.

Present and Prospective Pharmacotherapy for the Management of Patients with Type 2 Diabetes

Diabetes Mellitus is a chronic condition prevalent worldwide. Type 2 diabetes is the most common form of diabetes, comprising 90% to 95% of all cases. Over the last few decades, the importance of glycemic control and its impact on prevention of diabetes-related complications has been documented in multiple clinical trials. As most patients with type 2 diabetes will require pharmacologic intervention to achieve and maintain appropriate glycemic control, new medications targeting different aspects of the pathophysiology of type 2 diabetes have been a significant focus of research and development. During the last decade, multiple new medications for diabetes management have become available: these medications have novel mechanisms of action, differences in effectiveness, and varying side effect profiles which will be reviewed in this article. Some of these newer medications, such as the GLP-1 analogues and DPP-4 inhibitors, have become widely accepted as therapeutic options for the management of type 2 diabetes.Additional classes of glucose-lowering medications are expected to become available in the near future. This manuscript will summarize available data regarding these newer and prospective medications for the management of type 2 diabetes.

Oral antidiabetic drug metabolism: pharmacogenomics and drug interactions

BACKGROUND

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

METHODS

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

RESULTS/CONCLUSION

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