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Physical Mixture (physical + mixture)
Selected AbstractsEffect of molecular weight, temperature, and additives on the moisture sorption properties of polyethylene glycolJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 1 2010Jared A. Baird Abstract Polyethylene glycol (PEG) is a hygroscopic polymer that undergoes the phenomenon of deliquescence once a critical relative humidity (RH0) is reached. The purpose of this study was to test the hypothesis that the deliquescence behavior of PEG will be affected by the polymer molecular weight, temperature, and the presence of additives. The deliquescence relative humidity for single component (RH0) and binary mixtures (RH0,mix) were measured using an automated gravimetric moisture analyzer at 25 and 40°C. Changes in PEG crystallinity after exposure to moisture were qualitatively assessed using powder X-ray diffraction (PXRD). Optical microscopy was used to visually observe the deliquescence phenomenon. For single component systems, decreasing PEG MW and elevating the temperature resulted in a decrease in the observed RH0. Physical mixtures of acetaminophen and anhydrous citric acid with both PEG 3350 and PEG 100,000 exhibited deliquescence (RH0,mix) at a relative humidity below that of either individual component. Qualitative changes in crystallinity were observed from the X-ray diffractograms for each PEG MW grade at high relative humidities, indicating that phase transformation (deliquescence) of the samples had occurred. In conclusion, it was found that the deliquescence behavior of PEG was affected by the polymer MW, temperature, and the presence of additives. This phenomenon may have important implications for the stability of PEG containing formulations. © 2009 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 99:154,168, 2010 [source] Improved physical stability of amorphous state through acid base interactionsJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 6 2009Chitra Telang Abstract To investigate role of specific interactions in aiding formation and stabilization of amorphous state in ternary and binary dispersions of a weakly acidic drug. Indomethacin (IMC), meglumine (MU), and polyvinyl pyrollidone (PVP) were the model drug, base, and polymer, respectively. Dispersions were prepared using solvent evaporation. Physical mixtures were cryogenically coground. XRPD, PLM, DSC, TGA, and FTIR were used for characterization. MU has a high crystallization tendency and is characterized by a low Tg (17°C). IMC crystallization was inhibited in ternary dispersion with MU compared to IMC/PVP alone. An amorphous state formed readily even in coground mixtures. Spectroscopic data are indicative of an IMC,MU amorphous salt and supports solid-state proton transfer. IMC,MU salt displays a low Tg,,,50°C, but is more physically stable than IMC, which in molecular mixtures with MU, resisted crystallization even when present in stoichiometric excess of base. This is likely due to a disrupted local structure of amorphous IMC due to specific interactions. IMC showed improved physical stability on incorporating MU in polymer, in spite of low Tg of the base indicating that chemical interactions play a dominant role in physical stabilization. Salt formation could be induced thermally and mechanically. © 2008 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 98:2149,2159, 2009 [source] Process induced disorder in crystalline materials: Differentiating defective crystals from the amorphous form of griseofulvinJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 8 2008Tao Feng Abstract This research investigates milling induced disorder in crystalline griseofulvin. Griseofulvin was subjected to cryogenic milling for various lengths of time. For comparison, the amorphous form of griseofulvin was also prepared by the quench melt method. Different analytical techniques were used to study the differences between the cryomilled, amorphous and crystalline forms of the drug. Cryogenic milling of griseofulvin progressively reduces the crystallinity of the drug by inducing crystal defects, rather than amorphous materials. Raman analysis provides evidence of structural differences between the two. The differences between the defective crystals produced by milling and the amorphous form are significant enough as to be measurable in their bulk thermal properties. Defective crystals show significant decrease in the heat of fusion as a function of milling time but do not exhibit a glass transition nor recrystallization from the amorphous form. Crystal defects undergo recrystallization upon heating at temperatures well below the glass transition temperature (Tg) in a process that is separate and completely independent from the crystallization of the amorphous griseofulvin, observed above Tg. Physical mixtures of defective crystals and amorphous drug demonstrate that the thermal events associated with each form persist in the mixtures, unaffected by the presence of the other form. © 2007 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 97: 3207,3221, 2008 [source] Selectivity effects on series reactions by reactant storage and PSA operationAICHE JOURNAL, Issue 11 2000Adriaan J. Kodde This work evaluates adsorptive reactors used to improve the operation of a sequential reaction scheme, , for the total removal of A from a stream with an excess of B. In the adsorptive-reactor concept, the reactor is filled with a physical mixture of catalyst and an adsorbent, the latter being thermodynamically selective toward primary reactant A. In this case, the sorbent is periodically regenerated using the principles of pressure swing adsorption and purged with secondary reactant D. This concept is restricted to low temperatures to have sufficient adsorption capacity. Improved reaction selectivity arises from the accumulation of A in the unit. The reaction of A maximizes the driving force for regeneration and thus accelerates the regeneration half-cycle. The adsorptive reactor is compared to a conventional plug-flow reactor (PFR) and to PSA and PFR units in series. Reaction selectivity improved and pure B recovered over these alternative reactors under realistic conditions. The volume-based productivity is lower than that of PFR, but higher than that of PSA. The purge-gas flow rate can be manipulated to balance the sorption flux and reaction rate, thereby maximizing the conversion of A. The influence of differences in sorption kinetics is discussed and the required sorbent characteristics are identified. [source] Characterisation of an inclusion complex between cladribine and 2-hydroxypropyl-,-cyclodextrin,JOURNAL OF PHARMACEUTICAL SCIENCES, Issue 9 2008Valeria Van Axel Castelli Abstract Parenterally administered cladribine (2-chloro-2,-deoxyadenosine) has demonstrated promising efficacy and safety in clinical trials in patients with multiple sclerosis (MS). An oral formulation of this small molecule would be an attractive option for patients. Here, we describe the chemical characterisation of the inclusion complex between cladribine and the drug carrier molecule 2-hydroxypropyl-,-cyclodextrin (2-HP-,-CD). Several techniques were used to analyse the complex both in solution and in the solid state. These analyses provided evidence that the inclusion complex cannot be simply reduced to the sum of the two species, as it shows behaviour different from that of the physical mixture of the two components. Furthermore, solution nuclear magnetic resonance spectroscopy demonstrated the existence of an inclusion complex between cladribine and 2-HP-,-CD. Importantly, analysis of a tablet formulation demonstrated that the chemical characteristics of the inclusion complex are not affected by the manufacturing process, and that the complex is stable during storage. This tablet formulation is currently under investigation for the treatment of patients with MS. © 2008 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 97:3897,3906, 2008 [source] Ultrasound-compacted indomethacin/polyvinylpyrrolidone systems: Effect of compaction process on particle morphology and dissolution behaviorJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 8 2002Adamo Fini Abstract Indomethacin (IMC)/polyvinylpyrrolidone systems were prepared under different technological conditions, using co-evaporation, kneading, traditional, and ultrasound (US) compaction. The materials thus obtained were milled and sieved and the powders were analyzed by using scanning electron microscopy to evaluate the morphology of the final particles and the fractal dimension of the particle contour. In the case of US-treated particles, scanning electron micrographs suggest that IMC could have partially covered the excipient granule surface, which appears lustrous and smooth, whereas after co-evaporation, the particles display a stratified structure. The external color of the granules, the hot stage microscopy examination, and the absence of the melting peak of the drug in thermograms supports the idea that IMC converts into an amorphous form under US discharge. Each technological treatment performed on the binary mixtures increases the dissolution rate of the drug, with respect to the pure drug and the physical mixture, but to a lesser extent than US compaction. US compaction and co-evaporation produce comparable results in improving the release of the drug. Polyvinylpyrrolidone offers better results than ,-cyclodextrin in promoting the dissolution of IMC, when both systems are compacted under US. © 2002 Wiley-Liss Inc. and the American Pharmaceutical Association J Pharm Sci 91:1880,1890, 2002 [source] Improvement of dissolution and oral absorption of ER-34122, a poorly water-soluble dual 5-lipoxygenase/cyclooxygenase inhibitor with anti-inflammatory activity by preparing solid dispersionJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 1 2002Ikuo Kushida Abstract Several formulation approaches were attempted to improve the dissolution and the oral absorption of ER-34122, which is a novel dual 5-lipoxygenase/cyclooxygenase inhibitor with potent anti-inflammatory activity. The solid dispersion of ER-34122 with hydroxypropylmethylcellulose (TC-5RW), which is an inert solid carrier, resulted in a significant improvement in the dissolution rate of ER-34122. The solid dispersion was prepared by a solvent evaporation method using ethanol and water. The solid-state characteristics of the solid dispersion, the corresponding physical mixture, and ER-34122 alone were investigated by X-ray powder diffraction, Fourier transform infrared spectroscopy (FTIR), and an automated controlled-atmosphere microbalance. The X-ray powder diffraction patterns suggest that the solid dispersion exists in a totally amorphous state and the others exist in a crystalline state. The FTIR spectra results suggest that ER-34122 can interact with TC-5RW through intermolecular hydrogen bonding in the solid dispersion. This interaction may cause a stabilization of ER-34122 in the higher-energy, faster-dissolving amorphous state. The dissolution rate of ER-34122 from the solid dispersion was significantly greater than that from the physical mixture or the pure drug. Furthermore, when orally administrated to beagle dogs, ER-34122 showed about a 100-fold increase in both maximum concentration (Cmax) and area under the curve of concentration versus time (AUC) compared with the pure drug. Consequently, it was determined that the solid dispersion technique with TC-5RW provides a promising way to increase the dissolution rate and the oral absorption of poorly water-soluble drugs such as ER-34122. © 2002 Wiley-Liss, Inc. and the American Pharmaceutical Association J Pharm Sci 91:258,266, 2002 [source] Cefuroxime axetil solid dispersions prepared using solution enhanced dispersion by supercritical fluidsJOURNAL OF PHARMACY AND PHARMACOLOGY: AN INTERNATI ONAL JOURNAL OF PHARMACEUTICAL SCIENCE, Issue 12 2005Seoung Wook Jun Cefuroxime axetil (CA) solid dispersions with HPMC 2910/PVP K-30 were prepared using solution enhanced dispersion by supercritical fluids (SEDS) in an effort to increase the dissolution rate of poorly water-soluble drugs. Their physicochemical properties in solid state were characterized by differential scanning calorimeter (DSC), powder X-ray diffraction (PXRD), Fourier transform infrared spectrometry (FT-IR) and scanning electron microscopy. No endothermic and characteristic diffraction peaks corresponding to CA were observed for the solid dispersions in DSC and PXRD. FTIR analysis demonstrated the presence of intermolecular hydrogen bonds between CA and HPMC 2910/PVP K-30 in solid dispersions, resulting in the formation of amorphous or non-crystalline CA. Dissolution studies indicated that the dissolution rates were remarkably increased in solid dispersions compared with those in the physical mixture and drug alone. In conclusion, an amorphous or non-crystalline CA solid dispersion prepared using SEDS could be very useful for the formulation of solid dosage forms. [source] Tetanus toxoid-loaded transfersomes for topical immunizationJOURNAL OF PHARMACY AND PHARMACOLOGY: AN INTERNATI ONAL JOURNAL OF PHARMACEUTICAL SCIENCE, Issue 3 2005Prem N. Gupta Topical immunization is a novel immunization strategy by which antigens and adjuvants are applied topically to intact skin to induce potent antibody and cell-mediated responses. Among various approaches for topical immunization, the vesicular approach is gaining wide attention. Proteineous antigen alone or in combination with conventional bioactive carriers could not penetrate through the intact skin. Hence, specially designed, deformable lipid vesicles called transfersomes were used in this study for the non-invasive delivery of tetanus toxoid (TT). Transfersomes were prepared and characterized for shape, size, entrapment efficiency and deformability index. Fluorescence microscopy was used to investigate the mechanism of vesicle penetration through the skin. The immune stimulating activity of these vesicles was studied by measuring the serum anti-tetanus toxoid IgG titre following topical immunization. The immune response was compared with the same dose of alum adsorbed tetanus toxoid (AATT) given intramuscularly, topically administered plain tetanus toxoid solution, and a physical mixture of tetanus toxoid and transfersomes again given topically. The results indicated that the optimal transfersomal formulation had a soya phosphatidylcholine and sodium deoxycholate ratio of 85:15%, w/w. This formulation showed maximum entrapment efficiency (87.34±3.81%) and deformability index (121.5±4.21). An in-vivo study revealed that topically administered tetanus toxoid-loaded transfersomes, after secondary immunization, elicited an immune response (anti-TT-IgG) comparable with that produced by intramuscular AATT. Fluorescence microscopy revealed the penetration of transfersomes through the skin to deliver the antigen to the immunocompetent Langerhans cells. [source] Microwave-Assisted Synthesis of Fine Particle Oxides Employing Wet Redox MixturesJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 10 2002Solomon Sundar Manoharan Interaction of electromagnetic radiation with a physical mixture of metal nitrates and amides/hydrazides is observed to initiate high-temperature reactions, useful for realizing several high-temperature ceramic materials. A judicious choice of such redox mixtures undergoes exothermic reactions when they couple with microwave radiation. The coupling of electromagnetic radiation with metal salts and amides/hydrazides depends on the dielectric properties of the individual components in the reaction mixture. The approach has been used to prepare ,-Fe2O3, Fe3O4, MgCr2O4, ,-CaCr2O4, and La0.7Ba0.3MnO3. [source] Partially hydrolyzed kappa carrageenan,polyacrylonitrile as a novel biopolymer-based superabsorbent hydrogel: Synthesis, characterization, and swelling behaviorsPOLYMER ENGINEERING & SCIENCE, Issue 12 2006M. T. Savoji In this paper, synthesis and swelling behavior of a novel superabsorbent hydrogel based on kappa carrageenan (,C) and polyacrylonitrile (PAN) was investigated. To achieve partially hydrolyzed ,C-PAN hydrogel, physical mixture of ,C and PAN was hydrolyzed by NaOH solution. During alkaline hydrolysis, the nitrile groups of PAN are converted to a mixture of hydrophilic carboxamide and carboxylate groups follow by in situ crosslinking of the grafted PAN chains. The reaction variables affecting on the swelling capacity of the hydrogel were systematically optimized to achieve a hydrogel with swelling capacity as high as possible. Under the optimized conditions concluded, super swelling hydrogel with the ability of water absorption up to 3260 g/g (water/dry hydrogel powder) has been prepared. Swelling measurements of the synthesized hydrogels was carried out in various salt solutions and solutions with different pH. The results indicate that the hydrogels have good pH sensitivity and pH-reversible property between pH 2 and pH 8. POLYM. ENG. SCI. 46:1778,1786, 2006. © 2006 Society of Plastics Engineers. [source] Effect of chirality on PVP/drug interaction within binary physical mixtures of ibuprofen, ketoprofen, and naproxen: A DSC studyCHIRALITY, Issue 8 2009Ivan T. Ivanov Abstract We report on the thermal behavior of freshly prepared binary drug/polymer physical mixtures that contained ibuprofen, ketoprofen, or naproxen as a drug, and polyvinylpyrrolidone (PVP), hydroxyethylcellulose (HEC), or methylcellulose (MC) as excipient. At 6,10°C/min heating rates the DSC detected a sharp, single endotherm that corresponds to the melting of drug. On heating physical mixtures of PVP and racemic ibuprofen or ketoprofen at lower heating rates, another endotherm was registered in front of the original one. To observe the additional endotherm, specific minimal values of the heating rate and of PVP weight fraction were needed; for ibuprofen and ketoprofen they were 1.5 and 2.0°C/min, and 5 and 15% (w/w), respectively. At greater PVP weight fractions the top temperatures, Tmp, of both peaks were reduced almost linearly indicating strong solid-state interfacial reaction between the drug particles and PVP matrix. The additional endotherm was abolished at greater heating rates (2°C/min for ibuprofen, 3°C/min for ketoprofen), by replacing the racemate with respective S(+)-enantiomer and by replacing PVP with HEC and MC. Hence, the possible inclusion of enantioselective component within the PVP/drug interaction, responsible for the amorphization of physical mixture over storage, is assumed. Chirality, 2009. © 2008 Wiley-Liss, Inc. [source] Transforming powder mechanical properties by core/shell structure: Compressible sandJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 11 2010Limin Shi Abstract Some active pharmaceutical ingredients possess poor mechanical properties and are not suitable for tableting. Using fine sand (silicon dioxide), we show that a core/shell structure, where a core particle (sand) is coated with a thin layer of polyvinylpyrrolidone (PVP), can profoundly improve powder compaction properties. Sand coated with 5% PVP could be compressed into intact tablets. Under a given compaction pressure, tablet tensile strength increases dramatically with the amount of coating. This is in sharp contrast to poor compaction properties of physical mixtures, where intact tablets cannot be made when PVP content is 20% or less. The profoundly improved tabletability of core/shell particles is attributed to the formation of a continuous three-dimensional bonding network in the tablet. © 2010 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 99:4458,4462, 2010 [source] A solid-state NMR study of phase structure, molecular interactions, and mobility in blends of citric acid and paracetamolJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 5 2009S. Schantz Abstract Citric acid anhydrate (CAA) and paracetamol (PARA), prepared as crystalline physical mixtures and as amorphous blends, were studied using 13C solid-state cross polarization magic angle spinning (CPMAS) NMR. Amorphous blends showed significant line broadening from the conformational distribution as compared to the crystalline samples. Also, chemical shift variations were observed between crystalline and amorphous blends, which were attributed to differences in intermolecular interactions. Averaging of proton rotating-frame spin-lattice relaxation times (T1,) probed via different 13C sites in the amorphous blends confirmed molecular level mixing. For some, initially amorphous, sample compositions the onset of crystallization was evident directly from spectra and from the significantly longer T1, relaxations. Thus, crystallization caused phase separation with properties of the two phases resembling those of pure CAA and PARA, respectively. 13C spectra of amorphous 50/50 (w/w, %) CAA/PARA recorded from above the glass transition temperature broadened as the temperature increased to a maximum at T,,,Tg,+,33 K. This was the result of a dynamic interference between the line narrowing techniques being applied and the time scale of molecular reorientation in the miscible melt. The derived average correlation time was found to correspond well with previous results from melt rheology. We conclude that the underlying reasons for physical instability (i.e., crystallization from the miscible melt, including molecular interactions and dynamics) of this class of amorphous binary mixtures can be effectively evaluated using NMR spectroscopy. © 2008 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 98:1862,1870, 2009 [source] Practical considerations in development of solid dosage forms that contain cyclodextrinJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 7 2007Lee A. Miller Abstract The following is a review of the literature that addresses the use of cyclodextrin in solid dosage forms. Care was taken to exclude physical and chemical characteristics of cyclodextrin, which have been discussed in the literature. A flow diagram is provided to outline the decision-making steps that are involved in the development process. Both preparation of physical mixtures and inclusion complexes are considered. Analytical techniques to determine the presence of inclusion complexes, the effect of other excipients on complex formation, the effect of size limitation of solid dosages forms, powder processing, and storage of solid dosage forms are discussed. © 2007 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 96: 1691,1707, 2007 [source] Effect of cyclodextrins on the solubility and antimycotic activity of sertaconazole: Experimental and computational studiesJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 11 2002I. Perdomo-López Abstract This study investigated the effects of the complexation of sertaconazole nitrate with different cyclodextrin (CD) derivatives (,-CD, ,-CD, ,-CD, hydroxypropyl-,-CD, and hydroxypropyl-,-CD) on the aqueous solubility and antimycotic activity of the drug. Phase solubility studies indicated that the solubility of sertaconazole in enzyme-free simulated gastric- and enzyme-free simulated enteric fluids was significantly increased in the presence of cyclodextrins. The observed order of solubility increasing effect was: ,-CD,>,HP,-CD,>,HP,-CD,>,,-CD,>,,-CD. Solid-state sertaconazole,cyclodextrin complexes were prepared by freeze drying, and characterized by X-ray powder difractometry, differential scanning calorimetry (DSC), and infrared spectroscopy (FTIR). Freeze-dried complexes showed markedly higher solubility than both physical mixtures and sertaconazole alone. The antimycotic activities of sertaconazole,cyclodextrin complexes in solution were evaluated by inhibition zone assays with Candida albicans. The activity ranking agrees with the solubility ranking observed for these complexes, with the ,-CD,sertaconazole complex showing the strongest antimycotic activity. Finally, molecular modeling studies were carried out using the MM2 force field method, for complexes in vacuum and in water. This enable indentification of the preferred orientation of sertaconazole in the ,-CD cavity and of the main structural features responsible for the enhancement of its solubility and antimycotic activity. © 2002 Wiley-Liss, Inc. and the American Pharmaceutical Association J Pharm Sci 91:2408,2415, 2002 [source] Characterization of glass solutions of poorly water-soluble drugs produced by melt extrusion with hydrophilic amorphous polymersJOURNAL OF PHARMACY AND PHARMACOLOGY: AN INTERNATI ONAL JOURNAL OF PHARMACEUTICAL SCIENCE, Issue 3 2001Angus Forster Indomethacin, lacidipine, nifedipine and tolbutamide are poorly soluble in water and may show dissolution-related low oral bioavailability. This study describes the formulation and characterization of these drugs as glass solutions with the amorphous polymers polyvinylpyrrolidone (PVP) and polyvinylpyrrolidone-co-vinyl acetate by melt extrusion. The extrudates were compared with physical mixtures of drug and polymer. X-ray powder diffraction, thermal analysis, infrared spectroscopy, scanning electron microscopy, HPLC, moisture analysis and dissolution were used to examine the physicochemical properties and chemical stability of the glass solutions prepared by melt extrusion at a 1:1 drug/polymer ratio. Depending on the temperature used, melt extrusion produced amorphous glass solutions, with markedly improved dissolution rates compared with crystalline drug. A significant physicochemical interaction between drug and polymer was found for all extrudates. This interaction was caused by hydrogen bonding (H-bonding) between the carbonyl group of the pyrrole ring of the polymer and a H-donor group of the drug. Indomethacin also showed evidence of H-bonding when physical mixtures of amorphous drug and PVP were prepared. After storage of the extrudates for 4,8 weeks at 25°C/75% relative humidity (RH) only indomethacin/polymer (1:1) extrudate remained totally amorphous. All extrudates remained amorphous when stored at 25°C/< 10% RH. Differences in the physical stability of drug/polymer extrudates may be due to differences in H-bonding between the components. [source] Thermal Decomposition of Energetic Materials 85: Cryogels of Nanoscale Hydrazinium Diperchlorate in Resorcinol-FormaldehydePROPELLANTS, EXPLOSIVES, PYROTECHNICS, Issue 2 2003Bryce Abstract The objective of this work was to try to desensitize an energetic material by using sol-gel processing and freeze drying to incorporate the energetic material into the fuel matrix on the nano (or at least submicron) particle size scale. Hydrazinium diperchlorate ([N2H6][ClO4]2 or HP2) and resorcinol-formaldehyde (RF) were chosen as the oxidizer and fuel, respectively. Solid loading up to 88% HP2 was achieved by using the sol gel-to-cryogel method. Various weight percentages of HP2 in RF were characterized by elemental analysis, scanning electron (SEM) and optical microscopy, T-jump/FTIR spectroscopy, DSC, and drop-weight impact. SEM indicated that 20,50,nm diameter HP2 plates aggregated into porous 400,800,nm size clusters. Below 80% HP2 the cryogels are less sensitive to impact than physical mixtures having the same ratios of HP2 and RF. The decomposition temperatures of the cryogels are higher than that of pure HP2, which is consistent with their lower impact sensitivity. The heat of decomposition as measured at a low heating rate increases with increasing percentage of HP2. The cryogels and physical mixtures release similar amounts of energy, but the cryogels exhibit mainly a single exotherm by DSC whereas the physical mixtures showed a two-step energy release. Flash pyrolysis revealed gaseous product ratios suggestive of more energy being released from the cryogels than the physical mixtures. Cryogels also burn faster by visual observation. [source] Effect of chirality on PVP/drug interaction within binary physical mixtures of ibuprofen, ketoprofen, and naproxen: A DSC studyCHIRALITY, Issue 8 2009Ivan T. Ivanov Abstract We report on the thermal behavior of freshly prepared binary drug/polymer physical mixtures that contained ibuprofen, ketoprofen, or naproxen as a drug, and polyvinylpyrrolidone (PVP), hydroxyethylcellulose (HEC), or methylcellulose (MC) as excipient. At 6,10°C/min heating rates the DSC detected a sharp, single endotherm that corresponds to the melting of drug. On heating physical mixtures of PVP and racemic ibuprofen or ketoprofen at lower heating rates, another endotherm was registered in front of the original one. To observe the additional endotherm, specific minimal values of the heating rate and of PVP weight fraction were needed; for ibuprofen and ketoprofen they were 1.5 and 2.0°C/min, and 5 and 15% (w/w), respectively. At greater PVP weight fractions the top temperatures, Tmp, of both peaks were reduced almost linearly indicating strong solid-state interfacial reaction between the drug particles and PVP matrix. The additional endotherm was abolished at greater heating rates (2°C/min for ibuprofen, 3°C/min for ketoprofen), by replacing the racemate with respective S(+)-enantiomer and by replacing PVP with HEC and MC. Hence, the possible inclusion of enantioselective component within the PVP/drug interaction, responsible for the amorphization of physical mixture over storage, is assumed. Chirality, 2009. © 2008 Wiley-Liss, Inc. 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