Investigating the effect of moisture protection on solid-state stability and dissolution of fenofibrate and ketoconazole solid dispersions using PXRD, HSDSC and Raman microscopy

Enhanced dissolution of poorly soluble active pharmaceutical ingredients (APIs) in amorphous solid dispersions often diminishes during storage due to moisture-induced re-crystallization. This study aims to investigate the influence of moisture protection on solid-state stability and dissolution profiles of melt-extruded fenofibrate (FF) and ketoconazole (KC) solid dispersions. Samples were kept in open, closed and Activ-vials(?) to control the moisture uptake under accelerated conditions. During 13-week storage, changes in API crystallinity were quantified using powder X-ray diffraction (PXRD) (Rietveld analysis) and high sensitivity differential scanning calorimetry (HSDSC) and compared with any change in dissolution profiles. Trace crystallinity was observed by Raman microscopy, which otherwise was undetected by PXRD and HSDSC. Results showed that while moisture protection was ineffective in preventing the re-crystallization of amorphous FF, KC remained X-ray amorphous despite 5% moisture uptake. Regardless of the degree of crystallinity increase in FF, the enhanced dissolution properties were similarly diminished. Moisture uptake above 10% in KC samples also led to re-crystallization and significant decrease in dissolution rates. In conclusion, eliminating moisture sorption may not be sufficient in ensuring the stability of solid dispersions. Analytical quantification of API crystallinity is crucial in detecting subtle increase in crystallinity that can diminish the enhanced dissolution properties of solid dispersions.     

Characteristics of bicalutamide solid dispersions and improvement of the dissolution

The purpose of our study was to formulate and evaluate bicalutamide (BL) solid dispersions (SD). The physicochemical properties were evaluated by differential scanning calorimetry (DSC), Fourier-Transform infrared (FT-IR) spectroscopy, Powder X-ray diffractometry (PXRD), dissolution studies, and stability studies. The dissolution studies demonstrated that the dissolution of BL from BL-SD increased with an increase in carrier content (PVP K30). X-ray assays and DSC results both confirmed the amorphous state of BL in BL-SD. Stability studies conducted after 6 months showed that BL exhibited excellent stability in the solid dispersion of PVP K30 (1:5).     

Preparation of budesonide-poly (ethylene oxide) solid dispersions using supercritical fluid technology

The purpose of this study was to investigate the possibility of preparing solid dispersions of the poorly soluble budesonide by supercritical fluid (SCF) technique, using poly (ethylene oxide) (PEO) as a hydrophilic carrier. The budesonide-PEO solid dispersions were prepared, using supercritical carbon dioxide (SC CO₂) as the processing medium, and characterized by scanning electron microscopy (SEM), powder X-ray diffraction (PXRD), differential scanning calorimetry (DSC), solubility test and dissolution test in order to understand the influence of the SCF process on the physical status of the drug. The endothermic peak of budesonide in the SCF-treated mixtures was significantly reduced, indicating that budesonide was in amorphous form inside the carrier system. This was further confirmed by SEM and PXRD studies. The enhanced dissolution rates of budesonide were observed from SCF-treated budesonide-PEO mixtures. The amorphous characteristic of the budesonide, the better mixing of drug and PEO powders in the presence of SC CO₂, together with the improved wettability of the drug in PEO, produced a remarkable enhancement of the in vitro drug dissolution rate. Thus, budesonide-PEO solid dispersions with enhanced dissolution rate can be prepared using organic solvent-free SCF process.     

Characteristics of Bicalutamide Solid Dispersions and Improvement of the Dissolution

ABSTRACT

The purpose of our study was to formulate and evaluate bicalutamide (BL) solid dispersions (SD). The physicochemical properties were evaluated by differential scanning calorimetry (DSC), Fourier-Transform infrared (FT-IR) spectroscopy, Powder X-ray diffractometry (PXRD), dissolution studies, and stability studies. The dissolution studies demonstrated that the dissolution of BL from BL-SD increased with an increase in carrier content (PVP K30). X-ray assays and DSC results both confirmed the amorphous state of BL in BL-SD. Stability studies conducted after 6 months showed that BL exhibited excellent stability in the solid dispersion of PVP K30 (1:5).     

Preparation of Budesonide-Poly (Ethylene Oxide) Solid Dispersions Using Supercritical Fluid Technology

The purpose of this study was to investigate the possibility of preparing solid dispersions of the poorly soluble budesonide by supercritical fluid (SCF) technique, using poly (ethylene oxide) (PEO) as a hydrophilic carrier. The budesonide-PEO solid dispersions were prepared, using supercritical carbon dioxide (SC CO₂) as the processing medium, and characterized by scanning electron microscopy (SEM), powder X-ray diffraction (PXRD), differential scanning calorimetry (DSC), solubility test and dissolution test in order to understand the influence of the SCF process on the physical status of the drug. The endothermic peak of budesonide in the SCF-treated mixtures was significantly reduced, indicating that budesonide was in amorphous form inside the carrier system. This was further confirmed by SEM and PXRD studies. The enhanced dissolution rates of budesonide were observed from SCF-treated budesonide-PEO mixtures. The amorphous characteristic of the budesonide, the better mixing of drug and PEO powders in the presence of SC CO₂, together with the improved wettability of the drug in PEO, produced a remarkable enhancement of the in vitro drug dissolution rate. Thus, budesonide-PEO solid dispersions with enhanced dissolution rate can be prepared using organic solvent-free SCF process.     

Nimodipine (NM) tablets with high dissolution containing NM solid dispersions prepared by hot-melt extrusion

Using a mixture of Eudragit EPO and polyvinylpyrrolidone/vinyl acetate copolymer (PVP/VA) (Kollidon VA64) as carriers, a nimodipine solid dispersion (NM-SD) was prepared by hot-melt extrusion (HME) to achieve high dissolution. The dissolution profiles in 900 mL 0.1 mol/L HCl showed that the drug release of NM-SD reached 90% in 1h. Powder X-ray diffraction (PXRD) and differential scanning calorimetry (DSC) were used to characterize the state of NM. The results obtained showed that NM was in an amorphous form in the solid dispersion (SD). NM-SD tablets (NM-T-SD) were compressed by wet granulation and direct compression, respectively. The stability of NM-T-SD was examined during a 2-month storage period (40 degrees C, RH 75%). The results showed that the dissolution of NM-T-SD was slightly reduced after 2 months storage (40 degrees C, RH 75%), which implied that aging occurred to some degree. However, no NM crystals could be observed by PXRD after 2 months storage for NM-T-SD (F11) prepared by direct compression.     

Biopharmaceutical Studies on Solid Dispersions of Nalidixic Acid in Modified Starches

The objective of the study is to improve the dissolution rate and efficiency and bioavailability of nalidixic acid (NA) and to evaluate three modified starches namely dextrin (D) β-cyclodextrin (β-CD) and hydroxyethyl starch (HES) as carriers for solid dispersions. Solid dispersions of NA in D, β-CD and HES were prepared by common solvent method and the dispersions were evaluated by TLC, IR, DTA, X-ray diffraction, moisture absorption, dissolution rate and bioavailability studies. The three modified starches were found to be non-hygroscopic, non-interacting carriers giving solid dispersions and effective in increasing the dissolution rate, efficiency and absorption rate of NA. A marked reduction in the crystallinity and crystal size of NA in the dispersions was observed.     

Biopharmaceutical Studies on Solid Dispersions of Nalidixic Acid in Modified Starches

Abstract

The objective of the study is to improve the dissolution rate and efficiency and bioavailability of nalidixic acid (NA) and to evaluate three modified starches namely dextrin (D) β-cyclodextrin (β-CD) and hydroxyethyl starch (HES) as carriers for solid dispersions. Solid dispersions of NA in D, β-CD and HES were prepared by common solvent method and the dispersions were evaluated by TLC, IR, DTA, X-ray diffraction, moisture absorption, dissolution rate and bioavailability studies. The three modified starches were found to be non-hygroscopic, non-interacting carriers giving solid dispersions and effective in increasing the dissolution rate, efficiency and absorption rate of NA. A marked reduction in the crystallinity and crystal size of NA in the dispersions was observed.     

Nimodipine (NM) tablets with high dissolution containing NM solid dispersions prepared by hot-melt extrusion

Using a mixture of Eudragit^® EPO and polyvinylpyrrolidone/vinyl acetate copolymer (PVP/VA) (Kollidon VA64) as carriers, a nimodipine solid dispersion (NM-SD) was prepared by hot-melt extrusion (HME) to achieve high dissolution. The dissolution profiles in 900?mL 0.1?mol/L HCl showed that the drug release of NM-SD reached 90% in 1?h. Powder X-ray diffraction (PXRD) and differential scanning calorimetry (DSC) were used to characterize the state of NM. The results obtained showed that NM was in an amorphous form in the solid dispersion (SD). NM-SD tablets (NM-T-SD) were compressed by wet granulation and direct compression, respectively. The stability of NM-T-SD was examined during a 2-month storage period (40°C, RH 75%). The results showed that the dissolution of NM-T-SD was slightly reduced after 2 months storage (40°C, RH 75%), which implied that aging occurred to some degree. However, no NM crystals could be observed by PXRD after 2 months storage for NM-T-SD (F₁₁) prepared by direct compression.     

Studies on solid dispersions of nifedipine

Nifedipine-Polyethylene glycol solid dispersions were prepared by melting or fusion method in order to improve nifedipine solubility in the aqueous body fluids. The dissolution rate of the drug was markedly increased in these solid dispersion systems. The increase in dissolution was a function of the ratio of drug to polyethylene glycol used and the molecular weight of polyethylene glycol. The dissolution rate was compared with a 10% w/w physical mixture of drug with polyethylene glycol.

The physical state of nifedipine after fusion was determined by X-ray crystallography on the pure drug and on the solidified melts. The X-ray diffraction studies indicated that nifedipine in the solid dispersion which was obtained by sudden cooling of the melt, was in the thermodynamically unstable metastable form. It was established that the slow cooling of the melt as well as powdering of solid dispersion resulted in the emergence of crystallinity.

The effect of aging on nifedipine-polyethylene glycol 6000 solid dispersions has been investigated. After storage at room temperature for six months, solid dispersions showed no change in the dissolution rate and the X-ray diffraction pattern showed slight enhancement in crystallinity.     

Studies on solid dispersions of nifedipine

Abstract

Nifedipine-Polyethylene glycol solid dispersions were prepared by melting or fusion method in order to improve nifedipine solubility in the aqueous body fluids. The dissolution rate of the drug was markedly increased in these solid dispersion systems. The increase in dissolution was a function of the ratio of drug to polyethylene glycol used and the molecular weight of polyethylene glycol. The dissolution rate was compared with a 10% w/w physical mixture of drug with polyethylene glycol.

The physical state of nifedipine after fusion was determined by X-ray crystallography on the pure drug and on the solidified melts. The X-ray diffraction studies indicated that nifedipine in the solid dispersion which was obtained by sudden cooling of the melt, was in the thermodynamically unstable metastable form. It was established that the slow cooling of the melt as well as powdering of solid dispersion resulted in the emergence of crystallinity.

The effect of aging on nifedipine-polyethylene glycol 6000 solid dispersions has been investigated. After storage at room temperature for six months, solid dispersions showed no change in the dissolution rate and the X-ray diffraction pattern showed slight enhancement in crystallinity.     

Carbamazepine and Polyethylene Glycol Solid Dispersions: Preparation,in Vitro Dissolution,and Characterization

Abstract

The objective of this study was to prepare solid dispersions of carbamazepine (CBZ) using polyethylene glycol (PEG) 4000 and PEG 6000, measure the dissolution, and characterize using x-ray diffraction, DSC, and IR spectroscopy. Solid dispersions were prepared by either the melt or solvent methods. A comparison of dissolution profiles of the solid dispersions indicated dramatic increases in the rate and extent of CBZ dissolution from solid dispersions. The dissolution of physical mixtures provided evidence of the solubilizing effects of PEGs. Untreated CBZ exhibited 10.09 ± 2.92% dissolution in 10 min (D_l0); whereas, a melt of PEG 6000 and CBZ at a ratio of 6: 1 provided 36.49 ± 1.97% and a melt of PEG 4000 and CBZ at a ratio of 6: 1 gave a D₁₀ of 23.59 ± 1.45%. The rate and extent of dissolution of CBZ were significantly higher when blends of the PEGs were employed to prepare solid dispersion. The melt method provided significantly higher rate and extent of dissolution of CBZ than the solvent method. Also, the rate and extent of dissolution of CBZ were significantly greater when the solid dispersion was cooled at room temperature as opposed to with ice (faster). X-ray diffractometry revealed almost a complete loss of crystallinity of CBZ in solid dispersions. IR spectrometry indicated an increase in amorphocity of the PEGs after melting. IR spectra suggested that no complexation occurred between the PEGs and CBZ. Alterations in the crystallinity of the system were also supported by the DSC thermograms. Decreasing heats of fusion implied decrease in crystallinity, which would be expected to provide greater dissolution rates. Peak melting temperatures obtained from the thermograms ruled out the possibility of the formation of a eutectic mixture. However, the formation of solid solution could also be a possible mechanism for the increase in dissolution.     

Carbamazepine and Polyethylene Glycol Solid Dispersions: Preparation, in Vitro Dissolution, and Characterization

The objective of this study was to prepare solid dispersions of carbamazepine (CBZ) using polyethylene glycol (PEG) 4000 and PEG 6000, measure the dissolution, and characterize using x-ray diffraction, DSC, and IR spectroscopy. Solid dispersions were prepared by either the melt or solvent methods. A comparison of dissolution profiles of the solid dispersions indicated dramatic increases in the rate and extent of CBZ dissolution from solid dispersions. The dissolution of physical mixtures provided evidence of the solubilizing effects of PEGs. Untreated CBZ exhibited 10.09 ± 2.92% dissolution in 10 min (D_l0); whereas, a melt of PEG 6000 and CBZ at a ratio of 6: 1 provided 36.49 ± 1.97% and a melt of PEG 4000 and CBZ at a ratio of 6: 1 gave a D₁₀ of 23.59 ± 1.45%. The rate and extent of dissolution of CBZ were significantly higher when blends of the PEGs were employed to prepare solid dispersion. The melt method provided significantly higher rate and extent of dissolution of CBZ than the solvent method. Also, the rate and extent of dissolution of CBZ were significantly greater when the solid dispersion was cooled at room temperature as opposed to with ice (faster). X-ray diffractometry revealed almost a complete loss of crystallinity of CBZ in solid dispersions. IR spectrometry indicated an increase in amorphocity of the PEGs after melting. IR spectra suggested that no complexation occurred between the PEGs and CBZ. Alterations in the crystallinity of the system were also supported by the DSC thermograms. Decreasing heats of fusion implied decrease in crystallinity, which would be expected to provide greater dissolution rates. Peak melting temperatures obtained from the thermograms ruled out the possibility of the formation of a eutectic mixture. However, the formation of solid solution could also be a possible mechanism for the increase in dissolution.     

Supercritical antisolvent versus coevaporation: preparation and characterization of solid dispersions

The objective of this work was to improve the dissolution rate and aqueous solubility of oxeglitazar. Solid dispersions of oxeglitazar in PVP K17 (polyvinilpyrrolidone) and poloxamer 407 (polyoxyethylene-polyoxypropylene block copolymer) were prepared by supercritical antisolvent (SAS) and coevaporation (CoE) methods. Drug-carrier formulations were characterized by powder X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, gas chromatography, UV/VIS spectroscopy and in vitro dissolution tests. The highest dissolution rate (nearly 3-fold higher than raw drug) was achieved by preparation of drug/PVP K17 coevaporate. Oxeglitazar/PVP K17 solid dispersions were stabilized by hydrogen bonding but contained higher amount of residual dichloromethane (DCM) than poloxamer 407 formulations regardless of the method of preparation. SAS prepared oxeglitazar/poloxamer 407 dissolved more than two times faster than raw drug. However, unlike PVP K17, poloxamer 407 did not form a single phase amorphous solid solution with oxeglitazar which has been manifested in higher degrees of crystallinity, too. Among the two techniques, evaluated in this work, conventional coevaporation resulted in higher amorphous content but SAS reduced residual solvent content more efficiently.     

Supercritical Antisolvent Versus Coevaporation— Preparation and Characterization of Solid Dispersions

The objective of this work was to improve the dissolution rate and aqueous solubility of oxeglitazar. Solid dispersions of oxeglitazar in PVP K17 (polyvinilpyrrolidone) and poloxamer 407 (polyoxyethylene-polyoxypropylene block copolymer) were prepared by supercritical antisolvent (SAS) and coevaporation (CoE) methods. Drug-carrier formulations were characterized by powder X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, gas chromatography, UV/VIS spectroscopy and in vitro dissolution tests. The highest dissolution rate (nearly 3-fold higher than raw drug) was achieved by preparation of drug/PVP K17 coevaporate. Oxeglitazar/PVP K17 solid dispersions were stabilized by hydrogen bonding but contained higher amount of residual dichloromethane (DCM) than poloxamer 407 formulations regardless of the method of preparation. SAS prepared oxeglitazar/poloxamer 407 dissolved more than two times faster than raw drug. However, unlike PVP K17, poloxamer 407 did not form a single phase amorphous solid solution with oxeglitazar which has been manifested in higher degrees of crystallinity, too. Among the two techniques, evaluated in this work, conventional coevaporation resulted in higher amorphous content but SAS reduced residual solvent content more efficiently.     

Drug–polymer miscibility,interactions, and precipitation inhibition studies for the development of amorphous solid dispersions for the poorly soluble anticancer drug flutamide

The major goal of this research was to successfully formulate solid dispersion (SD) of the poorly soluble anticancer drug flutamide (FLT) using various hydrophilic polymers. Furthermore, to get more insight into SD, solid-state studies (miscibility and molecular interaction) were correlated with solution study (precipitation inhibition, dissolution). Hydrophilic polymers like PVP K90, HPMC, Eudragit EPO, and PEG 8000 were used at different drug-to-polymer w/w ratios. Solid-state miscibility studies were carried out using modulated differential scanning calorimetry (MDSC). SDs were prepared using solvent-evaporation technique and characterized by powder X-ray diffraction (PXRD) and MDSC. Infrared, Raman spectroscopy and molecular modeling were used to investigate drug-polymer interactions in the dispersions. Precipitation inhibition studies were carried out at various FLT-hydrophilic polymer ratios. Precipitation inhibition studies showed that PEG 8000 has the highest efficiency, followed by PVP K90, while HPMC and EPO showed no effect on precipitation inhibition. In the solid-state, MDSC of the physical mixture (PM) suggested that FLT is miscible to a greater extent with EPO and PEG 8000. Characterization of the amorphous dispersions using MDSC and PXRD concluded that FLT transformed from crystalline to amorphous form in the presence of PVP K90 and PEG 8000. Spectroscopic results confirmed stronger interaction of FLT with PVP K90 and PEG 8000, thereby confirming the in-solution precipitation and molecular modeling binding energy results. Amorphous dispersions formulated with PVP and PEG were stable and showed higher dissolution, an important property necessary to improve the physicochemical properties and drug delivery of poorly soluble anticancer drug FLT.     

Dissolution, Bioavailability and Ulcerogenic Studies on Solid Dispersions of Indomethacin in Water Soluble Cellulose Polymers

The dissolution rate, bioavailability and ulcerogenic activity of indomethacin dispersed in water soluble cellulose polymers was investigated. Solid dispersions of indomethacin in hydroxypropyl cellulose-SL (HPC-SL), hydroxypropylmethyl cellulose (HPMC) and hydroxyethyl cellulose (HEC) were prepared by common solvent method with a view to improve its dissolution and absorption characteristics. The dispersions were evaluated by X-ray diffraction, TLC, IR, dissolution rate, bioavailability and ulcerogenic studies. TLC and IR studies indicated no interaction between indomethacin and carriers. Indomethacin in the dispersions was found to be in amorphous form. Marked increase in the dissolution rate and efficiency of indomethacin was observed in the case of solid dispersions. HPC-SL gave the highest dissolution improvement. A 30-fold increase in dissolution was observed with indomethacin-HPC-SL (9:1) dispersion.

In vivo studies in human subjects showed a significant increase in absorption rate (k_a) and serum levels of indomethacin with solid dispersions when compared to indomethacin alone. However, the extent of bioavailabilty was the same with both indomethacin and its solid dispersions. About 70-80 per cent reduction in ulcerogenic activity was observed with solid dispersions and the dispersions were found to have negligible ulcerogenic activity.     

Chemometric Modelling of Dissolution Rates of Griseofulvin From Solid Dispersions With Polymers

The quantitative relationship between the release rate of griseofulvin and the chemical and physical properties of a series of polymers, used for the preparations of solid dispersions, was investigated by the application of multiple regression analysis (MRA), partial least square analysis (PLS) and a new non linear chemometric procedure called CARSO (Computer Aided Response Surface Optimization).

It was confirmed that the degree of crystallinity of griseofulvin and the wettability of the powder samples are important in the dissolution mechanism and in the prediction of dissolution profiles of griseofulvin from these solid dispersions.     

Preparation of amorphous solid dispersions by rotary evaporation and KinetiSol Dispersing: approaches to enhance solubility of a poorly water-soluble gum extract

Acetyl-11-keto-β-boswellic acid (AKBA), a gum resin extract, possesses poor water-solubility that limits bioavailability and a high melting point making it difficult to successfully process into solid dispersions by fusion methods. The purpose of this study was to investigate solvent and thermal processing techniques for the preparation of amorphous solid dispersions (ASDs) exhibiting enhanced solubility, dissolution rates and bioavailability. Solid dispersions were successfully produced by rotary evaporation (RE) and KinetiSol® Dispersing (KSD). Solid state and chemical characterization revealed that ASD with good potency and purity were produced by both RE and KSD. Results of the RE studies demonstrated that AQOAT®-LF, AQOAT®-MF, Eudragit® L100-55 and Soluplus with the incorporation of dioctyl sulfosuccinate sodium provided substantial solubility enhancement. Non-sink dissolution analysis showed enhanced dissolution properties for KSD-processed solid dispersions in comparison to RE-processed solid dispersions. Variances in release performance were identified when different particle size fractions of KSD samples were analyzed. Selected RE samples varying in particle surface morphologies were placed under storage and exhibited crystalline growth following solid-state stability analysis at 12 months in comparison to stored KSD samples confirming amorphous instability for RE products. In vivo analysis of KSD-processed solid dispersions revealed significantly enhanced AKBA absorption in comparison to the neat, active substance.     

Physical Characterization and Dissolution Properties of Verapamil. HCI Coprecipitates

Verapamil hydrochloride coprecipitates were prepared using solvent-evaporation technique. Ethylcellulose, hydroxypropyl cellulose, hydroxypropyl methylcellulose phtalate HP 55 were used as polymers. The solid dispersions obtained were grounded and sieved to prepare solid dispersion granules. The dissolution behavior of solid dispersion granules was studied using buffer solutions with pH 1.5; 6.8 and half-change method during 24 hours. The drug release rate was found to be dependent on the ratio of the polymers in coprecipitates. In order to understand the drug release mechanism better, the release data were tested assuming common kinetic models. The best fit kinetic model was diffusion model and the dissolution rate constants calculated using Higuchi equation, demonstrated that dissolution rate increased with increasing the ratio of HPMCP HP 55 in coprecipitates. Physical characterization was made using X-ray diffractometry, IR spectrophotometry and DTA studies. Prepared coprecipitates were X-ray amorphous. Also, after nine months real time studies they remain amorphous, with no changes in their IR spectra and DTA curves. The dissolution rate of the test dispersions showed no significant changes during the stability studies, reflecting the stability of X-ray amorphous drug phase.