Effect of exenatide on the pharmacokinetics and pharmacodynamics of warfarin in healthy Asian men

Drug-Drug Interactions Between Glucagon-Like Peptide 1 Receptor Agonists and Oral Medications: A Systematic Review

BACKGROUND

Glucagon-like peptide 1 receptor agonists (GLP1RAs) are used in the treatment of diabetes and obesity. Their slowing effect of gastric emptying might change oral drug absorption, potentially affecting pharmacokinetics, particularly in the case of medications with a narrow therapeutic index.

PURPOSE

The purpose of this systematic review is to summarize data on drug-drug interactions between GLP1RAs and oral drugs.

DATA SOURCES

The PubMed and EMBASE databases were searched up to November, 1st 2023.

STUDY SELECTION

We selected pharmacokinetic studies of any injectable GLP1RA given with an oral medication, and product prescribing sheets reporting data without access to the original study.

DATA EXTRACTION

Two authors independently extracted the data.

DATA SYNTHESIS

Twenty-two reports and six prescribing sheets were included. Treatment with GLP1RAs resulted in unaffected or reduced Cmax and delayed tmax of drugs with high solubility and permeability (warfarin, contraceptive pills, acetaminophen), drugs with high solubility and low permeability (angiotensin converting enzyme inhibitors), drugs with low solubility and high permeability (statins) and drugs with low solubility and permeability (digoxin). However, the use of GLP1RAs did not exert clinically significant changes in the AUC or differences in clinically relevant endpoints.

LIMITATIONS

The major limitations of the studies that are included in this systematic review are the enrollment of healthy subjects and insufficient data in conditions that might affect pharmacokinetics (e.g., kidney dysfunction).

CONCLUSIONS

To conclude, reduced Cmax and delayed tmax of drugs co-administered with GLP1RAs are consistent with the known delayed gastric output by the latter. Nevertheless, the overall drug exposure was not considered clinically significant. Dose adjustments are probably not required for simultaneous use of GLP1RAs with oral medications. Still, results should be carefully generalized to cases of background kidney dysfunction or when using drugs with narrow therapeutic index. The study is registered in PROSPERO: https://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD42022332339 .

Effects of GLP-1 and Its Analogs on Gastric Physiology in Diabetes Mellitus and Obesity

The processing of proglucagon in intestinal L cells results in the formation of glucagon, GLP-1, and GLP-2. The GLP-1 molecule becomes active through the effect of proconvertase 1, and it is inactivated by dipeptidyl peptidase IV (DPP-IV), so that the half-life of endogenous GLP-1 is 2-3 min. GLP-1 stimulates insulin secretion from β cells in the islets of Langerhans. Human studies show that infusion of GLP-1 results in slowing of gastric emptying and increased fasting and postprandial gastric volumes. Retardation of gastric emptying reduces postprandial glycemia. Exendin-4 is a peptide agonist of the GLP-1 receptor that promotes insulin secretion. Chemical modifications of exendin-4 and GLP-1 molecules have been accomplished to prolong the half-life of GLP-1 agonists or analogs. This chapter reviews the effects of GLP-1-related drugs used in treatment of diabetes or obesity on gastric motor functions, chiefly gastric emptying. The literature shows that diverse methods have been used to measure effects of the GLP-1-related drugs on gastric emptying, with most studies using the acetaminophen absorption test which essentially measures gastric emptying of liquids during the first hour and capacity to absorb the drug over 4-6 h, expressed as AUC. The most valid measurements by scintigraphy (solids or liquids) and acetaminophen absorption at 30 or 60 min show that GLP-1-related drugs used in diabetes or obesity retard gastric emptying, and this is associated with reduced glycemia and variable effects on food intake and appetite. GLP-1 agonists and analogs are integral to the management of patients with type 2 diabetes mellitus and obesity. The effects on gastric emptying are reduced with long-acting preparations or long-term use of short-acting preparations as a result of tachyphylaxis. The dual agonists targeting GLP-1 and another receptor (GIP) do not retard gastric emptying, based on reports to date. In summary, GLP-1 agonists and analogs are integral to the management of patients with type 2 diabetes mellitus and obesity, and their effects are mediated, at least in part, by retardation of gastric emptying.

Effect of Oral Semaglutide on the Pharmacokinetics of Lisinopril, Warfarin, Digoxin, and Metformin in Healthy Subjects

Background

Oral semaglutide is a tablet co-formulation of the human glucagon-like peptide-1 (GLP-1) analog semaglutide with the absorption enhancer sodium N-(8-[2-hydroxybenzoyl] amino) caprylate (SNAC). The absorption of coadministered oral drugs may be altered due to enhancement by SNAC, potential gastric emptying delay by semaglutide, or other mechanisms. Two one-sequence crossover trials investigated the effect of oral semaglutide on the pharmacokinetics of lisinopril, warfarin, digoxin, and metformin.

Methods

In trial 1, 52 healthy subjects received lisinopril (20 mg single dose) or warfarin (25 mg single dose) with subsequent coadministration with SNAC alone (300 mg single dose), followed by oral semaglutide 20 mg once daily (steady state). In trial 2, 32 healthy subjects received digoxin (500 μg single dose) or metformin (850 mg twice daily for 4 days), with subsequent coadministration with SNAC alone followed by oral semaglutide, as in trial 1.

Results

There were no apparent effects of oral semaglutide on area under the plasma concentration–time curve (AUC) and maximum plasma concentration (C_max) for lisinopril, warfarin, and digoxin. The AUC of metformin was increased by 32% (90% confidence interval 1.23–1.43) by oral semaglutide coadministration versus metformin alone, whereas the C_max was unaffected. SNAC alone did not affect exposure of lisinopril, warfarin, digoxin, or metformin. Adverse events were in line with those previously observed for GLP-1 receptor agonists.

Conclusions

Oral semaglutide or SNAC alone did not appear to affect the exposure of lisinopril, warfarin, or digoxin, and, based on its wide therapeutic index, the higher metformin exposure with oral semaglutide was not considered clinically relevant.

Electronic supplementary material

The online version of this article (10.1007/s40262-019-00756-2) contains supplementary material, which is available to authorized users.

Suppression Failure of Cortisol Secretion by Dexamethasone May Occur in Glucagon-like Peptide-1 Receptor Agonist-treated Patients with Diabetic Autonomic Neuropathy

Two diabetic women (case 1, 75 years old; case 2, 49 years old) being treated with glucagon-like peptide-1 (GLP-1) receptor agonists (GLP-1 RAs) showed no suppression of cortisol secretion on a dexamethasone suppression test (DST). However, its secretion was suppressed after switching from GLP-1 RAs to insulin. We also checked the cortisol secretion by a DST in five consecutive inpatients (case 3-7) being treated with GLP-1 RAs. The coefficients of R-R interval variation at rest and during deep breathing were lower in the two false-positive cases (case 1 and 2) than in the five true-negative cases (case 3-6). GLP-1 RAs can be switched to insulin in order to eliminate the slow absorption effect of dexamethasone by GLP-1 RAs if a DST is planned in diabetic patients receiving GLP-1 RAs.

Unexpected bleeding after Exenatide treatment: a causative relationship or a coincidence?

OBJECTIVES

Diabetes mellitus is an endemic disease of the current era. It is important to treat it properly. All antidiabetic medications have side effects and various safety profiles.

CASE REPORT

Fifty-two years old patient with type II diabetes mellitus, who had spontaneous cutaneous and intra muscular bleeding after starting treatment with Exenatide. The patient's history did not include any kind of spontaneous bleeding. Investigations did not reveal abnormal platelets count and function or coagulation profile. The use of the Exenatide was discontinued and during one year of follow-up, the patient did not experience an additional occurrence of spontaneous bleeding.

CONCLUSIONS

To the best of our knowledge, this is the first report of spontaneous bleeding probably caused by Exenatide. The exact pathophysiology, by which the drug can cause spontaneous bleeding, is still not clear and has to be revealed.

Pharmacokinetic drug evaluation of exenatide for the treatment of type 2 diabetes

INTRODUCTION

Glucagon-like peptide-1 (GLP-1) receptor analogs are a group of therapeutic agents which mimic endogenous GLP-1, exerting their effect by the stimulation of the GLP-1 receptor with a wide distribution. Its activation increases insulin releasing dependent on blood glucose levels, suppression of glucagon secretion and a reduction of hepatic glucose output. It delays gastric emptying and increases satiety. Exenatide is the synthetic version of exendin-4, a natural peptide with similar properties to human GLP-1. There are two pharmaceutical forms, for subcutaneous injection: twice daily and once weekly. Clinical practice guidelines recommend them because of a high efficacy reducing hyperglycemia, low risk of hypoglycemia and a significative weight loss effect. Gastrointestinal adverse events are the most common beside injection site-related. Their cost is the main limitation to use. Areas covered: We review the recent literature investigating the pharmacokinetics and pharmacodynamics and efficacy-safety studies of exenatide twice daily and once weekly in type 2 diabetes Expert opinion: GLP-1 receptor analogs are now positioned as an effective and safe drug for the treatment of type 2 diabetes. Exenatide significally reduces HbA1c and fasting plasma glucose. Additionally, it produces moderate weight loss and decreases blood pressure. One weekly formulation may improve compliance while cost is still a limitation. EXSCEL trial has shown that, despite cardiovascular safety, exenatide do not exhibits cardiovascular benefits.

Potential Underprediction of Warfarin Drug Interaction From Conventional Interaction Studies and Risk Mitigation: A Case Study With Epacadostat, an IDO1 Inhibitor

Drug-drug interaction (DDI) studies involving warfarin are typically conducted with subtherapeutic doses of warfarin to ensure the safety of volunteers. However, this approach may potentially have a systemic bias of underestimating pharmacodynamic (PD) DDI effect on warfarin at therapeutic levels of anticoagulation. We demonstrate here the utility of model-based DDI prediction for a clinically relevant warfarin regimen, using the example of epacadostat (INCB024360), the first-in-class indoleamine 2,3-dioxygenase 1 inhibitor in clinical development as a novel orally active immuno-oncological therapy. Observed data from a dedicated clinical DDI study using subtherapeutic warfarin suggested warfarin pharmacokinetics (PK), but not PD (anticoagulation), was significantly affected by concomitant epacadostat. However, subsequent PK/PD modeling and simulations indicated a clinically important DDI effect on warfarin PD at a higher baseline of the international normalization ratio (INR) and enabled recommendation of warfarin dose adjustment that is dependent on epacadostat dosing regimen and target INR.

Effect on the Gastrointestinal Absorption of Drugs from Different Classes in the Biopharmaceutics Classification System, When Treating with Liraglutide

Like other GLP-1 receptor agonists used for treatment of type 2 diabetes, liraglutide delays gastric emptying. In this clinical absorption study, the primary objective was to investigate the effect of liraglutide (at steady state) on the rate and/or extent of gastrointestinal (GI) absorption of concomitantly orally taken drugs from three classes of the Biopharmaceutics Classification System (BCS). To provide a general prediction on liraglutide drug-drug absorption interaction, single-dose pharmacokinetics of drugs representing BCS classes II (low solubility-high permeability; atorvastatin 40 mg and griseofulvin 500 mg), III (high solubility-low permeability; lisinopril 20 mg), and IV (low solubility-low permeability; digoxin 1 mg) were studied in healthy subjects at steady state of liraglutide 1.8 mg, or placebo, in a two-period crossover design. With liraglutide, the oral drugs atorvastatin, lisinopril, and digoxin showed delayed tmax (by ≤2 h) and did not meet the criterion for bioequivalence for Cmax (reduced Cmax by 27-38%); griseofulvin had similar tmax and 37% increased Cmax. Although the prespecified bioequivalence criterion was not met by all drugs, the overall plasma exposure (AUC) of griseofulvin, atorvastatin, lisinopril, and digoxin only exhibited minor changes and was not considered to be of clinical relevance.

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.

Exenatide twice daily: a review of its use in the management of patients with type 2 diabetes mellitus

Exenatide, administered subcutaneously twice daily (Byetta(®)), is a synthetic version of the natural peptide exendin-4, which is a glucagon-like peptide-1 (GLP-1) receptor agonist (incretin mimetic). Exenatide binds to the GLP-1 receptor with the same affinity as GLP-1, but has a much longer half-life, since it is not degraded by the enzyme dipeptidyl peptidase-4. Exenatide twice daily enhances glucose-dependent insulin secretion, suppresses inappropriately elevated glucagon secretion, slows gastric emptying and reduces caloric intake. In well-designed clinical trials, adjunctive subcutaneous exenatide 5 or 10 μg twice daily for 16-52 weeks significantly and dose-dependently improved glycaemic control and reduced mean body weight compared with placebo in patients with type 2 diabetes inadequately controlled with oral antihyperglycaemic drugs (OADs) and/or basal insulin. The improvements in glycaemic control and reductions in body weight were stably maintained during long-term therapy (up to 3.5 years). The efficacy of adjunctive exenatide twice daily was generally similar to that of basal, prandial or biphasic insulin, sulfonylureas, rosiglitazone and lixisenatide, and less than that of liraglutide, taspoglutide or exenatide once weekly with respect to reductions in glycated haemoglobin. Exenatide twice daily was generally well tolerated; mild to moderate nausea and vomiting, which decreased with time on therapy, were the most common adverse events. In patients not receiving concomitant sulfonylureas or insulin, the incidence of hypoglycaemia was low; when it did occur, it was generally mild in severity. Thus, adjunctive exenatide twice daily is a valuable option in the treatment of type 2 diabetes inadequately controlled with OADs and/or basal insulin.

The role of osteocalcin in human glucose metabolism: marker or mediator?

Increasing evidence supports an association between the skeleton and energy metabolism. These interactions are mediated by a variety of hormones, cytokines and nutrients. Here, the evidence for a role of osteocalcin in the regulation of glucose metabolism in humans is reviewed. Osteocalcin is a bone matrix protein that regulates hydroxyapatite size and shape through its vitamin-K-dependent, γ-carboxylated form. The concentration of osteocalcin in the circulation is a measure of bone formation. The undercarboxylated form of osteocalcin is active in glucose metabolism in mice. Total serum osteocalcin concentrations in humans are inversely associated with measures of glucose metabolism; however, human data are inconclusive with regard to the role of uncarboxylated osteocalcin in glucose metabolism because most studies do not account for the influence of vitamin K on the proportion of undercarboxylated osteocalcin or differentiate between the total and uncarboxylated forms of osteocalcin. Furthermore, most human studies do not concomitantly measure other bone turnover markers to isolate the role of osteocalcin as a measure of bone formation from its effect on glucose metabolism. Carefully designed studies are required to define the role of osteocalcin and its carboxylated or undercarboxylated forms in the regulation of glucose metabolism in humans.

GLP-1 agonists for type 2 diabetes: pharmacokinetic and toxicological considerations

INTRODUCTION

Within recent years, glucagon-like peptide 1 receptor agonists (GLP-1-RA) have emerged as a new treatment option for type 2 diabetes. The GLP-1-RA are administered subcutaneously and differ substantially in pharmacokinetic profiles.

AREAS COVERED

This review describes the pharmacokinetics and safety aspects of the currently available GLP-1 receptor agonists, liraglutide (based on the structure of native GLP-1), exenatide twice daily and exenatide once weekly (based on exendin-4) in relation to the kinetics and toxicology of native GLP-1. The review is based on electronic literature searches and legal documents in the form of assessment reports from the European Medicines Agency and the United States Food and Drug Administration.

EXPERT OPINION

GLP-1-based therapy combines several unique mechanisms of action and have the potential to gain widespread use in the fight against diabetes and obesity. The difference in chemical structure have strong implications for key pharmacokinetic parameters such as absorption and clearance, and eventually the safety and efficacy of the individual GLP-1-RA. The main safety concerns are pancreatitis and neoplasms, for which there are no identifiable differences in risk between the available agents. Antibody formation and injection site reactions are more frequent with the exendin-4-based compounds. The efficacy with regard to Hb(A1c) reduction is superior with the longer-acting agonists, whereas the shorter-acting GLP-1-RA seems to provide greater postprandial glucose control and lower tolerability as a possible consequence of less induction of tachyphylaxis. The future place of these agents will depend on the added safety and efficacy data in the several ongoing cardiovascular outcome trials.

Drug-drug interactions with glucagon-like peptide-1 receptor agonists

OBJECTIVE

To review drug interaction studies of glucagon-like peptide-1 receptor agonists (GLP-1RAs) and concurrent oral medications.

DATA SOURCES

PubMed was searched (to December 5, 2011) using the terms exenatide, liraglutide, albiglutide, and lixisenatide. The search was limited to studies published in English and conducted in adults. Abstracts from the American Diabetes Association Scientific Sessions from 2004 through 2011 were also searched.

STUDY SELECTION AND DATA EXTRACTION

All abstracts were screened for eligibility, which consisted of studies reporting the effects of GLP-1RA administration on the pharmacokinetics and pharmacodynamics of concurrent oral medications. Data extracted from eligible trials included study and population characteristics; pharmacokinetic parameters including maximum concentration (C(max)), time to maximum concentration (t(max)), and area under the concentration-time curve (AUC); and pharmacodynamic properties.

DATA SYNTHESIS

Our search identified 254 potentially relevant articles; of those, 11 articles evaluating 15 drug interactions were reviewed. Only 1 study was conducted in patients with type 2 diabetes. Equivalence in AUC was demonstrated in the majority of drug interactions studied (11 of 15). The AUCs of acetaminophen and lovastatin were decreased after exenatide administration and those of lisinopril and digoxin were decreased after liraglutide administration. In 10 studies, GLP-1RAs decreased the C(max) and, in 14 studies, prolonged the t(max) of study drug. Pharmacokinetic properties of drugs and differences in study design can explain differences in interaction potential.

CONCLUSIONS

GLP-1RAs may produce clinically significant interactions with drugs that require achievement of target peak concentrations or a rapid onset of action. Studies in patients with type 2 diabetes are needed to further assess and allow comparison of several GLP-1RA agents' impact on steady-state pharmacokinetics and pharmacodynamics of concomitant oral medications.

Effect of exenatide on the pharmacokinetics of a combination oral contraceptive in healthy women: an open-label, randomised, crossover trial

BACKGROUND

Consistent with its effect on gastric emptying, exenatide, an injectable treatment for type 2 diabetes, may slow the absorption rate of concomitantly administered oral drugs resulting in a decrease in maximum concentration (Cmax). This study evaluated the drug interaction potential of exenatide when administered adjunctively with oral contraceptives, given their potential concomitant use.

METHODS

This trial evaluated the effect of exenatide co-administration on single- and multiple-dose pharmacokinetics of a combination oral contraceptive (ethinyl estradiol [EE] 30 μg, levonorgestrel [LV] 150 μg [Microgynon 30®]). Thirty-two healthy female subjects participated in an open-label, randomised, crossover trial with 3 treatment periods (oral contraceptive alone, 1 hour before exenatide, 30 minutes after exenatide). Subjects received a single dose of oral contraceptive on Day 8 of each period and QD doses on Days 10 through 28. During treatment periods of concomitant usage, exenatide was administered subcutaneously prior to morning and evening meals at 5 μg BID from Days 1 through 4 and at 10 μg BID from Days 5 through 22. Single- (Day 8) and multiple-dose (Day 22) pharmacokinetic profiles were assessed for each treatment period.

RESULTS

Exenatide did not alter the bioavailability nor decrease daily trough concentrations for either oral contraceptive component. No substantive changes in oral contraceptive pharmacokinetics occurred when oral contraceptive was administered 1 hour before exenatide. Single-dose oral contraceptive administration 30 minutes after exenatide resulted in mean (90% CI) Cmax reductions of 46% (42-51%) and 41% (35-47%) for EE and LV, respectively. Repeated daily oral contraceptive administration 30 minutes after exenatide resulted in Cmax reductions of 45% (40-50%) and 27% (21-33%) for EE and LV, respectively. Peak oral contraceptive concentrations were delayed approximately 3 to 4 hours. Mild-to-moderate nausea and vomiting were the most common adverse events observed during the trial.

CONCLUSIONS

The observed reduction in Cmax is likely of limited importance given the unaltered oral contraceptive bioavailability and trough concentrations; however, for oral medications that are dependent on threshold concentrations for efficacy, such as contraceptives and antibiotics, patients should be advised to take those drugs at least 1 hour before exenatide injection.

TRIAL REGISTRATION

ClinicalTrials.gov: NCT00254800.

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.

The Clinical Efficacy and Safety of Glucagon-Like Peptide-1 (GLP-1) Agonists in Adults with Type 2 Diabetes Mellitus

Objective:

To review the efficacy and safety of glucagon-like peptide-1 (GLP-1) agonists to determine their role in type 2 diabetes mellitus (T2DM).

Data sources:

A Medline search was conducted using the keywords exenatide, liraglutide, glucagon-like peptide-1, type 2 diabetes mellitus, hyperglycemia, pharmacokinetics, pharmacology and safety.

Study selection:

All identified articles written in English were evaluated with priority given to controlled, randomized trials including human data. References of identified published trials were reviewed for additional trials to be included in the review.

Data synthesis:

Exenatide and liraglutide are GLP-1 agonists approved for the treatment of T2DM. Several randomized, active and placebo controlled trials examining the efficacy and safety of exenatide and liraglutide both as monotherapy and in combination therapy have been conducted. Both agents have demonstrated improved glycemic control in addition to weight loss and increased beta-cell function. The most common adverse effects are gastrointestinal in nature and appear to be transient.

Conclusion:

It appears exenatide and liraglutide are safe and effective in the treatment of T2DM and may exhibit effects that make them preferred over other anti-diabetic medications.

Pharmacological management of type 2 diabetes: the potential of incretin-based therapies

Management guidelines recommend metformin as the first-line therapy for most patients with type 2 diabetes uncontrolled by diet and exercise. Efficacy with metformin therapy is usually of limited duration, which necessitates the early introduction of one or two additional oral agents or the initiation of injections, glucagon-like peptide-1 (GLP-1) agonists or insulin. Although safe and effective, metformin monotherapy has been associated with gastrointestinal side effects (≈20% of treated patients in randomized studies) and is contraindicated in patients with renal insufficiency or severe liver disease. Patients treated with a sulphonylurea are at increased risk for hypoglycaemia and moderate weight gain, whereas those receiving a thiazolidinedione are subject to an increased risk of weight gain, oedema, heart failure or fracture. Weight gain and hypoglycaemia are associated with insulin use. Thus, there is an unmet need for a safe and efficacious add-on agent after initial-therapy failure. Evidence suggests that incretin-based agents, such as GLP-1 receptor agonists and dipeptidyl peptidase-4 inhibitors, can successfully achieve glycaemic targets and potentially provide cardiovascular and β-cell-function benefits. This review will examine current approaches for treating type 2 diabetes and discuss the place of incretin therapies, mainly GLP-1 agonists, in the type 2 diabetes treatment spectrum.

Incretin-based therapies for type 2 diabetes mellitus: current status and future prospects

Incretin-based therapies encompass two new classes of antidiabetic drugs: glucagon-like peptide-1 (GLP-1) receptor agonists (e.g., liraglutide, exenatide, and exenatide long-acting release), which are structurally related to GLP-1, and the dipeptidyl peptidase-4 (DPP-4) inhibitors (e.g., sitagliptin and saxagliptin), which limit the breakdown of endogenous GLP-1. To evaluate the safety and effectiveness of incretin-based therapies for the treatment of type 2 diabetes mellitus and the role of these therapies in clinical practice, a MEDLINE search (January 1985-November 2009) was conducted. Relevant references from the publications identified were also reviewed. Of 28 studies identified, 22 were randomized controlled trials. Data show that these therapies affect insulin secretion in a glucose-dependent manner, achieving clinically meaningful reductions in hemoglobin A(1c) levels, with very low rates of hypoglycemia. In addition, reductions in body weight have been observed with GLP-1 receptor agonists, which also exert a pronounced effect on systolic blood pressure. Various human and animal studies show that GLP-1 improves beta-cell function and increases beta-cell proliferation in vitro, which may slow disease progression. Thus, incretin-based therapies represent a promising addition to the available treatments for type 2 diabetes.

The safety and tolerability of GLP-1 receptor agonists in the treatment of type-2 diabetes

Established therapies for type-2 diabetes effectively reduce blood glucose, but are often associated with adverse effects that pose risks to patient's health or diminish adherence to treatment. Weight gain, hypoglycaemia and gastrointestinal symptoms are commonly reported and some agents may not be safe for use in patients with renal impairment or elevated cardiovascular risk. New treatments based on the action of the endogenous human hormone glucagon-like peptide-1 (GLP-1), including exenatide and liraglutide, are available. These therapies provide a novel pharmacological approach to glycaemic control via multiple mechanisms of action, and accordingly exhibit different safety and tolerability profiles than conventional treatments. GLP-1 receptor agonists stimulate insulin release only in the presence of elevated blood glucose and are therefore associated with a fairly low risk of hypoglycaemia. Gastrointestinal symptoms are common but transient, and there appears to be little potential for interaction with other drugs. GLP-1 receptor agonists are associated with weight loss rather than weight gain. As protein-based therapies, these agents have the potential to induce antibody formation, but the impact on efficacy and safety is minor. GLP-1 receptor agonists thus offer a new and potentially useful option for clinicians concerned about some of the common adverse effects of type-2 diabetes therapies.

Effect of single-dose rifampin on the pharmacokinetics of warfarin in healthy volunteers

Based on in vitro rat and human hepatocyte uptake studies showing inhibition of warfarin uptake in the presence of the nonspecific organic anion-transporting polypeptide (OATP) inhibitor rifampin, a clinical study was conducted in 10 healthy volunteers to examine the in vivo relevance of OATP hepatic uptake on the pharmacokinetics of warfarin. In a randomized, single-dose, two-period, crossover design, subjects received a 7.5-mg dose of warfarin, either alone or immediately following a 600-mg intravenous dose of rifampin. Rifampin did not significantly alter the R- or S-warfarin area under the concentration-time curves (AUCs) from 0 to 12 h (period of hepatic OATP inhibition by rifampin) or the maximum plasma concentration (C(max)) value. AUC(0-∞) was decreased on days rifampin was administered, for both R-warfarin (25% reduction; P < 0.001) and S-warfarin (15% reduction; P < 0.05). No differences were seen in the area under the international normalized ratio (INR)-time curve. Our study suggests that hepatic uptake via OATPs may not be clinically important in the pharmacokinetics of warfarin.

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.

Ethnic differences in the population pharmacokinetics and pharmacodynamics of warfarin

Ethnic differences in warfarin maintenance doses have been documented amongst the three major Asian ethnic groups (Chinese, Malay and Indian) in Singapore. Studies have shown that cytochrome P450 2C9 (CYP2C9) polymorphisms alone did not entirely account for these differences. Recent reports suggest that VKORC1 (subunit of vitamin K epoxide reductase) haplotypes are more predictive of warfarin response. Population pharmacokinetic/pharmacodynamic (PK/PD) modelling techniques were employed to characterise the PK and PD of warfarin in a healthy volunteer study of 16 Chinese and Indian subjects following a single 25 mg dose of warfarin. To further investigate the underlying differences in warfarin response, a semi-mechanistic modelling approach (using an indirect response model for PCA activity) incorporating the vitamin K cycle was attempted using population methods with Bayesian inference. All eight Indian subjects had H7H7 VKORC1 haplotypes and three had either *2/wt or *3/wt CYP2C9 genotypes. Six Chinese subjects had H1H1 VKORC1 haplotypes and one had H1H7. All Chinese subjects were homozygous wt/wt for CYP2C9. Simulations to steady state were performed to examine warfarin response in subjects with different CYP2C9 and VKORC1 polymorphisms. The presence of a single *2 or *3 CYP2C9 allele reduced mean [SE (standard error)] S-warfarin clearance by 35% from 0.276 (0.04) to 0.180 (0.11) l/h. Subjects with VKORC1 haplotype groups of H7H7 had increased mean (SE) C (50,S) (concentration of S-warfarin required to achieve 50% of maximum effect) of 479 (7.3) compared to 206 (6.7) ng/ml in subjects with the H1H1 groups. For subjects with the H1H7 haplotype, mean (SE) C (50,S) increased 1.4 times to 288 (1.3) ng/ml compared to subjects with H1H1 haplotypes. Steady state simulations showed that whilst CYP2C9 polymorphisms affect the PK of warfarin, VKORC1 haplotypes may be better predictors of warfarin response. Since 90% of Chinese subjects had the VKORC1 H1 haplotype and 100% of Indian subjects the H7 haplotype in this study, ethnic differences in warfarin response in this study appear to be linked to differences in VKORC1 haplotypes.

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.

A review of exenatide as adjunctive therapy in patients with type 2 diabetes

Background

Incretin glucagon-like peptide-1 (GLP-1) is a hormone released from cells in the gastrointestinal tract (GI), leading to glucose-dependent insulin release from the pancreas. It also suppresses postprandial hyperglycemia, glucagon secretion and slows gastric emptying. Exenatide (EXE), a functional analog of human GLP-1, was approved by the US FDA in April 2005.

Objective

This article reviews current primary literature on the clinical efficacy and safety of EXE in the treatment of type 2 diabetes mellitus (DM) and describes the pharmacokinetics, pharmacodynamics, dosing and administration of EXE.

Methods

English-language articles were identified through a search of MEDLINE (1966 to March 2009), International Pharmaceutical Abstracts (1970 to present), and Cochrane Database of Systemic Reviews (1995 to March 2009). Search terms included EXE, diabetes mellitus, postprandial hyperglycemia, gastric emptying, glucagon, pharmacokinetics and pharmacodynamics. Articles were selected for review if their designs were randomized, blinded and of controlled design that focused on clinical outcomes of patients with type 2 DM.

Results

EXE is administered subcutaneously in the thigh, abdomen or upper arm within the 60-minute period before the morning and evening meals. Its C_max is reached within 2.1 hours, and its T_1/2 in 2.4 hours. EXE’s metabolism is primarily through the kidneys. For the patients who received EXE 10 μg SC BID in three, 30-week, placebo-controlled studies with background sulfonylureas (SUs), metformin (MET), or SU + MET, there were significant reductions in HbA_1c (0.77 to 0.86%), fasting plasma glucose (0.6 mmol/L) and body weight (1.6 to 2.8 kg) (P ≤ 0.05 vs PCB) that were sustained in patients who completed two open-label phase trials with an additional 52 weeks of therapy. The use of thiazolidinediones was associated with a slight advantage over EXE in improving HbA_1c along with increased weight gain; those who received EXE lost weight, but experienced more GI adverse effects. Patients who received EXE lost significant body weight while patients who received insulin gained weight. Patients receiving insulin had lower fasting, prelunch and predinner glucose excursions while patients in the EXE groups had lower postprandial glucose levels. Nausea was most frequently (>20%) reported in patients receiving the highest dose of EXE (10 μg SC BID vs 5 μg SC BID).

Conclusions

EXE at the dose of 10 μg SC BID has been proven to decrease HbA_lc by 1.3% ± 0.1% and decrease body weight by up to 5.3 ± 0.8 kg at week 82. Nausea was the most frequently reported adverse event (>20%) especially in patients being treated with EXE 10 μg SC BID. EXE can be safely added to MET therapy, SU therapy or MET + SU combination to effectively target glycemic goals in patients with type 2 DM. Long-term, head-to-head studies assessing the effect of the EXE ± oral agents/insulins in patients with HbA_lc ≥ 10% are still needed to fully clarify the role of EXE in poorly controlled patients with type 2 DM.

Influence of laropiprant, a selective prostaglandin D2 receptor 1 antagonist, on the pharmacokinetics and pharmacodynamics of warfarin

Laropiprant (LRPT), a prostaglandin D2 receptor 1 antagonist shown to reduce niacin-induced flushing symptoms, is being developed in combination with niacin for the treatment of dyslipidemia. This study assessed the pharmacokinetics/pharmacodynamics of single-dose warfarin in the presence/absence of multiple-dose LRPT. Thirteen subjects received 2 treatments in random order separated by > or =10-day washout: (1) multiple-dose LRPT 40 mg/d for 12 days (days -5 to 7) with coadministered single-dose warfarin 30 mg (day 6) and (2) single-dose warfarin 30 mg (day 1). R+- and S(-)-warfarin and international normalized ratio (INR) were assayed predose and up to 168 hours postdose. Comparability was declared if the 90% confidence intervals (CIs) for the geometric mean ratio (GMR; warfarin + LRPT/warfarin alone) of area under the plasma concentration curve from zero to infinity (AUC0-infinity) for R+- and S(-)-warfarin were contained within (0.80, 1.25). The estimated GMRs of AUC0-infinity (90% CIs) were 1.02 (0.96, 1.09) and 1.04 (0.98, 1.09) for R+- and S(-)-warfarin, respectively. The estimated GMRs of maximum plasma concentration (Cmax) (90% CIs) were 1.13 (1.02, 1.26) and 1.11 (0.99, 1.24) for R+- and S(-)-warfarin, respectively. The estimated GMRs of area under the prothrombin time INR curve from 0 to 168 hours on day 21 (INR AUC0-168 h) and average maximum observed prothrombin time INR (INRmax) were 1.02 (0.99, 1.05) and 1.04 (0.98, 1.10), respectively. There was no evidence of clinically meaningful alterations in the pharmacokinetics and pharmacodynamics (ie, INR) of R(+)- or S(-)-warfarin after coadministration of multiple-dose LRPT and single-dose warfarin.

Efficacy and safety of exenatide in patients of Asian descent with type 2 diabetes inadequately controlled with metformin or metformin and a sulphonylurea

AIMS

To evaluate the efficacy of exenatide in Asian patients with type 2 diabetes (T2D) inadequately controlled with oral agents.

METHODS

Patients taking metformin (MET) alone or with a sulphonylurea (SU) were randomly assigned to exenatide 5 microg then 10 microg twice-daily for 4 and 12 weeks, respectively, or placebo. The primary endpoint was baseline to endpoint HbA(1c) change.

RESULTS

466 patients (age 54+/-9 years, weight 68.7+/-11.2 kg, BMI 26.3+/-3.3 kg/m(2), and HbA(1c) 8.3+/-1.1%; mean+/-S.D.) were enrolled in the full analysis set. Endpoint HbA(1c) reduction (mean [95% CI]) with exenatide was superior to placebo (-1.2 [-1.3, -1.1]% vs. -0.4 [-0.5, -0.2]%, p<0.001). More exenatide- than placebo-treated patients achieved HbA(1c) <or=7% (48% vs. 17%, p<0.001). At endpoint, weight reduction was greater with exenatide (-1.2 [-1.5, -0.9]kg) than placebo (-0.1 [-0.3, 0.2]kg), p<0.001. Nausea, generally mild-to-moderate, was the most common adverse event with exenatide (25% vs. 1% with placebo). The incidence of symptomatic hypoglycaemia with exenatide and placebo were 36% and 9%, respectively (p<0.001). Hypoglycaemia rates (events/patient-year) for patients taking exenatide with MET or MET and SU were 1.8 (0.9, 3.7) and 4.7 (3.5, 6.5), respectively.

CONCLUSION

Exenatide treatment improved glycaemic control in Asian patients with T2D and had a similar safety profile as in non-Asian patients.

Influence of taranabant, a cannabinoid-1 receptor inverse agonist, on pharmacokinetics and pharmacodynamics of warfarin

INTRODUCTION

The pharmacokinetic/pharmacodynamic effects of warfarin were assessed in the presence and absence of taranabant, an orally active, highly selective, potent, cannabinoid-1 receptor inverse agonist, which was being developed for the treatment of obesity.

METHODS

Twelve subjects were assigned to two open-label treatments in fixed sequence separated by a 14-day washout. Treatment A was single-dose warfarin 30 mg on day 1. Treatment B was multiple-dose taranabant 6 mg each day for 21 days (days -14 to day 7) with coadministration of singledose warfarin 30 mg on day 1. Blood samples were collected predose and up to 168 hours postdose for assay of R(+)-and S(-)-warfarin and prothrombin time/international normalized ratio (PT/INR).

RESULTS

The geometric mean ratios (GMR; warfarin+taranabant/warfarin 90% confidence interval [CI] primary endpoints) for area under the curve (AUC)(0-infinity) for R(+)-and S(-)-warfarin were 1.10 (90% CI: 1.03, 1.18) and 1.06 (90% CI: 1.00, 1.13), respectively. The GMRs (warfarin+taranabant/warfarin) for the maximum plasma concentration (C(max)) of S(-)-and R(+)-warfarin were 1.16 (90% CI: 1.05, 1.28) and 1.17 (90% CI: 1.07, 1.29), respectively. For R(+)-and S(-)-warfarin, the 90% CIs for AUC(0-infinity) GMRs fell within the prespecified bounds. Taranabant did not produce a clinically meaningful effect on PT/INR.

CONCLUSION

No clinically significant alterations of the pharmacokinetics of R(+)-and S(-)-warfarin were seen following coadministration of multipledose taranabant 6 mg and single-dose warfarin 30 mg.

Exenatide: incretin therapy for patients with Type 2 diabetes mellitus

Exenatide is the first in a novel class of drugs that mimics naturally occurring glucagon-like peptide 1. In patients with Type 2 diabetes mellitus (T2DM), control of both glycemia and bodyweight are important to minimize the risk of diabetes complications. Exenatide improves glycemic control through glucose-dependent insulin secretion, suppression of glucagon secretion, delaying gastric emptying and suppressing appetite. Exenatide therapy significantly reduced glycated hemoglobin (Hb_A1c) and fasting and postprandial plasma glucose when added to metformin and/or sulfonylureas, with an average weight loss of 2 kg. Furthermore, exenatide-treated patients sustained the reductions achieved in Hb_A1c at 12 weeks with a progressive reduction in bodyweight during 3-year follow-up. Exenatide is generally well tolerated; nausea is the most common side effect but significantly reduces over time and with gradual dose titration. Hypoglycemia at a rate greater than placebo only occurred in combination with sulfonylureas. Exenatide may enable patients with T2DM to improve glycemic control while reducing the risk of hypoglycemia and provoking weight loss.

Exenatide

Exenatide is the first in a new class of compounds, which possess similar activity to the naturally-occurring hormone glucagon-like peptide-1 (GLP-1). It mirrors many of the effects of GLP-1, improving glycaemic control through a combination of mechanisms, which include glucose-dependent stimulation of insulin secretion, suppression of glucagon secretion, slowing of gastric emptying and reduced appetite. Phase III clinical trials showed exenatide therapy for 30 weeks significantly reduced glycated haemoglobin, and fasting and postprandial plasma glucose compared with baseline when added to metformin and sulfonylureas or a combination of the two, with an average weight loss of approximately 2 kg. Exenatide can also be used in combination with thiazolidinediones and may be an alternative to insulin in patients requiring additional therapy. In patients with established Type 2 diabetes, control of both glycaemia and body weight are important to minimise the risk of future diabetes complications. Open-label extensions from these pivotal trials demonstrate that patients treated with exenatide for < or = 3 years sustained the reductions in glycaemic control achieved at 30 weeks and had a progressive reduction in body weight. Exenatide is generally well tolerated; nausea is the most commonly reported side effect, but can be significantly reduced when a target dose of exenatide is achieved in patients with gradual dose titration. Hypoglycaemia has been encountered in clinical trials of exenatide, especially on initiation of therapy with sulfonylureas (not with metformin). Exenatide may enable patients with Type 2 diabetes to improve glycaemic control and reduce or eliminate the risk of hypoglycaemia and weight gain.

Safety and adverse effects associated with GLP-1 analogues

The incretin mimetics are an emerging class of agents for the treatment of diabetes. So far, exenatide is licensed for use in the US and also became available in the UK in May 2007. Within development and Phase III trials, liraglutide may also be made available within the next 2 years. These agents enhance glucose-dependent insulin secretion and exhibit other antihyperglycaemic actions, which are of particular benefit to overweight patients with Type 2 diabetes. This article reviews the profile of adverse effects for these agents in relation to their current (exenatide) and anticipated (liraglutide) role in the management of Type 2 diabetes.

Exenatide

Exenatide (Byetta) is a novel, synthetic, incretin mimetic, glucoregulatory peptide approved in the US and Europe for the treatment of patients with type 2 diabetes mellitus who have inadequate glycaemic control despite receiving treatment with maximum tolerated doses of metformin and/or a sulfonylurea. In randomised, controlled, phase III trials and post hoc completer analyses in this patient population, the addition of subcutaneous exenatide twice daily significantly improved glycaemic control and was associated with progressive and significant bodyweight reduction from baseline for up to 2 years. The overall intensity of glycaemic control with exenatide was similar to that achieved with once-daily insulin glargine or twice-daily biphasic insulin aspart. Exenatide was generally well tolerated. Most adverse events were mild to moderate in severity and gastrointestinal in nature. The overall rate of hypoglycaemia was similar to rates observed with placebo (when administered with metformin) and insulin comparators (when administered with metformin and a sulfonylurea). The addition of exenatide to therapy with metformin and a sulfonylurea provided significant improvements in treatment satisfaction and patients' health-related quality of life (HR-QOL). The drug was also cost effective compared with pioglitazone, glibenclamide (glyburide), insulin glargine (all in combination with metformin and/or a sulfonylurea) and metformin alone. Overall, adjunctive therapy with exenatide is a valuable therapeutic option in patients with type 2 diabetes requiring moderate improvements in glycaemic control despite treatment with metformin and/or a sulfonylurea.