Proteomic analysis in NSAIDs-treated primary cardiomyocytes

NSAIDs (non-steroidal anti-inflammatory drugs) are widely used for the treatment of a variety of inflammatory diseases, but many of them were withdrawn from the market due to their cardiovascular toxicity. In this study, we tried to identify proteins responding to the cellular toxicity in NSAIDs-treated primarily cultured cardiomyocytes using 2-D proteomic analysis. We used seven different NSAIDs (celecoxib, rofecoxib, valdecoxib, diclofenac, naproxen, ibuprofen, and meloxicam) possessing each different degree of cardiovascular risk. Overall protein spots were similar in all NSAIDs-treated cells although numbers of decreased proteins were about 2-fold higher in celecoxib or rofecoxib-treated cells than in cells incubated with other NSAIDs. Many stress-related proteins, cardiac muscle movement proteins and proteins involved in membrane organization have been isolated. Among them, Septin-8, a filament scaffolding protein, showed its specific expression pattern depending on the extent of drug toxicity. Its expression level was low in cells treated by relatively high toxic drugs such as celecoxib, diclofenac, valdecoxib, and rofecoxib. On the contrary, Septin-8 was similarly expressed in control cells in the presence of less toxic drugs such ibuprofen, naproxen, and meloxicam. This data suggests that Septin-8 differentially responds to each NSAID.     

Polyethylene glycol behaves like weak organic solvent

Effect of polyethylene glycol (PEG) on protein solubility has been primarily ascribed to its large hydrodynamic size and thereby molecular crowding effect. However, PEG also shows characteristics of organic solvents. Here, we have examined the solubility of glycine and aliphatic and aromatic amino acids in PEG solutions. PEG400, PEG4000, and PEG20000 decreased the solubility of glycine, though to a much smaller magnitude than the level achieved by typical organic solvents, including ethanol and dimethyl sulfoxide. PEG4000 showed varying degree of interactions with amino acid side chains. The free energy of aliphatic side chains marginally increased by the addition of PEG4000, indicating their weak unfavorable interactions. However, it significantly decreased the free energy of the aromatic side chains and hence stabilized them. Thus, it was concluded that PEG behaves like weak organic solvents; namely PEG destabilized (interacted unfavorably with) polar and charged groups and stabilized (interacted favorably with) aromatic groups. Interestingly, the interaction of PEG20000, but neither PEG400 nor PEG4000, with glycine resulted in phase separation under the saturated concentration of glycine.     

Selective cyclooxygenase-2 inhibitors show a differential ability to inhibit proliferation and induce apoptosis of colon adenocarcinoma cells

Although the influence of selective cyclooxygenase (COX)-2 inhibitors on the proliferation of colon adenocarcinoma cells have been the subject of much investigation, relatively little research has compared the effects of different COX-2 inhibitors. Celecoxib strongly suppressed the proliferation of COX-2 expressing HT-29 cells at 10-40 microM. NS-398 and nimesulide also inhibited cell proliferation, whereas rofecoxib, meloxicam, and etodolac did not. Only celecoxib induced apoptosis of HT-29 cells, as detected on the basis of DNA fragmentation, TUNEL positivity, and caspase-3/7 activation. DNA fragmentation was also increasd in COX-2 non-expressing cell lines (SW-480 and HCT-116) by exposure to celecoxib for 6-24 h. All six COX-2 inhibitors suppressed the production of prostaglandin E(2) by HT-29 cells, suggesting that the pro-apoptotic effect of celecoxib was unrelated to inhibition of COX-2. Inactivation of Akt might explain the differential pro-apoptotic effect of these selective COX-2 inhibitors on colon adenocarcinoma cells.     

Solvatochromic studies in polyethylene glycol–salt aqueous biphasic systems

The polarities of the co-existing phases of a polyethylene glycol (PEG)-2000–K₃PO₄ aqueous biphasic system (ABS) have been examined using Reichardt’s carboxylated pyridinium-N-phenoxybetaine dye as a probe. Using this probe, the polarities of these phases have been compared to those of conventional solvent extraction systems and micellar systems using values obtained from the literature. In general, these extraction systems are comparable in polarity to rather polar solvents. Data on the free energy of transfer of solvents suggests that this may be due to the failure of the probe to account for the real polarity of the salt-rich phase compared to the polymer-rich phase. Examination of the monophasic region of these systems suggests that the reason for this is that the probe is partitioned to a discreet solvent domain dominated by PEG, even though phase separation of the solution is not observed. The use of linear free energy relationships for the characterization of ABS is briefly discussed.     

Polyethylene glycol 400: Solvent and anticonvulsant?

In drug research, administration of agents with limited water solubility frequently requires the use of solvent systems. Such systems are intended to serve as vehicles and ideally, should not possess intrinsic pharmacological activity at useful doses. For over 30 years, the polymeric glycols have enjoyed widespread use because of their unusual solubility characteristics, low order of toxicity and wide range of compatibilities (1). More often than not, their “inertness” has been assumed rather than tested.In the assessment of anticonvulsant efficacy in our monkey model, drugs are administered by continuous intravenous infusion to circumvent the problems of incomplete bioavailability and oscillations in plasma levels. Polyethylene glycol (PEG) has been used at concentrations of 35 to 65% to solubilize carbamazepine, clonazepam and 3-bromo-n-ethylcinnamamide. In all three studies, PEG was also tested alone to control for its potential efficacy. These controls reveal that this solvent possess a defined spectrum of anticonvulsant activity and toxicity.     

Effect of nonsteroidal anti-inflammatory drugs with varying extent of COX-2-COX-1 selectivity on urinary sodium and potassium excretion in the rat

Nonsteroidal anti-inflammatory drugs (NSAIDs) have different selectivity to inhibit cyclooxygenase-1 (COX-1) and COX-2. Treatment with NSAIDs has been associated with kidney side effects. We compared the effect of a selected group of NSAIDs with different COX-2--COX-1 selectivities on urinary sodium and potassium excretion in rats. Each treatment with rofecoxib, celecoxib, meloxicam, diclofenac, and flurbiprofen (30, 120, 9, 30, and 125 mg/kg, respectively) and placebo was administered orally once daily for 4 days. Urine was collected 0-8 h after each dose. Urinary sodium and potassium excretion and urine flow rate were compared with placebo. As compared with placebo, rofecoxib, celecoxib, diclofenac, and flurbiprofen significantly reduced excretion rate of sodium (rofecoxib, 0.28 +/- 0.02 vs. 0.41 +/- 0.03; celecoxib, 0.23 +/- 0.03 vs. 0.48 +/- 0.04; diclofenac, 0.09 +/- 0.02 vs. 0.46 +/- 0.03; and flurbiprofen, 0.11 +/- 0.02 vs. 0.47 +/- 0.02 micromol/(min x 100 g)) and potassium (rofecoxib, 0.55 +/- 0.04 vs. 0.68 +/- 0.04; celecoxib, 0.50 +/- 0.06 vs. 0.72 +/- 0.06; diclofenac, 0.26 +/- 0.05 vs. 0.67 +/- 0.04; and flurbiprofen, 0.35 +/- 0.05 vs. 0.62 +/- 0.03 micromol/ (min x 100 g)). Rofecoxib and flurbiprofen significantly reduced urine flow rate. Meloxicam had no significant effect on either sodium and potassium excretion or on the urine flow rate. At the examined dosage level, no relationship was found between reported COX-2--COX-1 selectivity and urinary electrolytes excretion.     

Pharmacodynamic of cyclooxygenase inhibitors in humans

We provide comprehensive knowledge on the differential regulation of expression and catalysis of cyclooxygenase (COX)-1 and COX-2 in health and disease which represents an essential requirement to read out the clinical consequences of selective and nonselective inhibition of COX-isozymes in humans. Furthermore, we describe the pharmacodynamic and pharmacokinetic characteristics of major traditional nonsteroidal anti-inflammatory drugs (tNSAIDs) and coxibs (selective COX-2 inhibitors) which play a prime role in their efficacy and toxicity. Important information derived from our pharmacological studies has clarified that nonselective COX inhibitors should be considered the tNSAIDs with a balanced inhibitory effect on both COX-isozymes (exemplified by ibuprofen and naproxen). In contrast, the tNSAIDs meloxicam, nimesulide and diclofenac (which are from 18- to 29-fold more potent towards COX-2 in vitro) and coxibs (i.e. celecoxib, valdecoxib, rofecoxib, etoricoxib and lumiracoxib, which are from 30- to 433-fold more potent towards COX-2 in vitro) should be comprised into the cluster of COX-2 inhibitors. However, the dose and frequency of administration together with individual responses will drive the degree of COX-2 inhibition and selectivity achieved in vivo. The results of clinical pharmacology of COX inhibitors support the concept that the inhibition of platelet COX-1 may translate into an increased incidence of serious upper gastrointestinal bleeding but this effect on platelet COX-1 may mitigate the cardiovascular hazard associated with the profound inhibition of COX-2-dependent prostacyclin (PGI2).     

Precipitation of collagens by polyethylene glycols

Types I, II, and III collagens are readily precipitated at neutral pH by polyethylene glycols (PEG). As the molecular weight fraction of the polyethylene glycols increases, they become more effective as precipitants on a weight basis. The amount of PEG required for precipitation depends on the pH, the ionic strength, and the nature of the buffer or salts present. In tissue culture media, low concentrations of collagens and procollagens may be quantitatively precipitated and readily collected by low-speed centrifugation. Polyethylene glycol precipitation can be used to obtain collagens and procollagens from tissue culture media at either analytical or preparative scale, and since the polyethylene glycols do not bind to collagens, the precipitates may be further analyzed directly by chromatographic or electrophoretic methods.     

Preferential hydration and solubility of proteins in aqueous solutions of polyethylene glycol

This paper is focused on the local composition around a protein molecule in aqueous mixtures containing polyethylene glycol (PEG) and the solubility of proteins in water + PEG mixed solvents. Experimental data from literature regarding the preferential binding parameter were used to calculate the excesses (or deficits) of water and PEG in the vicinity of β-lactoglobulin, bovine serum albumin, lysozyme, chymotrypsinogen and ribonuclease A. It was concluded that the protein molecule is preferentially hydrated in all cases (for all proteins and PEGs investigated). The excesses of water and deficits of PEG in the vicinity of a protein molecule could be explained by a steric exclusion mechanism, i.e. the large difference in the sizes of water and PEG molecules.

The solubility of different proteins in water + PEG mixed solvent was expressed in terms of the preferential binding parameter. The slope of the logarithm of protein (lysozyme, β-lactoglobulin and bovine serum albumin) solubility versus the PEG concentration could be predicted on the basis of experimental data regarding the preferential binding parameter. For all the cases considered (various proteins, various PEGs molecular weights and various pHs), our theory predicted that PEG acts as a salting-out agent, conclusion in full agreement with experimental observations. The predicted slopes were compared with experimental values and while in some cases good agreement was found, in other cases the agreement was less satisfactory. Because the established equation is a rigorous thermodynamic one, the disagreement might occur because the experimental results used for the solubility and/or the preferential binding parameter do not correspond to thermodynamic equilibrium.     

Hydrotropic dendrimers of generations 4 and 5: synthesis, characterization, and hydrotropic solubilization of paclitaxel

Polyglycerol dendrimers (PGDs) with 4-5 generations were synthesized and used to investigate the effect of dendritic architecture and its generation on aqueous solubilization of paclitaxel (PTX), a poorly water-soluble drug. Chemical and physical properties of the PGDs were characterized by NMR, MALDI-TOF mass, GPC, viscosity, and dynamic light scattering measurements. The PTX solubility in all the solutions of PGDs, even below 10 wt %, was much higher than that in PEG400 that is commonly used as a cosolvent or a hydrotropic agent. Increase in the PTX solubility by PGDs was dependent on the dendrimer generation. The dendritic structure was the reason for the enhanced solubility of PTX even at low concentrations. (1)H NMR spectra of PTX before and after mixing with PGDs in D(2)O suggested that the aromatic rings and some methyne groups of PTX were surrounded by PGDs. PGDs, which do not require hydrophobic segment as in polymeric micelles, provide an alternative method of hydrotropic solubilization of poorly soluble drugs.     

Effect of solvents on the catalytic activity of firefly luciferase

Various solvents stimulate the catalytic activity of firefly luciferase, up to sevenfold. Polyvinylpyrrolidone, polyethylene glycols, and nonionic detergents such as Triton X-100 were the most effective stimulators of the enzyme. Both peak light and total light emission were enhanced in the presence of these solvents indicating an increased turnover of the enzyme. The primary effect of the solvents is on the oxidative reaction rather than the activation reaction. All the experimental data support the hypothesis that the presence of solvent promotes the dissociation of the inhibitory product from the enzyme.     

The ever-emerging anti-inflammatories. Have there been any real advances?

Gastrointestinal (GI) Adverse Drug Reactions (ADRs) from the NSAIDs are a major cause of morbidity and mortality in arthritic patients taking these drugs. The recent much heralded development of COX-2 selective drugs (celecoxib, rofecoxib), the objective of which has been to spare inhibition of the production of COX-1 derived mucosal protective prostaglandins, may have represented an advance in reducing the risk of serious ADRs--ulcers and bleeding--but does not appear to have reduced the incidence of symptomatic side-effects (nausea, vomiting, epigastric pain/heartburn, abdominal discomfort) which are a major reason for withdrawal from NSAID therapy, especially in the long term. The rationale of COX-2 selectivity from these newer drugs is controversial since there may be pharmacokinetic differences from established carboxylate-NSAIDs that accounts for their apparent lower ulcerogenicity. Moreover, concerns have been recently expressed that as COX-2 is important in ulcer healing, control of prostacyclin production and renal function that they may have adverse reactions from these effects. Indeed, recent reports of enhanced risk of congestive heart failure with rofecoxib are of importance and may relate to impaired prostacyclin production. Moreover, there are other therapeutic strategies that have yielded equally low ulcerogenic NSAIDs (e.g. the prodrug, nabumetone; the established COX-2 inhibitory drug, nimesulide) and even the well-established NSAIDs ibuprofen and diclofenac have relatively low upper GI ulcerogenicity and have been used as benchmark standards in comparative trials of the newer "Oxib" drugs (celecoxib, rofecoxib). Much research interest has centred on the nitric oxide-donating NSAIDs (NO-NSAIDs). The rationale for donating NSAIDs being to counteract the vasoconstriction effects of NSAIDs but this has yet to be fully evaluated. It is not certain that this "antidote" approach will be acceptable as there may also be systemic effects of the nitrobutoxyl--or other NO-donors that may have toxicological consequences. Another strategy is the development of mixed COX-5 lipoxygenase (LOX) inhibitors--the progenitors of which were benoxaprofen and BW-755C. The rationale of reducing the potential for lipoxygenase mediated actions in the stomach (e.g. vasoconstriction, leucocyte accumulation). Clearly, the need to develop newer NSAIDs with lower risks of ulcers and bleeding as well as symptomatic ADRs is still representing a major challenge.     

Monodisperse oligoethylene glycols modified Camptothecin, 10-Hydroxycamptothecin and SN38 prodrugs

Camptothecin, which represents a class of natural products with high anticancer activity, suffers low water solubility which hampers its clinic application. To address this issue, monodisperse polyethylene glycols were employed to modify this class of natural products, including Camptothecin, 10-Hydroxycamptothecin, and SN38. Through selective modification with a series of monodisperse polyethylene glycols, 31 Camptothecin derivatives, including 9 ethers and 22 carbonates, were prepared using a macrocyclic sulfate-based strategy with high efficacy. Monodisperse polyethylene glycols modification provided the Camptothecin derivatives with high purity and fine-tunable water solubility. Through the physicochemical and biological assays, a few novel prodrugs with good solubility, cytotoxicity, and valuable drug release profile were identified as promising anticancer drug candidates.     

Influence of hydrophilic polymers on celecoxib complexation with hydroxypropyl beta-cyclodextrin

Complexation of celecoxib with hydroxypropyl beta-cyclodextrin (HPbetaCD) in the presence and absence of 3 hydrophilic polymers-polyvinyl pyrrolidone (PVP), hydroxypropyl methylcellulose (HPMC), and polyethylene glycol (PEG)-was investigated with an objective of evaluating the effect of hydrophilic polymers on the complexation and solubilizing efficiencies of HPbetaCD and on the dissolution rate of celecoxib from the HPbetaCD complexes. The phase solubility studies indicated the formation of celecoxib-HPbetaCD inclusion complexes at a 1:1M ratio in solution in both the presence and the absence of hydrophilic polymers. The complexes formed were quite stable. Addition of hydrophilic polymers markedly enhanced the complexation and solubilizing efficiencies of HPbetaCD. Solid inclusion complexes of celecoxib-HPbetaCD were prepared in 1:1 and 1:2 ratios by the kneading method, with and without the addition of hydrophilic polymers. The solubility and dissolution rate of celecoxib were significantly improved by complexation with HPbetaCD. The celecoxib-HPbetaCD (1:2) inclusion complex yielded a 36.57-fold increase in the dissolution rate of celecoxib. The addition of hydrophilic polymers also markedly enhanced the dissolution rate of celecoxib from HPbetaCD complexes: a 72.60-, 61.25-, and 39.15-fold increase was observed with PVP, HPMC, and PEG, respectively. Differential scanning calorimetry and X-ray diffractometry indicated stronger drug amorphization and entrapment in HPbetaCD because of the combined action of HPbetaCD and the hydrophilic polymers.     

Acyclovir-Polyethylene Glycol 6000 Binary Dispersions: Mechanistic Insights

The dissolution and subsequent oral bioavailability of acyclovir (ACY) is limited by its poor aqueous solubility. An attempt has been made in this work to provide mechanistic insights into the solubility enhancement and dissolution of ACY by using the water-soluble carrier polyethylene glycol 6000 (PEG6000). Solid dispersions with varying ratios of the drug (ACY) and carrier (PEG6000) were prepared and evaluated by phase solubility, in vitro release studies, kinetic analysis, in situ perfusion, and in vitro permeation studies. Solid state characterization was done by powder X-ray diffraction (XRD), differential scanning calorimetry (DSC), and Fourier transform infrared (FTIR) analysis, and surface morphology was assessed by polarizing microscopic image analysis, scanning electron microscopy, atomic force microscopy, and nuclear magnetic resonance analysis. Thermodynamic parameters indicated the solubilization effect of the carrier. The aqueous solubility and dissolution of ACY was found to be higher in all samples. The findings of XRD, DSC, FTIR and NMR analysis confirmed the formation of solid solution, crystallinity reduction, and the absence of interaction between the drug and carrier. SEM and AFM analysis reports ratified the particle size reduction and change in the surface morphology in samples. The permeation coefficient and amount of ACY diffused were higher in samples in comparison to pure ACY. Stability was found to be higher in dispersions. The results suggest that the study findings provided clear mechanical insights into the solubility and dissolution enhancement of ACY in PEG6000, and such findings could lay the platform for resolving the poor aqueous solubility issues in formulation development.     

Reaction Kinetics of Immobilized α-Chymotrypsin in Organic Media 1. Influence at Solvent Polarity

Esterification of N-acetyl phenylalanine with ethanol catalyzed by immobilized α-chymotrypsin (EC 3.4.21.1) was studied in various reaction media. The effect of reaction medium polarity on enzymatic activity as well as equilibrium yield was measured. The reaction rate increased with increasing amounts of added water, reaching an optimum corresponding to water saturation of the reaction medium. Further additions of water resulted in decreased activity. Bell-shaped activity profiles were obtained for all reaction media tested. Reaction media consisting of pure solvents and of mixtures of solvents were used. The enzymatic activity and the equilibrium yield increased with decreased polarity of the medium. Maximum activity was found in a reaction medium consisting of 80% diisopropyl ether and 20% heptane. The enzymatic activity obtained at optimal water additions in the different solvents and solvents mixtures could be correlated to the solubility of water and the log P of the medium. The equilibrium yield of the reaction was much more closely correlated to the solubility of water than the log P. Much lower enzymatic activity was obtained when solvent mixtures producing water-miscible media were created, than in mixtures producing water-immiscible media, such as mixtures of acetonitrile and diisopropyl ether. The equilibrium yield could be increased by decreasing the water content in the reaction medium, which reduced the water activity.     

Optimization of organic solvent in multiphase biocatalysis

The microbial epoxidation of propene and 1-butene was used to study some fundamental aspects of two-liquid-phase biocatalytic conversions. Introduction of a water-immiscible organic solvent phase in a free-cell suspension gave rise to a series of undesired phenomena, e.g., inactivation by the solvent, clotting of biomass, and aggregation of cells at the liquid-liquid interface. Immobilization of the cells in hydrophilic gels, e.g., calcium alginate, prevented direct cell-organic solvent contact and the related clotting and aggregation of biomass. However, the gel entrapment did not seem to provide additional protection against the organic solvent. The influence of various organic solvents on the retention of immobilized-cell activity was related to solvent properties like the polarity (as expressed by the Hildebrand solubility parameter) and the molecular size (as expressed by the molecular weight or molar volume). High activity retention was favored by a low polarity in combination with a high molecular weight. The solubility parameter also proved useful to describe the capacity of various organic solvents for oxygen and alkene oxides. This facilitated the optimization of the solvent polarity.     

Optimizing lipase activity, enantioselectivity, and stability with medium engineering and immobilization for beta-blocker synthesis.

Lipase from Pseudomonas cepacia showed poor activity and moderate enantioselectivity (E) in pure aqueous systems for hydrolysis of a racemic mixture (+/-)-1-chloro-2-acetoxy-3-(1-naphthyloxy)-propane, which is a potential intermediate for beta-blocker synthesis. However, addition of polar organic solvents to the reaction can change both the activity and the enantioselectivity for this chiral reaction significantly. It was observed, in general, that the activity increases and the enantioselectivity decreases with the increase in the polarity of the organic solvent added to the medium. Among the six solvents chosen (i.e., dimethylsulfoxide [DMSO], 1, 4-dioxane, dimethylformamide [DMF], acetone, 1-propanol, and tetrahydrofuran [THF]), maximum activity and minimum enantioselectivity was obtained with DMSO, whereas minimum activity and maximum enantioselectivity was obtained with THF as the cosolvents. In the subsequent studies, native or polyethylene glycol (PEG)-modified lipase was immobilized by entrapping in Caalginate gel beads. In a fixed-bed continuous reactor containing these catalyst beads, the enzyme was found to be at least three times more enantioselective than the native form in a batch reactor. This fixed-bed reactor with the beads could be operated with high concentration of acetone (33% v/v) for about 1 month without a significant loss of enzyme activity and enantioselectivity.     

Stabilizing effect of organic solvents on oxyhemoglobin

The role of hemoglobin solutions as oxygen carriers in biotechnology are numerous, such as in the oxygen supply to biocatalysts or in the preparation of blood substitutes. However, the major barrier to the successful use of hemoglobin in biological and medical engineering is the autoxidation of heme iron during preparation, storage, and utilization. Fifty-six solvents, chosen among the group of Parker's classification, were studied with regard to the autoxidation kinetics of oxyhemoglobin under nondenaturant conditions. Among these solvents 27 present a concentration range in which the autoxidation rates were reduced compared to autoxidation in water. Three groups of solvent have been observed: one exhibiting only a destabilizing effect regardless of the solvent proportion, a second showing a strong stabilizing effect (k(H2O)/k(solvent) greater than 20) and a third showing a low stabilization (k(H2O)/k(solvent) less than 20). The most effective stabilizing solvents were glycerol, glycols, and alcohols. The effect of hydroorganic solvents could be explained by taking into account the globin solvation by water molecules. The solvents that enhance the structure of the water and form few hydrophobic interactions with globin prevent oxyhemoglobin autoxidation.     

Enhancement of Dissolution Rate of Gliclazide Using Solid Dispersions with Polyethylene Glycol 6000

The aim of the present study was to enhance the dissolution rate of gliclazide using its solid dispersions (SDs) with polyethylene glycol (PEG) 6000. The phase solubility behavior of gliclazide in presence of various concentrations of PEG 6000 in 0.1 N HCl was obtained at 37 °C. The solubility of gliclazide increased with increasing amount of PEG 6000 in water. Gibbs free energy () values were all negative, indicating the spontaneous nature of gliclazide solubilization and they decreased with increase in the PEG 6000 concentration, demonstrating that the reaction conditions became more favorable as the concentration of PEG 6000 increased. The SDs of gliclazide with PEG 6000 were prepared at 1:1, 1:2 and 1:5 (gliclazide/PEG 6000) ratio by melting-solvent method and solvent evaporation method. Evaluation of the properties of the SDs was performed by using dissolution, Fourier-transform infrared (FTIR) spectroscopy, differential scanning calorimetry (DSC) and X-ray diffraction (XRD) studies. The SDs of gliclazide with PEG 6000 exhibited enhanced dissolution rate of gliclazide, and the rate increased with increasing concentration of PEG 6000 in SDs. Mean dissolution time (MDT)of gliclazide decreased significantly after preparation of SDs and physical mixture with PEG 6000. The FTIR spectroscopic studies showed the stability of gliclazide and absence of well-defined gliclazide–PEG 6000 interaction. The DSC and XRD studies indicated the microcrystalline or amorphous state of gliclazide in SDs of gliclazide with PEG 6000.