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

Parallel artificial liquid membrane extraction coupled with UPLC-ESI-MS/MS method for high-throughput quantitation of repaglinide in diabetic patients

A high-throughput therapeutic monitoring method was developed for repaglinide (RPG) in diabetic patients, combining parallel artificial liquid membrane extraction (PALME) with ultraperformance liquid chromatography electrospray ionization tandem mass spectrometry (UPLC-ESI-MS/MS). PALME was performed using a 96-well donor plate comprising a donor solution containing a plasma sample, 50 mM phosphate buffer (pH = 8.0), and cetirizine (CTZ) as internal standard. A polypropylene (PP) porous membrane served as a selective support for the liquid membrane (SLM), preventing nonspecific binding produced by other membranes. The extraction was accomplished across SLM made of PP membrane with dodecyl acetate and 1 % trioctylamine (w/w), and the acceptor solution comprised DMSO and 200 mM formic acid (50:50, v/v). The simple workflow for PALME provided analyte enrichment, highly efficient sample cleanup, high throughput analysis, and excellent reproducibility. Method validation met FDA criteria, with a linear plasma calibration range (0.1-100 ng mL-1, r = 0.9995) and a lower limit of quantitation (LLOQ) of 0.1 ng mL-1. Recovery results at 98.9 % affirmed method reliability. The ability to analyze 198 samples per hour, coupled with a reduced amount of solvents, underscores the method's high throughput and eco-friendly profile. The PALME-UPLC-ESI-MS/MS method was successfully applied to therapeutic drug monitoring of RPG in diabetic patients following 2 mg RPG tablet administration, establishing its effectiveness.

Therapeutic effects of anti-diabetic drugs on traumatic brain injury

AIMS

In this narrative review, we have analyzed and synthesized current studies relating to the effects of anti-diabetic drugs on traumatic brain injury (TBI) complications.

METHODS

Eligible studies were collected from Scopus, Google Scholar, PubMed, and Cochrane Library for clinical, in-vivo, and in-vitro studies published on the impact of anti-diabetic drugs on TBI.

RESULTS

Traumatic brain injury (TBI) is a serious brain disease that is caused by any type of trauma. The pathophysiology of TBI is not yet fully understood, though physical injury and inflammatory events have been implicated in TBI progression. Several signaling pathways are known to play pivotal roles in TBI injuries, including Nuclear factor erythroid 2-related factor 2 (Nrf2), High mobility group box 1 protein/Nuclear factor kappa B (HMGB1/NF-κB), Adiponectin, Mammalian Target of Rapamycin (mTOR), Toll-Like Receptor (TLR), Wnt/β-catenin, Janus Kinase/Signal Transducers and Activators of Transcription (JAK/STAT), Nod-like receptor protein3 (NLRP3) inflammasome, Phosphoglycerate kinase 1/Kelch-like ECH-associated protein 1 (PGK1/KEAP1)/Nrf2, and Mitogen-activated protein kinase (MAPK) . Recent studies suggest that oral anti-diabetic drugs such as biguanides, thiazolidinediones (TZDs), sulfonylureas (SUs), sodium-glucose cotransporter-2 inhibitors (SGLT2is), dipeptidyl peptidase-4 inhibitors (DPPIs), meglitinides, and alpha-glucosidase inhibitors (AGIs) could have beneficial effects in the management of TBI complications. These drugs may downregulate the inflammatory pathways and induce antioxidant signaling pathways, thus alleviating complications of TBI.

CONCLUSION

Based on this comprehensive literature review, antidiabetic medications might be considered in the TBI treatment protocol. However, evidence from clinical trials in patients with TBI is still warranted.

Drug repositioning in thyroid cancer treatment: the intriguing case of anti-diabetic drugs

Cancer represents the main cause of death worldwide. Thyroid cancer (TC) shows an overall good rate of survival, however there is a percentage of patients that do not respond or are refractory to common therapies. Thus new therapeutics strategies are required. In the past decade, drug repositioning become very important in the field of cancer therapy. This approach shows several advantages including the saving of: i) time, ii) costs, iii) de novo studies regarding the safety (just characterized) of a drug. Regarding TC, few studies considered the potential repositioning of drugs. On the other hand, certain anti-diabetic drugs, were the focus of interesting studies on TC therapy, in view of the fact that they exhibited potential anti-tumor effects. Among these anti-diabetic compounds, not all were judjed as appropriate for repositioning, in view of well documented side effects. However, just to give few examples biguanides, DPP-4-inhibitors and Thiazolidinediones were found to exert strong anti-cancer effects in TC. Indeed, their effects spaced from induction of citotoxicity and inhibition of metastatic spread, to induction of de-differentiation of TC cells and modulation of TC microenvironment. Thus, the multifacial anti-cancer effect of these compounds would make the basis also for combinatory strategies. The present review is aimed at discuss data from studies regarding the anti-cancer effects of several anti-diabetic drugs recently showed in TC in view of their potential repositioning. Specific examples of anti-diabetic repositionable drugs for TC treatment will also be provided.

Unlocking the Full Potential of SGLT2 Inhibitors: Expanding Applications beyond Glycemic Control

The number of diabetic patients has risen dramatically in recent decades, owing mostly to the rising incidence of type 2 diabetes mellitus (T2DM). Several oral antidiabetic medications are used for the treatment of T2DM including, α-glucosidases inhibitors, biguanides, sulfonylureas, meglitinides, GLP-1 receptor agonists, PPAR-γ agonists, DDP4 inhibitors, and SGLT2 inhibitors. In this review we focus on the possible effects of SGLT2 inhibitors on different body systems. Beyond the diabetic state, SGLT2 inhibitors have revealed a demonstrable ability to ameliorate cardiac remodeling, enhance myocardial function, and lower heart failure mortality. Additionally, SGLT2 inhibitors can modify adipocytes and their production of cytokines, such as adipokines and adiponectin, which enhances insulin sensitivity and delays diabetes onset. On the other hand, SGLT2 inhibitors have been linked to decreased total hip bone mineral deposition and increased hip bone resorption in T2DM patients. More data are needed to evaluate the role of SGLT2 inhibitors on cancer. Finally, the effects of SGLT2 inhibitors on neuroprotection appear to be both direct and indirect, according to scientific investigations utilizing various experimental models. SGLT2 inhibitors improve vascular tone, elasticity, and contractility by reducing oxidative stress, inflammation, insulin signaling pathways, and endothelial cell proliferation. They also improve brain function, synaptic plasticity, acetylcholinesterase activity, and reduce amyloid plaque formation, as well as regulation of the mTOR pathway in the brain, which reduces brain damage and cognitive decline.

Virtual screening and molecular dynamics simulations provide insight into repurposing drugs against SARS-CoV-2 variants Spike protein/ACE2 interface

After over two years of living with Covid-19 and hundreds of million cases worldwide there is still an unmet need to find proper treatments for the novel coronavirus, due also to the rapid mutation of its genome. In this context, a drug repositioning study has been performed, using in silico tools targeting Delta Spike protein/ACE2 interface. To this aim, it has been virtually screened a library composed by 4388 approved drugs through a deep learning-based QSAR model to identify protein-protein interactions modulators for molecular docking against Spike receptor binding domain (RBD). Binding energies of predicted complexes were calculated by Molecular Mechanics/Generalized Born Surface Area from docking and molecular dynamics simulations. Four out of the top twenty ranking compounds showed stable binding modes on Delta Spike RBD and were evaluated also for their effectiveness against Omicron. Among them an antihistaminic drug, fexofenadine, revealed very low binding energy, stable complex, and interesting interactions with Delta Spike RBD. Several antihistaminic drugs were found to exhibit direct antiviral activity against SARS-CoV-2 in vitro, and their mechanisms of action is still debated. This study not only highlights the potential of our computational methodology for a rapid screening of variant-specific drugs, but also represents a further tool for investigating properties and mechanisms of selected drugs.

Characterization of binding by repaglinide and nateglinide with glycated human serum albumin using high-performance affinity microcolumns

High-performance affinity microcolumns were used to characterize binding by the anti-diabetic drugs repaglinide and nateglinide with normal and glycated forms of human serum albumin. The microcolumns contained only nmol amounts of protein and provided a detailed analysis of these drug interactions with good precision and in a matter of minutes per experiment. The overall binding by repaglinide to normal and glycated albumin fits a model with two types of binding sites: a set of one or two moderate-to-high affinity regions and a larger set of weaker regions with association equilibrium constants of ∼10⁵ and 10³  M^-1 , respectively, at pH 7.4 and 37°C. Competition studies gave site-specific association constants for repaglinide and nateglinide at Sudlow site I of 4.2 × 10⁴ and 5.0 × 10⁴  M^-1 for normal albumin, with a decrease of 26%-30% being seen for nateglinide with glycated albumin and no significant change being noted for repaglinide. At Sudlow site II, repaglinide and nateglinide had association constants for normal albumin of 6.1 × 10⁴ and 7.1 × 10⁵  M^-1 , with glycated albumin giving an increase in the association constant at this site for repaglinide of 1.6- to 1.8-fold and a decrease for nateglinide of 51%-58%.

Comparative efficacy and safety of two insulin aspart formulations (Rapilin and NovoRapid) when combined with metformin, for patients with diabetes mellitus: a multicenter, randomized, open-label, controlled clinical trial

OBJECTIVE

This phase 3 confirmatory diabetes mellitus treatment study compared the safety and efficacy of Rapilin and NovoRapid insulin asparts in combination with metformin.

METHODS

This 24-week, open-label, randomized, active-controlled, noninferiority phase 3 confirmatory study conducted across centers in China aimed to enroll patients with type 2 diabetes mellitus and blood sugar glucose inadequately controlled by oral antidiabetic drugs. Randomized patients received subcutaneous mealtime Rapilin or NovoRapid (3:1) injections, with metformin. The primary objectives were to demonstrate noninferiority (margin of 0.4%) in HbA1c change from baseline and compare safety profiles of Rapilin versus NovoRapid after 24 weeks. Secondary outcomes included 2-h postprandial plasma glucose (PPG), fasting plasma glucose (FPG), and patients achieving HbA1c <7.0% and ≤6.5%.

RESULTS

590 patients with type 2 diabetes mellitus were randomized to Rapilin (n = 441) and NovoRapid (n = 149) groups. After 24 weeks, the mean HbA1c change from baseline was -2.20% (Rapilin) and -2.32% (NovoRapid); the estimated treatment difference based on least-square means was 0.04% (95% CI: -0.17, 0.26), meeting the noninferiority criteria for Rapilin versus NovoRapid. Comparable improvements were reported for mean 2-hour PPG (6.14 and 6.29 mmol/L), FPG (2.02 and 1.70 mmol/L), and patients with HbA1c <7.0% (52.6% and 51.0%) and ≤6.5% (34.2% and 30.9%), in the Rapilin and NovoRapid groups, respectively, with no significant safety or immunogenicity outcome differences.

CONCLUSIONS

Rapilin demonstrated non-inferior glycemic control, and matching safety and immunogenicity to NovoRapid in patients with type 2 diabetes mellitus also receiving metformin over 24 weeks.

TRIAL REGISTRATION

ChiCTR20003129041.

Response surface optimization of a vortex-assisted dispersive liquid-liquid microextraction method for highly sensitive determination of repaglinide in environmental water by HPLC/UV

A vortex-assisted dispersive liquid–liquid microextraction (DLLME) method, mated to chemometrics and combined with HPLC/UV detection was optimized and validated for enrichment and determination of repaglinide in environmental samples using nateglinide as an internal standard (IS). A phosphate buffer (10 mM, pH 2.5): acetonitrile (45:55, v/v) was used as a mobile phase with a flow rate of 1 mL/min in an isocratic elution mode. Chemometrics-assisted optimization was performed using a quadratic integrated d-optimal design. The developed model assessed the statistical significance of the independent variables and their interactions to attain the optimum conditions revealing that extractant type, extractant volume and pH are the most influential factors. Optimization of the extraction procedures was performed with the aid of Design Expert 8® software, which suggested 58 different experiments. The optimal conditions were 30 µL of 1-octanol as extractant, 100 µL of acetonitrile as a disperser at pH 8. Under the optimized conditions, the method showed linearity over the range of 1–100 ng/mL with a limit of detection of 0.4 ng/mL. The accuracy, the intra- and inter-day precision were assessed, the %recoveries were found to be between 98.48 and 100.81% with %RSD lower than 1.3. Using chemometrics in method optimization helped achieve the maximum possible enrichment with the least effort, time, and reagents while considering all possible interactions between variables.

Late-Stage Amination of Drug-Like Benzoic Acids: Access to Anilines and Drug Conjugates through Directed Iridium-Catalyzed C-H Activation

The functionalization of C-H bonds, ubiquitous in drugs and drug-like molecules, represents an important synthetic strategy with the potential to streamline the drug-discovery process. Late-stage aromatic C-N bond-forming reactions are highly desirable, but despite their significance, accessing aminated analogues through direct and selective amination of C-H bonds remains a challenging goal. The method presented herein enables the amination of a wide array of benzoic acids with high selectivity. The robustness of the system is manifested by the large number of functional groups tolerated, which allowed the amination of a diverse array of marketed drugs and drug-like molecules. Furthermore, the introduction of a synthetic handle enabled expeditious access to targeted drug-delivery conjugates, PROTACs, and probes for chemical biology. This rapid access to valuable analogues, combined with operational simplicity and applicability to high-throughput experimentation has the potential to aid and considerably accelerate drug discovery.

Iridium-catalyzed C-H methylation and d 3-methylation of benzoic acids with application to late-stage functionalizations

Late-stage functionalization (LSF) has over the past years emerged as a powerful approach in the drug discovery process. At its best, it allows for rapid access to new analogues from a single drug-like molecule, bypassing the need for de novo synthesis. To be successful, methods able to tolerate the diverse functional groups present in drug-like molecules that perform under mild conditions are required. C-H methylation is of particular interest due to the magic methyl effect in medicinal chemistry. Herein we report an iridium-catalyzed carboxylate-directed ortho C-H methylation and d 3-methylation of benzoic acids. The method uses commercially available reagents and precatalyst and requires no inert atmosphere or exclusion of moisture. Substrates bearing electron-rich and electron-poor groups were successfully methylated, including compounds with competing directing/coordinating groups. The method was also applied to the LSF of several marketed drugs, forming analogues with increased metabolic stability compared with the parent drug.

High-Performance affinity chromatographic studies of repaglinide and nateglinide interactions with normal and glyoxal- or methylglyoxal-modified human albumin serum

During diabetes human serum albumin (HSA), an important drug transport protein, can be modified by agents such as glyoxal (Go) and methylglyoxal (MGo) to form advanced glycation end-products. High-performance affinity microcolumns and zonal elution competition studies were used to compare interactions by the anti-diabetic drugs repaglinide and nateglinide with normal and Go- or MGo-modified HSA at Sudlow sites I and II of this protein. Both drugs had their strongest binding at Sudlow site II for the normal and modified forms of HSA. The association equilibrium constants at this site for repaglinide and nateglinide with normal HSA were 6.1 (± 0.2) × 10⁴ M^-1 and 7.1 (± 0.8) × 10⁵ M^-1, respectively, at pH 7.4 and 37⁰C; these values increased by up to 3.6-fold for repaglinide and decreased by up to 45-55 % for nateglinide when HSA was modified by Go or MGo at levels seen in prediabetes or diabetes. Both drugs were also found to bind at Sudlow site I, with association equilibrium constants at this site on normal HSA of 4.2 (± 0.3) × 10⁴ M^-1 for repaglinide and 5.0 (± 0.1) × 10⁴ M^-1 for nateglinide. The binding strength for repaglinide at Sudlow site I increased by 1.3- to 1.7-fold with the Go-modified HSA and decreased slightly (i.e., up to 19 %) for the MGo-modified HSA, while nateglinide showed only a small or insignificant change in binding with the same modified HSA samples. These results indicated that binding by repaglinide and nateglinide with HSA can be altered significantly by modification of this protein with Go or MGo, making these modifications of potential interest in the treatment of patients with these drugs during diabetes.

Spray dried solid dispersion of repaglinide using hypromellose acetate succinate: in vitro and in vivo characterization

OBJECTIVE

This research study attempted to develop spray-dried solid dispersion, to enhance the solubility of repaglinide, an antidiabetic drug.

SIGNIFICANCE

Aqueous solubility plays a major role in drug delivery because any chemical entity has to be in a dissolved state at the site of absorption, in order to get absorbed. Solid dispersion (SD) is one of the widely used techniques to enhance solubility and hence dissolution rate of poorly soluble drugs.

METHODS

Repagnilide, in hypromellose acetate succinate (HPMCAS) solution, was dried by spray drying to obtain spray-dried solid dispersion (SDSD). Plackett-Burman and Box-Behnken designs were used for screening formulation as well as process parameters, and optimization respectively. DSC, XRD, SEM were carried out to confirm the preparation of solid dispersion. SDSD was evaluated for in vitro dissolution, flow properties, Percentage yield and in vivo oral glucose tolerance test.

RESULT

Spray dried solid dispersion comprising (w/w) drug:polymer ratio of 1:3.82, 2.56% of aerosil and inlet temperature of 90 °C, corresponded to the best formulation obtained in this work. It showed t ₈₅% of less than 15 min and a significant reduction in blood glucose level in rats as compared to pure drug and marketed formulation.

CONCLUSION

Thus, it can be concluded that spray-dried solid dispersion prepared using HPMCAS is a useful technique for solubility and dissolution enhancement of repaglinide.

Mechanisms and Characteristics of Sulfonylureas and Glinides

BACKGROUND

Type 2 diabetes mellitus is a complex progressive endocrine disease characterized by hyperglycemia and life-threatening complications. It is the most common disorder of pancreatic cell function that causes insulin deficiency. Sulfonylurea is a class of oral hypoglycemic drugs. Over the past half century, these drugs, together with the subsequent non-sulfonylureas (glinides), have been the main oral drugs for insulin secretion.

OBJECTIVE

Through in-depth study, the medical profession considers it as an important drug for improving blood sugar control.

METHODS

The mechanism, characteristics, efficacy and side effects of sulfonylureas and glinides were reviewed in detail.

RESULTS

Sulfonylureas and glinides not only stimulated the release of insulin from pancreatic cells, but also had many extrapanular hypoglycemic effect, such as reducing the clearance rate of insulin in liver, reducing the secretion of glucagon, and enhancing the sensitivity of peripheral tissues to insulin in type 2 diabetes mellitus.

CONCLUSION

Sulfonylureas and glinides are effective first-line drugs for the treatment of diabetes mellitus. Although they have the risk of hypoglycemia, weight gain and cardiovascular disease, their clinical practicability and safety can be guaranteed as long as they are reasonably used.

A novel drug–drug coamorphous system without molecular interactions: improve the physicochemical properties of tadalafil and repaglinide

Tadalafil and repaglinide, categorized as BCS class II drugs, have low oral bioavailabilities due to their poorly aqueous solubilities and dissolutions. The aim of this study was to enhance the dissolution of tadalafil and repaglinide by co-amorphization technology and evaluate the storage and compression stability of such coamorphous system. Based on Flory–Huggins interaction parameter (χ ≤ 0) and Hansen solubility parameter (δ_t ≤ 7 MPa^0.5) calculations, tadalafil and repaglinide was predicted to be well miscible with each other. Coamorphous tadalafil–repaglinide (molar ratio, 1 : 1) was prepared by solvent-evaporation method and characterized with respect to its thermal properties, possible molecular interactions. A single T_g (73.1 °C) observed in DSC and disappearance of crystallinity in PXRD indicated the formation of coamorphous system. Principal component analysis of FTIR in combination with Raman spectroscopy and Ss ¹³C NMR suggested the absence of intermolecular interactions in coamorphous tadalafil–repaglinide. In comparison to pure crystalline forms and their physical mixtures, both drugs in coamorphous system exhibited significant increases in intrinsic dissolution rate (1.5–3-fold) and could maintain supersaturated level for at least 4 hours in non-sink dissolution. In addition, the coamorphous tadalafil–repaglinide showed improved stability compared to the pure amorphous forms under long-term stability and accelerated storage conditions as well as under high compressing pressure. In conclusion, this study showed that co-amorphization technique is a promising approach for improving the dissolution rate of poorly water-soluble drugs and for stabilizing amorphous drugs.

The coamorphous tadalafil–repaglinide (molar ratio, 1 : 1) prepared by solvent-evaporation method significantly improve the physicochemical properties of tadalafil and repaglinide.

Repaglinide-loaded nanostructured lipid carriers with different particle sizes for improving oral absorption: preparation, characterization, pharmacokinetics, and in situ intestinal perfusion

Repaglinide-loaded nanostructured lipid carriers (REP-NLCs) with different particle sizes were successfully designed and prepared to investigate the permeation and absorption ability by in situ single-pass intestinal perfusion (SPIP) study and pharmacokinetics. Both of the formulations prepared by solvent diffusion method exhibited a spherical shape under transmission electron microscopy (TEM) and similar zeta potential value of –11 mV. The particles size, encapsulation efficiency (EE), drug loading (DL) of REP-NLCs-Small and REP-NLCs-Large size preparations were about 79 nm and 325 nm, 96.83% and 98.60%, 4.41% and 3.05%, respectively. Besides, both REP-NLCs showed good colloidal stability and had no burst release phenomenon compared with REP-Sol. SPIP demonstrated the improved membrane permeability for NLCs compared with REP-Sol, especially NLCs-Small size preparation. The bioavailability increased sequentially in REP-Sol, REP-NLCs-Large, and REP-NLCs-Small, and the difference between each other was statistical significant. Our investigations demonstrate that NLCs with small particles size of 50–100 nm, such as 79 nm, are able to enhance absorption performance of a poorly soluble repaglinide compared with large particles size, such as 325 nm, by significantly improving the absorption in jejunum, and colon of rats and thus well improving oral bioavailability.

Short-term efficacy and safety of repaglinide versus glimepiride as augmentation of metformin in treating patients with type 2 diabetes mellitus

Background: Consistent evidence is still lacking on which one, glimepiride plus metformin or repaglinide plus metformin, is better in treating type 2 diabetes mellitus (T2DM). Therefore, this study was conducted to compare the short-term efficacy and safety of these two methods in treating T2DM. Methods: The literature research dating up to August 2018 was conducted in the electronic databases. The randomized controlled trials (RCTs) comparing the short-term (treatment period ≤12 weeks) efficacy and safety of these two methods in treating patients with T2DM were included. No language limitation was used in this study. The decreased hemoglobin A1c (HbA1c), fasting plasma glucose (FPG), and 2h plasma glucose (2hPG) levels were used as the primary outcome to assess the efficacy, and the adverse events and hypoglycemia were used as the secondary outcome to assess the safety. Results: In total, 11 RCTs composed of 844 T2DM patients were included. The results showed that there were no significant differences in decreasing HbA1c and FPG levels between the two methods, but the estimated standardized mean differences favored the repaglinide plus metformin. Meanwhile, the repaglinide plus metformin was significantly more effective in decreasing 2hPG levels than glimepiride plus metformin. In addition, fewer patients reported adverse events and experienced hypoglycemia in the repaglinide plus metformin group. Conclusion: These results indicated that the repaglinide plus metformin might have some advantages over glimepiride plus metformin in the short-term treatment of patients with T2DM, and should be further explored.

Study Design Selection in Early Clinical Anti-Hyperglycemic Drug Development: A Simulation Study of Glucose Tolerance Tests

In antidiabetic drug development, phase I studies usually involve short‐term glucose provocations. Multiple designs are available for these provocations (e.g., meal tolerance tests (MTTs) and graded glucose infusions (GGIs)). With a highly nonlinear, complex system as the glucose homeostasis, the various provocations will contribute with different information offering a rich choice. Here, we investigate the most appropriate study design in phase I for several hypothetical mechanisms of action of a study drug. Five drug effects in diabetes therapeutic areas were investigated using six study designs. Power to detect drug effect was assessed using the likelihood ratio test, whereas precision and accuracy of the quantification of drug effect was assessed using stochastic simulation and estimations. An overall summary was developed to aid designing the studies of antihyperglycemic drug development using model‐based analysis. This guidance is to be used when the integrated glucose insulin model is used, involving the investigated drug mechanisms of action.

Development of repaglinide microspheres using novel acetylated starches of bitter and Chinese yams as polymers

Tropical starches from Dioscorea dumetorum (bitter) and Dioscorea oppositifolia (Chinese) yams were acetylated with acetic anhydride in pyridine medium and utilized as polymers for the delivery of repaglinide in microsphere formulations in comparison to ethyl cellulose. Acetylated starches of bitter and Chinese yams with degrees of substitution of 2.56 and 2.70 respectively were obtained. Acetylation was confirmed by FTIR, ¹H NMR spectroscopy. A 3² factorial experimental design was performed using polymer type and drug-polymer ratio as independent variables. Particle size, swelling, entrapment and time for 50% drug release (t₅₀) were dependent variables. Contour plots showed the relationship between the independent factors and the response variables. All variables except swelling increased with drug: polymer ratio. Entrapment efficiency was generally in the rank of Bitter yam>Ethyl cellulose>Chinese yam. Repaglinide microspheres had size 50±4.00 to 350±18.10μm, entrapment efficiency 75.30±3.03 to 93.10±2.75% and t₅₀ 3.20±0.42 to 7.20±0.55h. Bitter yam starch gave longer dissolution times than Chinese yam starch at all drug-polymer ratios. Drug release fitted Korsmeyer-Peppas and Hopfenberg models. Acetylated bitter and Chinese yam starches were found suitable as polymers to prolong release of repaglinide in microsphere formulations.

Altered pharmacokinetics and pharmacodynamics of repaglinide by ritonavir in rats with healthy, diabetic and impaired hepatic function

BACKGROUND

Ritonavir is an antiretroviral drug to treat HIV AIDS and inhibits cytochrome P450 3A4. To treat diabetes mellitus in HIV, repaglinide is coadministered with ritonavir in the clinic. Multiple cytochrome P450 (CYP) isoforms are involved in the metabolism of repaglinide like CYP2C8 and CYP 3A4. In order to predict and understand drug-drug interactions of these two drugs, the pharmacokinetics and pharmacodynamics (PK/PD) of repaglinide and ritonavir were studied in normal, diabetic and hepatic impaired rats. The purpose of the study was to assess the influence of ritonavir on the PK/PD of repaglinide in rats with normal, diabetic and impaired hepatic function.

METHODS

Human oral therapeutic doses of ritonavir and repaglinide were extrapolated to rats based on the body surface area. Ritonavir (20 mg/kg, p.o.), alone and along with repaglinide (0.5 mg/kg, p.o.), was given to normal, diabetic and hepatic impaired rats, and the PK/PD were studied.

RESULTS

The pharmacokinetic parameters like peak plasma concentration (Cmax), area under the plasma concentration time profile (AUC) and elimination half life of repaglinide were significantly (p<0.0001) increased when compared to repaglinide control rats. The repaglinide clearance (CL) was significantly (p<0.0001) decreased in the presence of ritonavir treatment. In the presence of ritonavir, repaglinide hypoglycemic activity was increased significantly (p<0.0005) when compared with repaglinide control group.

CONCLUSIONS

The significant difference in the PK/PD changes have been due to the increased plasma exposure and decreased total body clearance of repaglinide, which may be due to the inhibition of the CYP P450 metabolic system and organic anion-transporting polypeptide transporter by ritonavir.

Charge-assisted intermolecular hydrogen bond formed in coamorphous system is important to relieve the pH-dependent solubility behavior of lurasidone hydrochloride

In comparison to amorphous LH, coamorphous LH-REP without evidence of intermolecular hydrogen bond, exhibited greatly improved solubility with pH-dependent behavior, significantly enhanced dissolution rate and physical stability.

Repaglinide-loaded solid lipid nanoparticles: effect of using different surfactants/stabilizers on physicochemical properties of nanoparticles

BACKGROUND

Repaglinide is an efficient anti-diabetic drug which is prescribed widely as multi-dosage oral daily regimens. Due to the low compliance inherent to each multi-dosage regimen, development of prolonged-release formulations could enhance the overall drug efficacy in patient populations.

METHODS

Repaglinide-loaded solid lipid nanoparticles (SLNs) were developed and characterized in vitro. Various surfactants were used in this study during the nanocarrier preparation procedure and their corresponding effects on some physicochemical properties of SLNs such as size, zeta potential; drug loading parameters and drug release profiles was investigated. Stearic acid and glyceryl mono stearate (GMS) were used as lipid phase and phosphatidylcholin, Tween80, Pluronic F127, poly vinyl alcohol (PVA) and polyvinyl pyrrolidone (PVP) were used as surfactant/stabilizer.

RESULTS

The results showed some variations between formulations; where the Tween80-based SLNs showed smallest size, the phosphatidylcholin-based SLNs indicated most prolonged drug release time and the highest loading capacity. SEM images of these formulations showed morphological variations and also confirmed the nanoscale size of these particles. The FTIR and DSC results demonstrated no interaction between drug and excipients. The invitro release profiles of different formulations were studied and observed slow release of drug from all formulations. However significant differences were found among them in terms of their initial burst release as well as the whole drug release profile. From fitting these data to various statistical models, the Peppas model was proposed as the best model to describe the statistical indices and, therefore, mechanism of drug release.

CONCLUSION

The results of this study confirmed the effect of surfactant type on SLNs physicochemical properties such as morphological features, loading parameters, particle sizes and drug release kinetic. With respect to the outcome data, the mixture of phosphatidylcholin/Pluronic F127 was selected as the best surfactant/stabilizer to coat the lipid core comprising stearic acid and GMS.

Alternative Medicine in Diabetes - Role of Angiogenesis, Oxidative Stress, and Chronic Inflammation

Diabetes is a chronic metabolic disorder that is characterized by hyperglycemia due to lack of or resistance to insulin. Patients with diabetes are frequently afflicted with ischemic vascular disease and impaired wound healing. Type 2 diabetes is known to accelerate atherosclerotic processes, endothelial cell dysfunction, glycosylation of extracellular matrix proteins, and vascular denervation. Herbal medicines and naturally occurring substances may positively affect diabetes management, and could thus be utilized as cost-effective means of supporting treatment in developing countries. Natural treatments have been used in these countries for a long time to treat diabetes. The present review analyses the features of aberrant angiogenesis, abnormalities in growth factors, oxidative stress, and metabolic derangements relevant to diabetes, and how herbal substances and their active chemical constituents may counteract these events. Evidence for possible biochemical effectiveness and limitations of herbal medicines are given, as well as details regarding the role of cytokines and nitric oxide.

Pharmacogenomics of glinides

Glinides, including repaglinide, nateglinide and mitiglinide, are a type of fasting insulin secretagogue that could help to mimic early-phase insulin release, thus providing improved control of the postprandial glucose levels. Glinides stimulate insulin secretion by inhibiting ATP-sensitive potassium channels in the pancreatic β-cell membrane. Although glinides have been widely used clinically and display excellent safety and efficacy, the response to glinides varies among individuals, which is partially due to genetic factors involved in drug absorption, distribution, metabolism and targeting. Several pharmacogenomic studies have demonstrated that variants of genes involved in the pharmacokinetics or pharmacodynamics of glinides are associated with the drug response. Polymorphisms of genes involved in drug metabolism, such as CYP2C9, CYP2C8 and SLCO1B1, may influence the efficacy of glinides and the incidence of adverse effects. In addition, Type 2 diabetes mellitus susceptibility genes, such as KCNQ1, PAX4 and BETA2, also influence the efficacy of glinides. In this article, we review and discuss current pharmacogenomics researches on glinides, and hopefully provide useful data and proof for clinical application.

Effects of nifedipine on the pharmacokinetics of repaglinide in rats: possible role of CYP3A4 and P-glycoprotein inhibition by nifedipine

BACKGROUND

The aim of this study was to investigate the effects of nifedipine on the bioavailability and pharmacokinetics of repaglinide in rats.

METHODS

The effect of nifedipine on P-glycoprotein (P-gp) and cytochrome P450 (CYP) 3A4 activity was evaluated. The pharmacokinetic parameters of repaglinide and blood glucose concentrations were also determined in rats after oral (0.5 mg/kg) and intravenous (0.2 mg/kg) administration of repaglinide to rats in the presence and absence of nifedipine (1 and 3 mg/kg).

RESULTS

Administration of nifedipine resulted in inhibition CYP3A4 activity with an IC50 value of 7.8 μM, and nifedipine significantly inhibited P-gp activity in a concentration-dependent manner. Compared to the oral control group, nifedipine significantly increased the area under the plasma concentration-time curve (AUC0-∞) and the peak plasma concentration (Cmax) of repaglinide by 49.3 and 25.5%, respectively. Nifedipine significantly decreased the total body clearance (CL/F) of repaglinide by 22.0% compared to the oral control group. Nifedipine also increased the absolute bioavailability (AB) of repaglinide by 50.0% compared to the oral control group (33.6%). In addition, the relative bioavailability (RB) of repaglinide was 1.16- to 1.49-fold greater than that of the control group. Compared to the intravenous control, nifedipine significantly increased AUC0-∞ of repaglinide. Blood glucose concentrations had significant differences compared to the oral control groups.

CONCLUSION

Nifedipine enhanced the oral bioavailability of repaglinide, which may be mainly attributable to inhibition of CYP3A4-mediated metabolism of repaglinide in the small intestine and/or in the liver and to inhibition of the P-gp efflux transporter in the small intestine and/or reduction of total body clearance by nifedipine. The current study has raised awareness of potential drug interactions by concomitant use of repaglinide with nifedipine.

Meglitinide analogues in adolescent patients with HNF1A-MODY (MODY 3)

For pediatric patients with hepatocyte nuclear factor-1A (HNF1A)-maturity-onset diabetes of the young (MODY 3), treatment with sulfonylureas is recommended. In adults with HNF1A-MODY, meglitinide analogues achieve lower postprandial glucose levels and pose a lower risk of delayed hypoglycemia compared with sulfonylureas. This therapy has not yet been reviewed in pediatric patients. We report on meglitinide analogue treatment in 3 adolescents with HNF1A-MODY. Case 1 (14-year-old girl) was diagnosed asymptomatically but had an hemoglobin A1c (HbA1c) level of 7.4%; her father had been recently diagnosed with HNF1A-MODY. With repaglinide, her HbA1c level decreased to 5.5%, with no hypoglycemic episodes. Case 2 (14-year-old boy) was diagnosed incidentally with glucosuria (HbA1c level: 7.0%) and was treated with insulin. After the HNF1A-MODY diagnosis, he was switched to glibenclamide. Due to several hypoglycemic episodes, treatment was changed to nateglinide and his HbA1c level decreased to 6.2% with no further hypoglycemic episodes. Case 3 (11-year-old girl) presented with polyuria and polydipsia (HbA1c level: 10.1%) and was initially treated with insulin. After the HNF1A-MODY diagnosis, treatment was changed to repaglinide. She was obese (BMI: 28.8 kg/m(2); z-score: +2.2), and glucose control with repaglinide alone was insufficient. Therefore, neutral protamine Hagedorn insulin (0.27 U/kg per day) was added. With this combination therapy, her HbA1c level decreased to 8.2%. The use of meglitinides in these 3 adolescent patients was well tolerated and effective. Furthermore, hypoglycemic episodes were rare compared with treatment with insulin or sulfonylureas. We therefore suggest considering meglitinides as the primary oral treatment option for adolescents suffering from HNF1A-MODY.

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

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

Design and evaluation of self-nanoemulsifying pellets of repaglinide

The aim of study was to develop self-nanoemulsifying pellets (SNEP) for oral delivery of poorly water soluble drug, repaglinide (RPG). Solubility of RPG in oily phases and surfactants was determined to identify components of self-nanoemulsifying drug delivery system (SNEDDS). The surfactants and cosurfactants were screened for their ability to emulsify oily phase. Ternary phase diagrams were constructed to identify nanoemulsification area for the selected systems. SNEDDS formulations with globule size less than 100 nm were evaluated for in vivo anti-hyperglycemic activity in neonatal streptozotocin rat model. A significant reduction in glucose levels was produced by optimized SNEDDS formulation in comparison to the control group. The optimized SNEDDS formulations were pelletized via extrusion/spheronization technique using microcrystalline cellulose and lactose. SNEP were characterized by X-ray powder diffraction and scanning electron microscopy. X-ray diffraction study indicated loss of crystallinity of RPG in SNEP. The SNEP exhibited good flow properties, mechanical strength and formed nanoemulsion with globule size less than 200 nm. SNEP showed in vitro release of more than 80% RPG in 10 min which was significantly higher than RPG containing reference pellets. In conclusion, our studies illustrated that RPG, a poorly water soluble drug can be successfully formulated into SNEP which can serve as a promising system for the delivery of poorly water soluble drugs.

Effects of Fluvastatin on the Pharmacokinetics of Repaglinide: Possible Role of CYP3A4 and P-glycoprotein Inhibition by Fluvastatin

The purpose of this study was to investigate the effects of fluvastatin on the pharmacokinetics of repaglinide in rats. The effect of fluvastatin on P-glycoprotein and CYP3A4 activity was evaluated. The pharmacokinetic parameters and blood glucose concentrations were also determined after oral and intravenous administration of repaglinide to rats in the presence and absence of fluvastatin. Fluvastatin inhibited CYP3A4 activity in a concentration-dependent manner with a 50% inhibition concentration(IC₅₀) of 4.1 µM and P-gp activity. Compared to the oral control group, fluvastatin significantly increased the AUC and the peak plasma level of repaglinide by 45.9% and 22.7%, respectively. Fluvastatin significantly decreased the total body clearance (TBC) of repaglinide compared to the control. Fluvastatin also significantly increased the absolute bioavailability (BA) of repaglinide by 46.1% compared to the control group. Moreover, the relative BA of repaglinide was 1.14- to 1.46-fold greater than that of the control. Compared to the i.v. control, fluvastatin significantly increased the AUC_0-∞ of i.v. administered repaglinide. The blood glucose concentrations showed significant differences compared to the oral controls. Fluvastatin enhanced the oral BA of repaglinide, which may be mainly attributable to the inhibition of the CYP3A4-mediated metabolism of repaglinide in the small intestine and/or liver, to the inhibition of the P-gp efflux transporter in the small intestine and/or to the reduction of TBC of repaglinide by fluvastatin. The study has raised the awareness of potential interactions during concomitant use of repaglinide with fluvastatin. Therefore, the concurrent use of repaglinide and fluvastatin may require close monitoring for potential drug interactions.

Ficus deltoidea: A Potential Alternative Medicine for Diabetes Mellitus

Ficus deltoidea from the Moraceae family has been scientifically proven to reduce hyperglycemia at different prandial states. In this study, we evaluate the mechanisms that underlie antihyperglycemic action of Ficus deltoidea. The results had shown that hot aqueous extract of Ficus deltoidea stimulated insulin secretion significantly with the highest magnitude of stimulation was 7.31-fold (P < 0.001). The insulin secretory actions of the hot aqueous extract involved K⁺  _ATP channel-dependent and K⁺  _ATP-channel-independent pathway. The extract also has the ability to induce the usage of intracellular Ca²⁺ to trigger insulin release. The ethanolic and methanolic extracts enhanced basal and insulin-mediated glucose uptake into adipocytes cells. The extracts possess either insulin-mimetic or insulin-sensitizing property or combination of both properties during enhancing glucose uptake into such cells. Meanwhile, the hot aqueous and methanolic extracts augmented basal and insulin-stimulated adiponectin secretion from adipocytes cells. From this study, it is suggested that Ficus deltoidea has the potential to be developed as future oral antidiabetic agent.

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

Oral repaglinide (GlucoNorm®; NovoNorm®; Prandin®; Surepost®) is a rapid-acting insulin secretagogue that lowers postprandial glucose (PPG) excursions by targeting early-phase insulin release, with reductions in PPG considered to be important in reducing long-term cardiovascular complications of diabetes mellitus. Repaglinide, a carbamoylbenzoic acid derivative, is chemically related to the meglitinide class of insulin secretagogues, but unrelated to the sulfonylurea insulin secretagogues. Meglitinides, including repaglinide, have a distinct binding site at the β-cell membrane, which differs from that of sulfonylureas, and corresponds to greater insulinotropic effects with repaglinide than with glibenclamide and/or glimepiride and a more rapid onset of action in in vitro and in vivo studies. This article reviews the clinical efficacy and tolerability of oral repaglinide in the treatment of patients with type 2 diabetes and provides an overview of its pharmacological properties. In well designed clinical trials of up to 52 weeks' duration and in the clinical practice setting, recommended dosages of repaglinide (0.5-4 mg three times daily up to 30 minutes prior to a meal) provided effective glycaemic control and were generally well tolerated in treatment-naive or -experienced adult patients with type 2 diabetes, including elderly patients and those with renal impairment. Furthermore, as monotherapy or in combination with other oral antihyperglycaemic drugs, repaglinide was at least as effective as other oral antihyperglycaemic drugs at improving or maintaining glycaemic control, with a tolerability profile that was generally similar to that of sulfonylurea drugs and nateglinide. Thus, repaglinide remains an effective option for the management of patients with type 2 diabetes.

Effects of efonidipine on the pharmacokinetics and pharmacodynamics of repaglinide: possible role of CYP3A4 and P-glycoprotein inhibition by efonidipine

The purpose of this study was to investigate the effects of efonidipine on the pharmacokinetics and pharmacodynamics of repaglinide in rats. The pharmacokinetic parameters of repaglinide and blood glucose concentrations were also determined in rats after oral (0.5 mg/kg) and intravenous (0.2 mg/kg) administration of repaglinide to rats in the presence and absence of efonidipine (1 and 3 mg/kg). Efonidipine inhibited CYP3A4 activity with an IC(50) value of 0.08 μM, and efonidipine significantly inhibited P-gp activity in a concentration-dependent manner. Compared to the oral control group, efonidipine significantly increased the area under the plasma concentration-time curve (AUC(0-∞)) (P < 0.01 for 3 mg/kg) and the peak plasma concentration (C (max)) (P < 0.05 for 3 mg/kg) of repaglinide by 51.3 and 28.6%, respectively. Efonidipine also significantly (P < 0.01 for 3 mg/kg) increased the absolute bioavailability (AB) of repaglinide by 51.5% compared to the oral control group (33.6%). Moreover, efonidipine significantly increased (P < 0.05 for 3 mg/kg) the AUC(0-∞) of intravenously administered repaglinide. Consistent with these kinetic alterations, the hypoglycemic effect in the concurrent administration group was more pronounced than that in the control group (i.e., repaglinide alone) when the drug was given orally. A pharmacokinetic/dynamic model involving 2-compartment open model with inhibition in absorption/elimination and an indirect response model was apparently sufficient in estimating the concentration-time and effect-time profiles of repaglinide with or without efonidipine. Present study has raised the awareness of potential drug interactions by concomitant use of efonidipine with repaglinide, since efonidipine may alter the absorption and/or elimination of repaglinide by the inhibition of CYP3A4 and P-gp efflux pump. Therefore, the concurrent use of efonidipine with repaglinide may require a close monitoring for potential drug interactions.

The molecular genetics of sulfonylurea receptors in the pathogenesis and treatment of insulin secretory disorders and type 2 diabetes

Sulfonylurea receptors (SURs) form an integral part of the ATP-sensitive potassium (K(ATP)) channel complex that is present in most excitable cell types. K(ATP) channels couple cellular metabolism to electrical activity and provide a wide range of cellular functions including stimulus secretion coupling in pancreatic β cells. K(ATP) channels are composed of SURs and inward rectifier potassium channel (Kir6.x) subunits encoded by the ABCC8/9 and KCNJ8/11 genes, respectively. Recent advances in the genetics, molecular biology, and pharmacology of SURs have led to an increased understanding of these channels in the etiology and treatment of rare genetic insulin secretory disorders. Furthermore, common genetic variants in these genes are associated with an increased risk for type 2 diabetes. In this review we summarize the molecular biology, pharmacology, and physiology of SURs and K(ATP) channels, highlighting recent advances in their genetics and understanding of rare insulin secretory disorders and susceptibility to type 2 diabetes.