Update on compatibility assessment of empagliflozin with the selected pharmaceutical excipients employed in solid dosage forms by thermal, spectroscopic and chromatographic techniques.

Empagliflozin (EGF) received USFDA approval in 2014 for oral use to control the glucose levels in adults with type 2 diabetes mellitus. Albeit, a systematic drug-excipient compatibility study of EGF has not been reported in the open literature. As physical and chemical interactions affect the performance of the formulation, this study intended to unveil the drug and excipients interactions which would later help in development of a robust solid dosage form. Differential scanning calorimetry (DSC) was applied as a screening tool for the assessment of compatibility between EGF and the list of excipients mentioned in the EMEA summary of product characteristics (SmPC)-section 6.1, along with mannitol and polyvinylpyrrolidone. Thermogravimetric analysis (TGA), Fourier Transform Infrared Spectroscopy (FTIR), X-ray Powder Diffraction (PXRD) and Hot Stage Microscopy (HSM) methods were utilized to appraise the interpretation of DSC results adequately. Isothermal stress testing (IST) studies of EGF were performed using the selected excipients to check the presence of interaction products (IPs) and the drug content by HPLC. Additional peaks were observed in the EGF-macrogol mixture than the drug peak in the HPLC analysis after two and half months, and those were separated and identified by the Ultra-High Performance Liquid Chromatography-Quadrupole Time of Flight Mass Spectrometry (UHPLC-QTOF-MS). Overall, EGF had shown compatibility with 13 selected excipients; however, initial observation of DSC and IST studies indicated plausible interaction of the EGF with macrogol.

On the assessment of the stability of vitrified cryo-media by differential scanning calorimetry: A new tool for biobanks to derive standard operating procedures for storage, access and transport.

When a vitrified sample is heated over the glass transition temperature it may start to devitrify endangering the sample. The ability to estimate the stability of the vitrified state can help in the development of new vitrification media as well as handling procedures. By employing differential scanning calorimetry, we can measure the ice crystallization rate in a vitrified sample and thus study the devitrification kinetics. Using this technique, we have studied samples comprised of PBS with cryoprotective additives (CPA) as dimethylsulfoxide (Me2SO), ethylene glycol (EG) and mixtures thereof, regarding the dependence of the devitrification kinetics on the CPA concentration. We found that already small concentration changes lead to significant changes in the devitrification times. Changing the CPA concentration by 4 wt% changed the devitrification time with a factor of 342 and 271 for Me2SO and EG, respectively. Concentration changes in EG/Me2SO mixtures was found to have a smaller impact on the devitrification kinetics compared to the pure CPA samples. Our data suggest that these significant increases in the devitrification times are primarily due to a relation between nucleation rates and the CPA concentration. Finally, we investigated an established vitrification medium used to preserve human embryonic stem cells. This medium was found to have the poorest glass stability in this study and reflects the tradeoff between stability and biocompatibility. The present work finally provides a tool to evaluate handling and storage procedures when employing vitrification as a cryopreservation method and underlines the importance of these.

Preparation, characterization and ex vivo-in vivo assessment of candesartan cilexetil nanocrystals via solid dispersion technique using an alkaline esterase activator carrier.

The objective of this study was to improve candesartan cilexetil (CC) efficacy by formulating nanocrystals via solid dispersion (SD) technique using tromethamine (Tris). SD was prepared by solvent evaporation at different drug carrier ratios, evaluated for particle size, vitro dissolution studies, TEM, FTIR, and X-ray powder diffraction. Ex vivo, in vivo pharmacokinetic parameters were conducted on selected formulae compared to drug suspension and marketed product. Size analysis demonstrated formation of particles in the nanorange lower than 300 nm. A burst drug release followed by an improved dissolution was observed indicating instant formation of nanocrystals along with amorphization as confirmed by X-ray diffraction. FTIR studies suggested the absence of chemical interaction between Tris and CC. TEM revealed formation of irregular oval nanoparticles. SD-1:5 has higher apparent permeability coefficient compared to CC suspension. Furthermore, the pharmacokinetic results proved the ability of the formed nanoparticles to enhance the efficacy of CC compared to drug suspension and marketed product. In conclusion, using of Tris as alkaline esterase activator carrier could be a promising tool to bypass the controversial effect of esterase enzymes that may be a source for inter-individual variations affecting ester prodrug candidates' efficacy.

Antioxidant activity and photostability assessment of trans-resveratrol acrylate microspheres.

Trans-resveratrol (RSV) was microencapsulated in Eudragit® RS100 and RL100 resin blends. Lyophilized microspheres were characterized in the solid state for their micromeritic properties and drug loading. FT-IR, PXRD, and DSC analyzes suggested that RSV formed an intimate microcrystalline dispersion within the polymer network, also confirmed by SEM analysis. This produced a reduced degradation of RSV after storage at 40 °C, compared to the neat drug, and a protection of the drug from UV light-induced trans-cis isomerization (60% intact drug was found after 60 s irradiation at 350 nm, compared to 37% for the pure drug). Solubility and in vitro dissolution studies indicated that microencapsulation did not improve the dissolution pattern of RSV in simulated gastric and intestinal aqueous fluids. Evaluation of the in vitro antioxidant activity showed that, compared to the neat drug in aqueous solution, RSV loaded in the microspheres retained for a longer time, up to 22 days of incubation, the initial ORAC capacity. The present study thus demonstrated that Eudragit® Retard resins can be used to easily produce micro-sized solid dispersions with RSV, for potential oral administration, contributing to ameliorate the physico-chemical stability and antioxidant activity of this compound.

A Cheap and Convenient Method of Liposome Preparation Using Glass Beads as a Source of Shear Force.

Liposomes, the biocompatible lipid bilayer vesicles, have attracted immense attention due to their distinctive features such as efficient vehicle for the delivery of a wide range of therapeutic agents, adjustable formulation properties, and high drug entrapment efficiency. In this contribution, we present a simple method for the preparation of liposomes using glass beads and compared the potential of this method with conventional methods of liposome preparation. The prepared liposomes were characterized by different analytical techniques (HPLC, DLS, TEM, differential scanning calorimetry, and in vitro drug release). Our findings revealed that the particle size of liposomes is mainly dependent on the size of the glass beads and the glass bead shearing time. An average liposome size of 67.7 ± 25.5 nm was obtained using 2-mm glass beads after 24-h incubation at 200 rpm. The liposomes prepared under the optimized conditions exhibited a high encapsulation efficiency of 92.1 ± 1.7% with 31.08% drug release after 360 min at 37°C. In conclusion, the developed method is a simple and convenient process of liposome preparation of different sizes with desirable entrapment efficiency capacity.

Torsemide Fast Dissolving Tablets: Development, Optimization Using Box-Bhenken Design and Response Surface Methodology, In Vitro Characterization, and Pharmacokinetic Assessment.

The present study planed to develop new fast dissolving tablets (FDTs) of torsemide. Solid dispersions (SDs) of torsemide and sorbitol (3:1) or polyvinylpyrrolidone (PVP) k25 were prepared. The prepared SDs were evaluated for in-vitro dissolution. Fourier transform infrared spectroscopy and differential scanning calorimetry for SDs revealed no drug/excipient interactions and transformation of torsemide to the amorphous form. Torsemide/sorbitol SD was selected for formulation of torsemide FDTs by direct compression method. Box-Bhenken factorial design was employed to design 15 formulations using croscarmellose sodium and crospovidone at different concentrations. The response surface methodology was used to analyze the effect of changing these concentrations (independent variables) on disintegration time (Y1), percentage friability (Y2), and amount torsemide released at 10 min. The physical mixtures of torsemide and the used excipients were evaluated for angle of repose, Hausner's ratio, and Carr's index. The prepared FDTs tablets were evaluated for wetting and disintegration time, weight variation, drug content, percentage friability, thickness, hardness, and in vitro release. Based on the in-vitro results and factorial design characterization, F10 and F7 were selected for bioavailability studies following administration to Albino New Zealand rabbits. They showed significantly higher C max and (AUC0-12) and shorter T max than those obtained after administration of the corresponding ordinary commercial Torseretic ® tablets. Stability study was conducted for F10 that showed good stability upon storage at 30°C/75% RH and 40°C/75% RH for 3 months.

Assessment of the Dissociation Energetics of Some Selected Ligand Drugs Bound on Human Serum Albumin by Differential Scanning Calorimetry.

Drug-protein binding may play a role in the thermal energetics of protein denaturation and could lead to the determination of its equilibrium dissociation parameter. The aim of this study was to assess the energetics of a drug that was bound to human serum albumin (HSA) during thermal denaturation. Drugs that were bound at a single high-affinity primary binding site on HSA, including diazepam and ibuprofen, were employed. Commercial HSA was treated with charcoal to remove stabilizers and adjusted to 20% w/v in a pH 7.4 buffered solution. Serial concentrations of individual drugs up to 0.16 mmole/g-protein were added to the cleaned HSA solutions whereas diazepam was added to a commercial HSA solution. Samples were subjected to differential scanning calorimetry (DSC) set to run from 37 to 90°C at 3.0°C/min. Binding of the drug slightly increased the denaturing temperature of the cleaned HSA due to a shift in the equilibrium toward the native protein bound with the drug. Diazepam depressed the denaturing temperature of the commercial HSA by competing with the stabilizers already bound to the primary site of the HSA. This yielded not only the HSA-stabilizer but also the HSA-diazepam type complexes that exhibited a different denaturation process. A rational approximation of the Lumry-Eyring protein denaturation model was used to treat the DSC endotherms. The approximated scheme: [Formula: see text] was successfully fitted to the data. It was used to determine the dissociation parameters for diazepam and ibuprofen bound to the HSA. These results were comparable to those obtained from other methods.

Fabrication, solid state characterization and bioavailability assessment of stable binary amorphous phases of Ritonavir with Quercetin.

In the current study, Quercetin (QRT) was characterized for thermodynamic and kinetic parameters and found as an excellent glass former. QRT was paired with Ritonavir (RTV) (BCS class-IV antiretroviral) to form stable amorphous form and pharmacologically relevant combination. Binary amorphous forms of RTV and QRT in molar ratios 1:1, 1:2 and 2:1 were prepared by solvent evaporation technique and characterized by XRPD, DSC and FTIR. The prepared binary phases were found to become amorphous after solvent evaporation which was confirmed by disappearance of crystalline peaks from X-ray diffractograms and detecting single Tg in DSC studies. The physical stability studies at 40 °C for 90 days found RTV:QRT 1:2 and RTV:QRT 2:1 phases stable, while trace crystallinity was detected for 1:1M ratio. The temperature stability of RTV:QRT 1:2 and RTV:QRT 2:1 amorphous forms can be attributed to phase solubility of both components where the drug in excess acts as a crystallization inhibitor. Except for RTV:QRT 1:2 ratio, there was no evidence of intermolecular interactions between two components. Almost 5 fold increase in the saturation solubility was achieved for RTV, compared to crystalline counterpart. While for QRT, the solubility advantage was not achieved. In vivo oral bioavailability study was conducted for 1:2 binary amorphous form by using pure RTV as a control. Cmax was improved by 1.26 fold and Tmax was decreased by 2h after comparing with control indicating improved absorption. However no significant enhancement of oral bioavailability (1.12 fold after comparing with control) was found for RTV.

A rapid approach to the preliminary assessment of the physical stability of pharmaceutical hydrates.

Pharmaceutical hydrates have been used as clinical development candidates and in marketed products. The physical stability of hydrates can pose unique challenges to their development because of their particular sensitivity to the moisture levels in their surroundings. By conducting simple experiments early during the form selection phase of a drug candidate's development, a basic understanding of the thermodynamic and kinetic aspects of a hydrate form's stability can be attained that can facilitate the successful navigation of these challenges. Differential scanning calorimetry was used to determine the thermal and kinetic properties of a number of pharmaceutically relevant hydrates. The activation energy (E(a)) of dehydration and dehydration onset temperature (T(onset)) of survey compounds were compiled and analyzed. A significant number of compounds possessed both high E(a) and high T(onset) of dehydration, suggesting that these hydrate crystal forms were particularly stable. The results of these studies suggest that dehydration E(a) and dehydration T(onset) together can be used as early indicators of a crystalline hydrate's physical stability and can alert to potential challenges in developing hydrate crystal forms of drug candidates.

Assessment of crystalline disorder in cryo-milled samples of indomethacin using atomic pair-wise distribution functions.

The aim of this study was to investigate the usefulness of the atomic pair-wise distribution function (PDF) to detect the extension of disorder/amorphousness induced into a crystalline drug using a cryo-milling technique, and to determine the optimal milling times to achieve amorphisation. The PDF analysis was performed on samples of indomethacin obtained by cryogenic ball milling (cryo-milling) for different periods of time. X-ray powder diffraction (XRPD), differential scanning calorimetry (DSC), polarised light microscopy (PLM) and solid state nuclear magnetic resonances (ss-NMR) were also used to analyse the cryo-milled samples. The high similarity between the γ-indomethacin cryogenic ball milled samples and the crude γ-indomethacin indicated that milled samples retained residual order of the γ-form. The PDF analysis encompassed the capability of achieving a correlation with the physical properties determined from DSC, ss-NMR and stability experiments. Multivariate data analysis (MVDA) was used to visualize the differences in the PDF and XRPD data. The MVDA approach revealed that PDF is more efficient in assessing the introduced degree of disorder in γ-indomethacin after cryo-milling than MVDA of the corresponding XRPD diffractograms. The PDF analysis was able to determine the optimal cryo-milling time that facilitated the highest degree of disorder in the samples. Therefore, it is concluded that the PDF technique may be used as a complementary tool to other solid state methods and that further investigations are warranted to elucidate the capabilities of this technique.

Preformulative assessment of preformed complexes of gemfibrozil, with cyclodextrins.

The aim of this study is to carry out preformulative investigations on preformed inclusion complexes of the poorly water-soluble, lipid-lowering agent gemfibrozil and naturally occurring cyclodextrins (CDs). Phase solubility studies showed a linear AL- type diagram with alpha, beta, and y cyclodextrins, indicating the formation of inclusion complexes in a 1:1 molar ratio with all the three CDs. beta-CD-gemfibrozil complex having a maximum stability constant of 148.88 M(-1) was selected for preparation of preformed inclusion complex by kneading, co-precipitation, co-evaporation, and freeze-drying and compared with the physical mixture. The kneaded product was subjected to microwave-drying, with this mode of drying studied as an alternative method for preparation of the complex. The prepared complexes were assessed by equilibrium solubility analysis and intrinsic dissolution rate studies. Further characterization was done by differential scanning calorimetry, X-ray powder diffractometry, Fourier transform infrared spectroscopy, and scanning electron microscopy. The freeze-dried product was identified as the inclusion complex having the maximum intrinsic dissolution rate and hence was assessed for changes in permeability characteristics. pH partition studies and partial in vivo permeability studies showed no changes in the permeability of the freeze-dried product when compared to the pure drug.

Effect of processing on Celecoxib and its solvates.

Pharmaceuticals mostly exist in crystalline form and exhibit the phenomenon of differential crystal packing and configurational arrangements of molecules, called polymorphism. Pharmaceutical processing by introducing significant amount of stress alters the molecular interactions in the system engendering polymorphic transformations. The energy supplied by these processing steps tends to overcome the energy barriers between different solid-state forms, thus yielding undesirable changes in the physicochemical and material characteristics of drugs or their dosage forms. Therefore, the role of these unit processes in solid-state transformations must be cautiously studied and if required appropriate controls should be used to monitor such events. The present study was aimed at studying the effect of major energy imparting pharmaceutical unit processes, like size reduction, wet granulation, consolidation, and compression on solid-state transformation of Celecoxib, a selective cyclooxygenase-II inhibitor and its N,N-dimethyl acetamide and N,N-dimethyl formamide solvated forms. A qualitative estimation of crystal transformation in processed samples was performed using DSC, microscopy, FTIR spectroscopy, and XRPD. FTIR was also applied for the development of a quantification method to find the percentage of transformation in N,N-dimethyl acetamide solvated form during compression.

Assessment of degree of disorder (amorphicity) of lyophilized formulations of growth hormone using isothermal microcalorimetry.

When determining the degree of disorder of a lyophilized cake of a protein, it is important to use an appropriate analytical technique. Differential scanning calorimetry (DSC) and X-ray powder diffraction (XRPD) are the most commonly used thermoanalytical techniques for characterizing freeze-dried protein formulations. Unfortunately, these methods are unable to detect solid-state disorder at levels < 10%. Also, interpretation of DSC results for freeze-dried protein formulations can be difficult, as a result of the more complex thermal events occurring with this technique. For example, proteins can inhibit the thermally induced recrystallization of the lyophilized cake, resulting in potential misinterpretation of DSC degree of disorder results. The aim of this investigation was to study the use of isothermal microcalorimetry (IMC) in the assessment of degree of solid-state disorder (amorphicity) of lyophilized formulations of proteins. For this purpose, two formulations of growth hormone were prepared by lyophilization. These formulations consisted of the same amounts of protein, mannitol, glycine, and phosphate buffer, but differed in the freeze-drying procedure. After lyophilization, the recrystallization of the samples was studied using IMC at 25 degrees C under different relative humidities (58-75%). The effect of available surface area was studied by determining the heat of recrystallization (Q) of the samples before and after disintegration of the cakes. The results showed that, in contrast to DSC, IMC allowed detection of the recrystallization event in the formulations. Although both formulations were completely disordered and indistinguishable according to XRPD method, IMC revealed that formulation B had a different solid-sate structure than formulation A. This difference was the result of differences in the freeze-drying parameters, demonstrating the importance of choosing appropriate analytical methodology.

New approach to stability assessment of protein solution formulations by differential scanning calorimetry.

A central composite rotate second order design was used to evaluate chicken egg-white lysozyme (lysozyme) thermal stability at different pH, and lysozyme, sucrose and 2-hydroxypropyl-beta-cyclodextrin (HPbetaCD) concentrations, by means of differential scanning calorimetry (DSC). Four measurements were used to characterize the thermogram: the calorimetric enthalpy (DeltaH(cal)), the temperature at maximum heat flux (T(m)), the ratio of maximum heat flux over thermogram area (C(pT(m))/area), and the ratio of calorimetric enthalpies from the second heating cycle to the first enthalpy (R(DeltaH(cal))). These parameters were interpreted using the three step equilibrium model for protein degradation (irreversible degradation following reversible unfolding). In addition to degradation, increased lysozyme concentration leads to a sizeable decrease in DeltaH(cal) and area ratio, showing how it causes protein aggregation; which in turn promotes protein degradation. DeltaH(cal) and T(m) reach maxima at pH 5, R(DeltaH(cal)) at pH 4.19, while C(pT(m))/area increases linearly with pH, revealing a specific base catalysis of the irreversible degradation step. The role of sucrose concentration in lysozyme stabilization is linked to the stabilization of the unfolded moiety; it neither affects DeltaH(cal) nor C(pT(m))/area, but increases both T(m) and R(DeltaH(cal)). No influence of HPbetaCD on the stability of lyzozyme was observed, probably due to low concentrations employed.

Assessment of solid-state interactions of naproxen with amorphous cyclodextrin derivatives by DSC.

A microcalorimetric method based on differential scanning calorimetry (DSC) of drug-additive binary systems to assess kneading-induced interactions was applied to naproxen (NAP) in combinations with amorphous hydroxypropyl beta-cyclodextrin (HPbetaCd), beta-cyclodextrin sulfobutyl ether, sodium salt ((SBE)(7m)-betaCd), acetyl beta-cyclodextrin (AcbetaCd) and acetyl gamma-cyclodextrin (AcgammaCd). Modifications of thermal parameters of NAP in DSC curves of physical mixtures indicate heating-induced interactions which resulted in a broadening of the NAP melting endotherm in the combinations with HPbetaCd, AcbetaCd and AcgammaCd. The effect of kneading on the interaction was particularly pronounced for the NAP-HPbetaCd and NAP-(SBE)(7m)-betaCd systems, which show a similar drug-to-carrier interaction ratio (1:2 by weight) as that of the other systems. Drug-to-carrier ratios, calculated considering the amount of NAP which recrystallizes from the melted mixtures equivalent to NAP not bound to the carrier, show a distinctly lower affinity in solid-state of the drug for the anionically charged (SBE)(7m)-betaCd with respect to other neutral carriers. The similar affinity of NAP for AcbetaCd and AcgammaCd demonstrates that the geometry of the cavity, which is a determinant factor for the inclusion complexation in liquid state, does not influence the interaction process in solid-state.

Cryogenic grinding of indomethacin polymorphs and solvates: assessment of amorphous phase formation and amorphous phase physical stability.

The effect of cryogenic grinding on five crystal forms of indomethacin (IMC) was investigated with particular interest in the formation of amorphous phase. Powder X-ray diffraction (PXRD) and differential scanning calorimetry (DSC) demonstrated that amorphous phase formation took place for all three polymorphs (gamma, alpha, and delta) and one solvate (IMC methanolate). In the latter case, a postgrinding drying stage was needed to remove desolvated methanol from the ground amorphous product because methanol destabilized amorphous IMC presumably via a plasticizing effect. The crystal structure of another solvate, IMC t-butanolate, was unaffected by grinding, indicating that amorphous phase formation on grinding does not occur in all cases. Ground amorphous materials possessed similar glass transition temperatures but significant differences in physical stability as assessed by both isothermal and nonisothermal crystallization. It is argued that physical factors, namely residual crystal phase and specific surface area, determine the isothermal and nonisothermal crystallization behavior of ground amorphous samples as opposed to intrinsic differences in the structure of the amorphous phase.

[Caloric surface and assessment of the caloric bithermal test. Toward an intelligent system of vestibular diagnosis]. / La superficie calórica en la valoración de la prueba calórica bitérmica: hacia un sistema inteligente de diagnóstico vestibular.

The theoretical basis for bithermal caloric test assessment by means of caloric surfaces is described. This system supports a computer program for the automatic appraisal of the test, as a first step in the development of our intelligent system for vestibular diagnosis.