Rhabdomyolysis caused by a potential sitagliptin-lovastatin interaction

Rosuvastatin-Induced Rhabdomyolysis as a Result of Drug Interaction With Sitagliptin: A Case Report

Rhabdomyolysis was not reported in clinical trials with Sitagliptin alone. However, several reports in the literature on rhabdomyolysis resulted from the interaction between statins and Sitagliptin. In patients with type 2 diabetes and hyperlipidemia, it is expected to co-prescribe statins and Sitagliptin. Herein, we report the case of a 64-year-old woman with rhabdomyolysis should be caused by a drug-drug interaction between Rosuvastatin and Sitagliptin. The patient denied any history of weakness or myalgia during past medical assessments.

Impact of metformin on statin-associated myopathy risks in dyslipidemia patients

A growing number of patients with metabolic disorders are receiving statin and antidiabetic therapies as comedications. A signal of increased risk of myotoxicity due to potential interactions between antidiabetics and statins has been detected in previous studies. To investigate the effects of metformin on myopathy risks when added to preexisting statin therapy in dyslipidemia patients, we performed a retrospective cohort study using the Korean national health insurance data in statin-treated dyslipidemia patients with or without concomitant metformin use. We compared the risk of myopathy in statin + metformin users against statin-only users. Hazard ratios (HRs) and 95% confidence intervals (CIs) have been calculated following propensity score (PS) matching between study groups and subsequent stratification per patient factors. We included 4092 and 8161 patients in PS-matched statin + metformin and statin-only groups, respectively. The risk of myopathy decreased when metformin was used together with statins (adjusted HR 0.84; 95% CI 0.71-0.99). In subgroup analyses per individual statin agent and in stratified risk analyses, no specific statin agents or patient factors were associated with statistically significant myopathy risk. This study found that a comedication with metformin was associated with decreased myopathy risk in statin-treated dyslipidemia patients compared to statin-only users. Our findings suggest that metformin may provide protective effects on potential muscle toxicities induced by statin therapy.

Case Report: Rhabdomyolysis secondary to vildagliptin overdose in a suicidal attempt: A case report and brief literature review

Rhabdomyolysis is a life-threatening syndrome associated with direct or indirect muscle damage that is rarely reported with dipeptidyl peptidase (DPP)-4 inhibitors. Here we presented a case in which a 58-year-old female suffered from severe swelling and pain in bilateral lower limbs and oliguria after a suicidal vildagliptin overdose. Drug-induced rhabdomyolysis and drug-induced liver injury were diagnosed based on laboratory and radiological findings. The patient was treated with fluid resuscitation, insulin, electrolyte replacement, diuretics, urine alkalizing agents, anticoagulants, antioxidants, and 24-h bedside ECG monitoring and suicide prevention. After 20 days of hospitalization and close monitoring, the patient was discharged without sequelae. Risk factors, diagnostic criteria, disease mechanisms, and outcomes were also discussed. This case illustrated that overdose of oral anti-diabetic medications may result in clinically significant adverse events, such as rhabdomyolysis in this case with a DPP-4 inhibitor. Although the incidence is low, special attention should be paid to intentional or accidental exposure to anti-diabetic medications during suicide attempts, especially in depressed patients with diabetes.

Prevalence and predictors of clinically significant statin-drug interactions among Yemeni patients taking statins for primary and secondary prevention of cardiovascular disease

BACKGROUND

Statins are extensively used in clinical practice for the primary and secondary prevention of cardiovascular diseases. Statins are usually taken in combination with other medications. This may increase the risk of statin-drug interactions. The study aimed to evaluate the prevalence, patterns, and predictors of clinically significant statin-drug interactions among patients on statin therapy.

MATERIAL AND METHODS

A cross-sectional study was conducted at the cardiology, endocrine, and internal medicine outpatient clinics in four tertiary care hospitals in Sana'a, Yemen. Lexicomp Drug Interaction database was used to analyze the prescriptions for potential statin-drug interactions. Binary and multivariable logistic regression were utilized for analysis.

RESULTS

Of the total number of patients (634), 114 individuals (18%) had a total of 122 statin-drug interactions. According to Lexicomp risk classification, 102 (83.6%) DDIs were class C (monitor therapy), 19 (15.6%) were class D (therapy modification), and only one (0.8%) class X (avoid combination). Simvastatin use was significantly associated with the presence of category D and X DDIs (15.9% vs. 1.6%, p < .001). Polypharmacy (OR = 2.571, p < .001) and having ≥3 comorbidities (OR = 2.512, p < .001) were the only variables associated with the presence of statin-drug interactions (C, D, and/or X).

CONCLUSION

Patients with polypharmacy and those with three or more comorbidities had a higher risk for statin-drug interactions. Therefore, routine screening by physicians and pharmacists for potential interactions should occur before prescribing or dispensing any medication to avoid clinically significant statin-drug interactions.

DPP-4 Inhibitors in Combination with Lipid-Lowering Agents and Risk of Serious Muscular Injury: A Nested Case-Control Study in a Nationwide Cohort of Patients with Type 2 Diabetes Mellitus

INTRODUCTION

After a safety warning was issued for a risk of muscular injury associated with dipeptidyl peptidase-4 (DPP-4) inhibitor use, especially when co-prescribed with statins, spontaneous reporting analyses provided conflicting results.

OBJECTIVE

The aim of this study was to investigate the association between DPP-4 inhibitor use and the risk of muscular injury in individuals with type 2 diabetes mellitus using statins or fibrates.

METHODS

We conducted a nested case-control study amongst a cohort of individuals with type 2 diabetes using statins or fibrates, identified from a nationwide French health insurance database (2009-2014). Cases of serious muscular injury were defined as subjects hospitalized for rhabdomyolysis or myopathy, or for whom testing for myoglobin or creatine phosphokinase followed by a change in statin or fibrate prescription (dose decrease, treatment switch, or stop) was identified. Up to ten controls were matched to each case according to sex, age, and type of lipid-lowering agent. Associations between DPP-4 inhibitor use and serious muscular injury were estimated using a multivariate conditional logistic regression model, providing odds ratios (ORs) adjusted for alcoholism, chronic renal failure, hypothyroidism, and number of concomitant drugs.

RESULTS

Within the 35,117 individuals with type 2 diabetes mellitus constituting the source cohort, 437 statin-user cases were identified who were matched to 4358 statin-user controls. Similarly, 54 fibrate-user cases were identified who were matched to 540 fibrate-user controls. The adjusted OR for DPP-4 inhibitor use and serious muscular injury was estimated at 1.0 (95% confidence interval [CI] 0.7-1.2) in statin users and 0.8 (95% CI 0.4-1.9) in fibrate users.

CONCLUSION

In this study, DPP-4 inhibitor use was not associated with an increased risk of serious muscular injury among patients with type 2 diabetes mellitus using statins or fibrates.

Myopathy with DPP-4 inhibitors and statins in the real world: investigating the likelihood of drug-drug interactions through the FDA adverse event reporting system

AIMS

To investigate the occurrence of myopathy with oral glucose-lowering drugs (OGLDs) and statins, with a focus on dipeptidyl peptidase-4 inhibitors (DPP4-is).

METHODS

The FDA adverse event reporting system (FAERS) was queried (2004-2016) to compare the proportion of adverse events with OGLDs, alone and in combination with statins, using the reporting odds ratio (ROR) with relevant 95% confidence interval (95%Cl), adjusted for sex, age and concomitant presence of other OGLDs/lipid-lowering drugs. Drug-drug interaction is claimed whenever the frequency of an event is enhanced by combination treatment. Consistency/robustness of findings was tested by applying additive/multiplicative models and accounting for competition bias (i.e., adverse events previously known to be associated with OGLDs were removed).

RESULTS

Over a 13-year period, we retrieved 142,888 cases of myopathy. The use of DPP4-is alone was not associated with higher reporting of myopathy (no. of cases = 4898; adjusted ROR = 1.00; 95%CI = 0.96-1.04), with the notable exclusion of vildagliptin (262; 1.64; 1.42-1.88). No increased occurrence emerged when used in combination with statins, with consistent findings from additive/multiplicative models for all DPP4-is. Likewise, no increased reporting was found for other OGLDs (28,964; 0.64; 0.62-0.67); data on the interaction with statins were consistent/robust across analyses only for sulfonylureas (the interaction is likely and biologically plausible) and sodium glucose cotransporter-2 inhibitors.

CONCLUSIONS

Real-world FAERS data do not raise concern for muscular toxicity with DPP4-is in combination with statins, making a drug interaction very unlikely.

Red Yeast Rice: A Systematic Review of the Traditional Uses, Chemistry, Pharmacology, and Quality Control of an Important Chinese Folk Medicine

Red yeast rice (RYR), a Chinese traditional folk medicine produced by the fermentation of cooked rice kernels with a Monascaceae mold, Monascus purpureus, has long been used to treat blood circulation stasis, indigestion, diarrhea, and limb weakness in East Asian countries. This article provides a systematic review of the traditional uses, chemistry, biological activities, and toxicology of RYR to highlight its future prospects in the field of medicine. The literature reviewed for this article was obtained from the Web of Science, Elsevier, SciFinder, PubMed, CNKI, ScienceDirect, and Google Scholar, as well as Ph.D. and M.Sc. dissertations, published prior to July 2019. More than 101 chemical constituents have been isolated from RYR, mainly consisting of monacolins, pigments, organic acids, sterols, decalin derivatives, flavonoids, polysaccharides, and other compounds. Crude extracts of RYR, as well as its isolated compounds, possess broad pharmacological properties with hypolipidemic, anti-atherosclerotic, anti-cancer, neurocytoprotective, anti-osteoporotic, anti-fatigue, anti-diabetic, and anti-hypertensive activities. However, further studies are needed to characterize its diverse chemical constituents and the toxicological actions of the main bioactive compounds. New pharmacological trials addressing the overlooked traditional uses of RYR, such as in the treatment of indigestion and diarrhea, are required.

Drug interactions of dipeptidyl peptidase 4 inhibitors involving CYP enzymes and P-gp efflux pump

Dipeptidyl peptidase 4 (DPP4) inhibitors are oral antidiabetic drugs approved to manage type 2 diabetes mellitus. Saxagliptin is a substrate of CYP3A4/5 enzymes while other DPP4 inhibitors such as sitagliptin, linagliptin, gemigliptin and teneligliptin are weak substrates of CYP3A4. DPP4 inhibitors have also been identified as substrates of P-gp. Hence, the drugs inhibiting or inducing CYP3A4/5 enzymes and/or P-gp can alter the pharmacokinetics of DPP4 inhibitors. This review is aimed to identify the drugs interacting with DPP4 inhibitors. The plasma concentrations of saxagliptin have been reported to be increased significantly by the concomitant administration of ketoconazole or diltiazem while no significant interactions between various DPP4 inhibitors and drugs like warfarin, digoxin or cyclosporine have been identified.

Sitagliptin and Simvastatin Interaction Causing Rhabdomyolysis and AKI

We report a case of rhabdomyolysis and severe acute kidney injury (AKI) requiring dialysis in a 69-year-old male who was recently started on sitagliptin while on chronic simvastatin therapy. This potential interaction is not included in the package insert for sitagliptin. A comprehensive literature review revealed six previous reports of rhabdomyolysis due to drug interaction between sitagliptin and statins including simvastatin, lovastatin, and atorvastatin. Of these six cases, only two had developed rhabdomyolysis-associated AKI, none of which were severe enough to require dialysis. As patients are commonly prescribed statins and sitagliptin for treatment of dyslipidemia and diabetes, health care professionals should be aware of this potential drug interaction and closely monitor their patients for signs and symptoms of rhabdomyolysis and AKI. This case highlights the importance of conducting further studies on the risk of muscular toxicity of sitagliptin especially when administered concurrently with statins.

Diabetes pharmacotherapy and effects on the musculoskeletal system

Persons with type 1 or type 2 diabetes have a significantly higher fracture risk than age-matched persons without diabetes, attributed to disease-specific deficits in the microarchitecture and material properties of bone tissue. Therefore, independent effects of diabetes drugs on skeletal integrity are vitally important. Studies of incretin-based therapies have shown divergent effects of different agents on fracture risk, including detrimental, beneficial, and neutral effects. The sulfonylurea class of drugs, owing to its hypoglycemic potential, is thought to amplify the risk of fall-related fractures, particularly in the elderly. Other agents such as the biguanides may, in fact, be osteo-anabolic. In contrast, despite similarly expected anabolic properties of insulin, data suggests that insulin pharmacotherapy itself, particularly in type 2 diabetes, may be a risk factor for fracture, negatively associated with determinants of bone quality and bone strength. Finally, sodium-dependent glucose co-transporter 2 inhibitors have been associated with an increased risk of atypical fractures in select populations, and possibly with an increase in lower extremity amputation with specific SGLT2I drugs. The role of skeletal muscle, as a potential mediator and determinant of bone quality, is also a relevant area of exploration. Currently, data regarding the impact of glucose lowering medications on diabetes-related muscle atrophy is more limited, although preclinical studies suggest that various hypoglycemic agents may have either aggravating (sulfonylureas, glinides) or repairing (thiazolidinediones, biguanides, incretins) effects on skeletal muscle atrophy, thereby influencing bone quality. Hence, the therapeutic efficacy of each hypoglycemic agent must also be evaluated in light of its impact, alone or in combination, on musculoskeletal health, when determining an individualized treatment approach. Moreover, the effect of newer medications (potentially seeking expanded clinical indication into the pediatric age range) on the growing skeleton is largely unknown. Herein, we review the available literature regarding effects of diabetes pharmacotherapy, by drug class and/or by clinical indication, on the musculoskeletal health of persons with diabetes.

Rhabdomyolysis and AKI with Atorvastatin and Sitagliptin Use in the Setting of Low 25-Hydroxyvitamin D Levels

We report a case of an 86-year-old woman admitted to the hospital with rhabdomyolysis and acute kidney injury 3 weeks after starting sitagliptin while on long-term atorvastatin therapy. She also had low levels of 25-hydroxyvitamin D and mild chronic kidney disease, which may have contributed to the development of rhabdomyolysis. A review of the literature reveals four previous reports of this drug interaction in elderly patients, some with underlying kidney disease.

The blood lipid regulation of Monascus-produced monascin and ankaflavin via the suppression of low-density lipoprotein cholesterol assembly and stimulation of apolipoprotein A1 expression in the liver

BACKGROUND/PURPOSES

Monascin (MS) and ankaflavin (AK) produced by Monascus purpureus NTU 568 were proven to show excellent hypolipidemic effects in our previous studies; however, the mechanism is still unclear.

METHODS

This study used MS, AK, and monacolin K as test substances and performed tests on rats fed high-fat and high-cholesterol diet for 8 weeks. The lipid levels and the related protein levels of the rats were assessed to understand the effects of MS, AK, and monacolin K on lipid metabolism.

RESULTS

MS and AK lowered low-density lipoprotein cholesterol (LDL-C) and preserved high-density lipoprotein cholesterol contents. MS and AK inhibited acetyl-coenzyme A acetyltransferase, microsomal triglyceride transfer protein, and apolipoprotein (apo) B-100 expression, thereby preventing LDL assembly. In addition, enhanced LDL-receptor expression increased the transport of LDL-C to the liver for metabolism. MS and AK also significantly increase apo A1 expression, which facilitates high-density lipoprotein cholesterol formation.

CONCLUSION

Monascus-fermented MS and AK can perform blood lipid regulation via the suppression of LDL-C assembly and stimulation of apo A1 expression in liver.

Acute-onset rhabdomyolysis secondary to sitagliptin and atorvastatin interaction

Rhabdomyolysis is a serious medical condition in which the skeletal muscle tissue gets damaged and breaks down at rapid rates, potentially leading to death if not managed early on. Rhabdomyolysis in adults has several etiologies such as crush injuries, prolonged immobilization, strenuous exercise, hormonal or metabolic causes, infections, and drug–drug interactions. We present a case report of the interaction of two drugs that are used commonly in the general population. We here discuss a case of a 60-year-old female who presented to the hospital with complaints of generalized weakness, muscle aches, and atypical chest pain for a week after her primary care physician started her on sitagliptin while she was already on atorvastatin. After review of literature, this is the second known case of such an interaction causing acute breakdown of skeletal musculature.

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.

Association of musculoskeletal complaints and gliptin use: review of spontaneous reports

PURPOSE

Gliptins are new oral antidiabetic drugs that increase insulin levels through dipeptidyl peptidase-4 inhibition. Recently, the association of serious musculoskeletal (MSk) adverse effects with the gliptin use has been suggested. The aim is to describe and analyze the characteristics of spontaneous reports related to these adverse effects and gliptin use.

METHODS

All spontaneous reports with MSk disorders associated with gliptins gathered in the Spanish pharmacovigilance database until May 2012 were described and analyzed using a case/non-case method.

RESULTS

Gliptins were reported as the suspected drug in 332 cases: 208 involved sitagliptin, 115 vildagliptin, and nine saxagliptin. In 34 patients (10.2% of total reports with gliptins), MSk reactions were described (22 women [64.7%] and 12 men [35.3%]). Their mean age was 65.1 years; 41.2% were younger than 65 years. Only seven cases were serious, but the gliptin had to be withdrawn in 22 patients because of intolerance and/or persistence of MSk discomfort, and patients recovered after its discontinuation. A positive re-challenge was observed in two cases. In seven cases, the patients were on previous chronic treatment with statins, and began to present MSk complaints shortly after starting a gliptin. The reporting odds ratio (ROR) for myalgia and arthralgia were strongly associated with gliptin use (ROR 1.96 [95% CI 1.12-3.43], p < 0.05 and ROR 2.69 [95% CI 1.38-5.24], p < 0.05, respectively).

CONCLUSIONS

Musculoskeletal disorders are adverse reactions strongly associated with gliptins that, despite not being serious, may impair the treatment adherence in patients with type 2 diabetes. Future observational studies could confirm these findings.

Effect of ABCB1 polymorphisms and atorvastatin on sitagliptin pharmacokinetics in healthy volunteers

OBJECTIVES

The objectives of this study were to determine if ABCB1 polymorphisms are associated with interindividual variability in sitagliptin pharmacokinetics and if atorvastatin alters the pharmacokinetic disposition of sitagliptin in healthy volunteers.

METHODS

In this open-label, randomized, two-phase crossover study, healthy volunteers were prospectively stratified according to ABCB1 1236/2677/3435 diplotype (n = 9, CGC/CGC; n = 10, CGC/TTT; n = 10, TTT/TTT). In one phase, participants received a single 100 mg dose of sitagliptin; in the other phase, participants received 40 mg of atorvastatin for 5 days, with a single 100 mg dose of sitagliptin administered on day 5. A 24-h pharmacokinetic study followed each sitagliptin dose, and the study phases were separated by a 14-day washout period.

RESULTS

Sitagliptin pharmacokinetic parameters did not differ significantly between ABCB1 CGC/CGC, CGC/TTT, and TTT/TTT diplotype groups during the monotherapy phase. Atorvastatin administration did not significantly affect sitagliptin pharmacokinetics, with geometric mean ratios (90 % confidence intervals) for sitagliptin maximum plasma concentration, plasma concentration-time curve from zero to infinity, renal clearance, and fraction of sitagliptin excreted unchanged in the urine of 0.93 (0.86-1.01), 0.96 (0.91-1.01), 1.02 (0.93-1.12), and 0.98 (0.90-1.06), respectively.

CONCLUSIONS

ABCB1 CGC/CGC, CGC/TTT, and TTT/TTT diplotypes did not influence sitagliptin pharmacokinetics in healthy volunteers. Furthermore, atorvastatin had no effect on the pharmacokinetics of sitagliptin in the setting of ABCB1 CGC/CGC, CGC/TTT, and TTT/TTT diplotypes.

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.

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.

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.

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.