Effect of solid state transition on the physical stability of suspensions containing bupivacaine lipid microparticles

Bupivacaine lipid microparticles were prepared and evaluated as a parenteral sustained-release dosage form for postoperative pain management. Bupivacaine free base was incorporated into a molten tristearin matrix and lipid micro-particles were subsequently formed from this molten mixture by a spray-congealing process. A 3% injectable bupivacaine lipid microparticle suspension was prepared by dispersing 30% bupivacaine lipid microparticles in an aqueous medium containing carboxymethylcellulose (CMC), mannitol, and Tween 80. Upon room temperature storage, the fluid suspension gradually changed into a nonflowing semisolid (gelation) as a result of crystal growth of bupivacaine. However, suspensions prepared with bupivacaine lipid microparticles that were previously annealed at an elevated temperature remained fluid upon long-term storage. Differential scanning calorimetry (DSC), x-ray powder diffraction (XRPD), and isoperibol solution calorimetry were used to investigate the changes in the solid-state properties of tristearin and bupivacaine in the lipid microparticles before and after the heat treatment. The DSC and XRPD results indicate that after 24 hours of heating at 40 degrees C, tristearin was completely converted from the unstable alpha form to the stable beta form. Using the isoperibol solution calorimetric method, bupivacaine was found to transform into a more stable form after the lipid microparticles were heated at 60 degrees C for 24 hours. The generation of the unstable solid forms of tristearin and bupivacaine was attributed to the resolidification of both components from the molten mixture during the spray-congealing process.     

Layered lipid microcapsules for mesalazine delayed-release in children

The goal was to make available a delayed-release dosage form of mesalazine to be dispersed in water to facilitate swallowing in adults and children. Mesalazine microparticles containing carnauba wax were prepared by spray-congealing technique. A second step of spray-congealing of carnauba microparticles dispersed in liquefied stearic acid gave rise to mesalazine lipid microcapsules in which several carnauba microparticles remained embedded as cores in a reservoir structure. In order to favor their water dispersion, the lipid microcapsules were dry coated by tumbling them with different ratios of mannitol/lecithin microparticles prepared by spray-drying. Release rate measurements showed a delayed-release behavior, in particular a pH-dependence with less than 10% of drug released in acidic medium and complete release in phosphate buffer pH 7.4 in 4-5h. The layering with hydrophilic excipient microparticles allowed manufacturing of a pH-dependent dosage form suitable for extemporaneous oral use in adults and children.     

Enhancement of melatonin photostability by encapsulation in lipospheres

The effect of lipid microparticle carrier systems on the light-induced degradation of melatonin was investigated. Microspheres loaded with melatonin were prepared using tristearin or tripalmitin as the lipid material and hydrogenated phosphatidylcholine or polysorbate 60 as the emulsifier. The obtained lipid microspheres were characterized by scanning-electron microscopy and differential scanning calorimetry. Free or microencapsulated melatonin was incorporated in a model cream formulation (oil-in-water emulsion) and irradiated with a solar simulator. The extent of photodegradation was measured by high-performance liquid chromatography. The photolysis experiments demonstrated that the light-induced decomposition of melatonin was markedly decreased by encapsulation into lipid microspheres based on tristearin and phosphatidylcholine (the extent of degradation was 19.6% for unencapsulated melatonin compared to 5.6% for the melatonin-loaded microparticles). Therefore, incorporation in lipid microparticles can be considered an effective system to enhance the photostability of melatonin.     

Palatable reconstitutable dry suspension of artemether for flexible pediatric dosing using cyclodextrin inclusion complexation

The present research was conducted to investigate the inclusion complexation of artemether (ARM) with beta-cyclodextrin (CD) with the aim of masking the bitterness along with improving the drug release and preparing a stable palatable formulation of ARM especially for pediatrics. A physical mixture and kneaded system were prepared to study the inclusion complexation. Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), X-ray powder diffraction (XRPD) and scanning electron microscopy (SEM) were performed to identify the physicochemical interaction between drug and carrier, hence its effect on drug release. Reconstitutable dry suspension was evaluated for angle of repose, sedimentation characterization and pH. In vitro drug release studies for physical mixture and kneaded system were performed at pH, 1.2 and 6.8. Bitterness score was evaluated using gustatory sensation test. The FTIR, DSC and XRPD studies indicated inclusion complexation in physical mixture and kneaded system. In addition, physical mixture and kneaded system exhibited improved drug release at pH, 1.2 and 6.8. To formulate palatable reconstitutable dry suspension of ARM, the 1:20M physical mixture was selected based on bitterness score. Reconstitutable dry suspension prepared using physical mixture (DS4), showed complete bitter taste masking, good flowability and ease of redispersibility. Taste evaluation of reconstitutable dry suspension in human volunteers rated tasteless with a score of 0 to DS4 and 3 to DS5 (reconstitutable dry suspension prepared using pure ARM). This conclusively demonstrated a stable and palatable reconstitutable dry suspension of ARM using CD inclusion complexation for flexible pediatric dosing.     

Palatable reconstitutable dry suspension of artemether for flexible pediatric dosing using cyclodextrin inclusion complexation

The present research was conducted to investigate the inclusion complexation of artemether (ARM) with beta-cyclodextrin (CD) with the aim of masking the bitterness along with improving the drug release and preparing a stable palatable formulation of ARM especially for pediatrics. A physical mixture and kneaded system were prepared to study the inclusion complexation. Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), X-ray powder diffraction (XRPD) and scanning electron microscopy (SEM) were performed to identify the physicochemical interaction between drug and carrier, hence its effect on drug release. Reconstitutable dry suspension was evaluated for angle of repose, sedimentation characterization and pH. In vitro drug release studies for physical mixture and kneaded system were performed at pH, 1.2 and 6.8. Bitterness score was evaluated using gustatory sensation test. The FTIR, DSC and XRPD studies indicated inclusion complexation in physical mixture and kneaded system. In addition, physical mixture and kneaded system exhibited improved drug release at pH, 1.2 and 6.8. To formulate palatable reconstitutable dry suspension of ARM, the 1:20M physical mixture was selected based on bitterness score. Reconstitutable dry suspension prepared using physical mixture (DS4), showed complete bitter taste masking, good flowability and ease of redispersibility. Taste evaluation of reconstitutable dry suspension in human volunteers rated tasteless with a score of 0 to DS4 and 3 to DS5 (reconstitutable dry suspension prepared using pure ARM). This conclusively demonstrated a stable and palatable reconstitutable dry suspension of ARM using CD inclusion complexation for flexible pediatric dosing.     

In vitro characterization of polyorthoester microparticles containing bupivacaine

Laboratory-scale spray-congealing equipment was utilized to fabricate injectable microparticles consisting of polyorthoester and bupivacaine. Operating conditions for the spray-congealing process were optimized to produce microparticles with the desired shape and particle size to yield acceptable syringeability and injectability. Characterizations were performed to determine the chemico-physical properties of polyorthoester before and after microparticle fabrication. Microparticles with different drug loadings and comparable particle sizes were produced, and their in vitro drug-release profiles were determined. The in vitro drug release of microparticles with a high drug loading was markedly faster than those with a low drug loading. This is partially attributed to a more significant initial burst-drug release of the microparticles with a high drug loading. The microparticles have demonstrated the potential to be used for long-acting postsurgery pain management by local injection.     

Enhanced Release of Indomethacin from PVP/Stearic Acid Microcapsules Prepared Coupling Co-freeze-drying and Ultrasound Assisted Spray-congealing Process

Purpose Fast releasing indomethacin microparticles were prepared encapsulating co-freeze-dried indomethacin/poly(vinylpyrrolidone) particles (IMC/PVP) into molten stearic acid (SA), by means of a ultrasonic spray-congealing technique. Materials and Methods IMC particles were suspended in a PVP aqueous solution and the system was then freeze-dried. A suspension was prepared from the co-freeze dried IMC/PVP powder into molten SA that was then atomized into small droplets using ultrasound. Solidification in air produced microparticles having regular macroscopic morphology and coated by a SA thin external film. At each step the material was examined by electron microscopy (SEM and EDAX), thermal analysis and dissolution tests. Results SEM examination did not reveal a smooth surface, differently from what was observed in the case of pure SA microparticles, obtained by the same method. The external film was found to uniformly protect the internal core of the capsules: EDAX spectra demonstrated the absence of the IMC identifying Cl peak on the surface, when the spectra were carried out at low energy of the electron beam. HPLC analysis verified that the drug was uniformly distributed inside the final microparticles at all the size fractions considered. Thermal microscopy confirmed the presence of IMC crystals, after the fusion of the external SA coat. Conclusions The behavior of microparticles to dissolution at pH 7.4 was superior to that of pure drug, reaching 70% of the drug released, after 20 min. Finally the system examined is stable towards aging: no difference in the dissolution behavior could be detected for the final microparticles after 8 months at 25°C.     

Raman and thermal analysis of indomethacin/PVP solid dispersion enteric microparticles

Indomethacin (IMC) and three types of poly-(vinylpyrrolidone) (PVP 12PF, PVP K30 and PVP K90) were studied in the form of solid dispersion, prepared with the solvent evaporation method, by spectroscopic (Raman, FT-IR, X-ray diffraction), thermal (differential scanning calorimetry, thermogravimetry, hot-stage microscopy), fractal and image analysis. Raman and FT-IR micro-spectroscopy indicated the occurrence of drug/polymer interaction and the presence of an amorphous form of IMC, as also resulting from X-ray diffractometry. Hot-stage microscopy suggested that the interaction between IMC and the polymer occurring on heating of a physical mixture, is common to other acidic compounds and causes a depression of the temperature of the appearance of a molten phase. Co-evaporated particles were coated by spray-congealing process with molten stearic acid for gastroprotection, but also for stabilization of the amorphous structure of the drug: the final particles were spherically shaped. Dissolution tests carried out on the final microparticles showed that the coating with stearic acid prevents IMC release at acidic pH and also protects against recovery of the IMC crystallinity, at least after 9 months of aging: the extent and mode of the release, before and after aging, overlap perfectly. The test revealed a notable improvement of the drug release rate from the solid dispersion at suitable pH, with respect to pure IMC. The comparison of the present solid dispersion with IMC/PVP (surface) solid dispersion obtained by freeze-drying of an aqueous suspension, where IMC maintained its crystalline state, revealed that there was no difference concerning the release rate, but suggested a superior quality of this last process as a mean of improving IMC availability for the easiness of preparation and stability, due to the absence of the amorphous state of the drug, as a possible instability source of the system. Finally, the coating with stearic acid is discussed as a determining process for the practical application of solid dispersions.     

Spray congealed lipid microparticles with high protein loading: preparation and solid state characterisation

The spray-congealing technique, a solvent-free drug encapsulation process, was successfully employed to obtain lipid-based particulate systems with high (10-20% w/w) protein loading. Bovine serum albumin (BSA) was utilised as model protein and three low melting lipids (glyceryl palmitostearate, trimirystin and tristearin) were employed as carriers. BSA-loaded lipid microparticles were characterised in terms of particle size, morphology and drug loading. The results showed that the microparticles exhibited a spherical shape, mean diameter in the range 150-300 μm and an encapsulation efficiency higher than 90%. Possible changes in the protein structure as a result of the manufacturing process was then investigated for the first time using UV spectrophotometry in fourth derivative mode and FT-Raman spectroscopy. The results suggested that the structural integrity of the protein was maintained within the particles. Thermal analysis indicated that the effect of protein on the thermal properties of the carriers could be detected. Spray-congealing could thus be considered a suitable technique to produce highly BSA-loaded microparticles preserving the structure of the protein.     

Polymorphic form of piroxicam influences the performance of amorphous material prepared by ball-milling

The objective of this study was to investigate the influence of the starting solid state form of piroxicam (anhydrate form I: PRXAH I vs form II: PRXAH II) on the properties of the resulting amorphous material. The second objective was to obtain further insight into the impact of critical factors like thermal stress, dissolution medium and storage conditions on the thermal behavior, solid state transformations and physical stability of amorphous materials. For analysis differential scanning calorimetry (DSC), Raman spectroscopy and X-ray powder diffractometry (XRPD) were used. Pair-wise distribution function (PDF) analysis of the XRPD data was performed. PDF analysis indicated that the recrystallization behavior of amorphous samples was influenced by the amount of residual order in the samples. The recrystallization behavior of amorphous samples prepared from PRXAH I showed similarity to the starting material, whereas the recrystallization behavior of amorphous samples prepared from PRXAH II resembled to that of the PRX form III (PRXAH III). Multivariate data analysis (MVDA) helped to identify that the influence of storage time and temperature was more pronounced in the case of amorphous PRX prepared from PRXAH I. Furthermore, the wet slurry experiments with amorphous materials revealed the recrystallization of amorphous material as PRXMH in the biorelevant medium.     

Nanocrystals as tool to improve piroxicam dissolution rate in novel orally disintegrating tablets

In this paper, orally disintegrating tablets (ODT) were prepared using nanocrystal formulations in order to optimise dissolution properties of lipophilic, poorly soluble drug piroxicam (PRX). Different nanocrystal formulations were prepared using a high pressure homogenisation technique and poloxamer 188 as stabiliser. Characterisation of PRX nanocrystal ODT was carried out by infrared spectroscopy (FTIR), X-ray powder diffractometry (XRPD), differential scanning calorimetry and photon correlation spectroscopy. Dissolution study of PRX ODT was performed in distilled water (pH 5.5) and was compared to that of PRX coarse suspension ODT, PRX/poloxamer 188 physical mixture and bulk PRX samples. The XRPD and FTIR studies demonstrated that the homogenisation process led to a polymorphic transition from form I (bulk commercial PRX) to form III and monohydrate form of the nanocrystals. All ODT formulations prepared using PRX nanosuspensions showed a higher PRX dissolution rate compared with the ODT prepared with the coarse PRX. Since the solubility of the different PRX polymorphic forms increased only slightly from bulk PRX (form I) to monohydrate, form II and form III, we can conclude that the improvement in PRX dissolution rate is mainly caused by the increased surface-to-volume ratio due to the submicron dimension of the drug particles.     

托伐普坦固体分散体的制备及体外溶出特性考察

目的 采用固体分散技术提高难溶性药物托伐普坦的体外溶出度。方法 选用聚维酮K_29/32为载体材料,以溶剂蒸发法制备托伐普坦固体分散体。采用差示扫描量热法(DSC)、X-射线粉末衍射法(XRPD)对所得固体分散体进行鉴定, 并进行溶解度、体外溶出实验。结果 固体分散体的DSC 图谱及X-射线粉末衍射确定了托伐普坦以无定形态分散在载体中, 体外溶解实验表明其溶出较原料药、物理混合物均有明显提高。结论 将托伐普坦与PVP K_29/32制成固体分散体,其分散状态发生了改变,溶出性能明显提高。     

熔融法制备卡马西平-烟酰胺共结晶固体分散体

目的联用共结晶和固体分散技术,提高卡马西平的体外溶出度。方法以PVP VA64为载体,采用熔融法制备卡马西平-烟酰胺共结晶固体分散体。进行体外溶出实验,并采用粉末X射线衍射和差示扫描量热法鉴别卡马西平和烟酰胺在载体中的分散状态。结果卡马西平和烟酰胺结合形成共结晶后以无定形态或分子态分散在载体中,而在卡马西平固体分散体中,药物和载体形成低共融物,以微晶状态分散。卡马西平-烟酰胺共结晶固体分散体的体外溶出结果优于卡马西平固体分散体。结论共结晶固体分散体显著提高了药物的体外溶出度。     

Understanding the solid-state behaviour of triglyceride solid lipid extrudates and its influence on dissolution

Three monoacid triglycerides differing in their fatty acid chain lengths were extruded below their melting temperatures. Physical characterization was conducted on the powders as well as the extrudates with a combination of DSC, XRPD and vibrational spectroscopy to get a deeper insight into the complex solid-state behaviour of lipids and solid lipid extrudates during processing and storage. The combination of extrusion temperature and friction was a key factor for the lipid polymorphic behaviour after extrusion. Polymorphic transitions had a strong influence on the dissolution behaviour due to crystallization of the stable β-form from the unstable α-form on the surface of the extrudate. These correlations help to understand the solid-state behaviour of lipids and to avoid process conditions which lead to unstable dosage forms. Tailor-made dissolution profiles for a model drug could be achieved using triglycerides of different fatty acid chain lengths as the dissolution rate is chain-length dependent. The solid-state form of the drug was unchanged after storage in accelerated conditions over 10 months. These studies demonstrate that although triglycerides are a promising basis for oral dosage forms, a good understanding and monitoring of the solid-state behaviour is mandatory to obtain reliable and reproducible dosage forms.     

Loading of tacrolimus containing lipid based drug delivery systems into mesoporous silica for extended release

Many studies had been focused on designing tacrolimus sustained release preparations based on solid dispersion technique, but no one had tried to employ mesoporous silica as the carrier material to realize this goal. The purpose of this study was to develop a novel, simple and environmental friendly drug loading method with mesoporous silica to obtain tacrolimus sustained-release preparation. Tacrolimus was firstly dissolved in the molten mixed lipid composed of Compritol 888 ATO and Gelucire 50/13 to prepare a drug loaded lipid-based drug delivery systems (LBDDS), then the liquid LBDDS was adsorbed by mesoporous silica to transfer the liquid into solid powder, ie. the tacrolimus sustained release silica-lipid hybrid (SLH). The SLH was characterized by SEM, CLSM, XRPD and DSC, and the in vitro drug release was tested using a paddle method. SEM and CLSM observation showed that the LBDDS was efficiently distributed throughout the pores of the silica. The results of DSC and XRPD illustrated that the lipid existed inside the silica at amorphous state. The drug-loaded SLH showed good flowability, compressibility, compactibilty and two-phase in vitro drug release process within 24 hours, which did not change obviously even after storage at 40 °C for 10 d. The present study provided a novel and simple method to prepare tacrolimus sustained release powder, which provided a feasible solution to solidify the liquid LBDDS of not only extended drug release behavior, but also improved stability and micromeritic properties.     

Encapsulation in lipospheres of the complex between butyl methoxydibenzoylmethane and hydroxypropyl-beta-cyclodextrin

The aim of this study was to investigate the incorporation into lipospheres of the complex between hydroxypropyl-β-cyclodextrin (HP-β-CD) and the sunscreen agent, butyl methoxydibenzoylmethane (BMDBM) and to examine the influence of this system on the sunscreen photostability. The formation of the inclusion complex was confirmed by thermal analysis and powder X-ray diffraction. Lipid microparticles loaded with free BMDBM or its complex with HP-β-CD were prepared using tristearin as the lipid material and hydrogenated phosphatidylcholine as the emulsifier. The obtained lipospheres were characterized by scanning electron microscopy and differential scanning calorimetry. The microparticle size (15–40 μm) was not affected by the presence of the complex. Release of BMDBM from the lipospheres was lower when it was incorporated as inclusion complex rather than as free molecule. Unencapsulated BMDBM, its complex with HP-β-CD, the sunscreen-loaded lipospheres or the lipoparticles containing the BMDBM/HP-β-CD complex, were introduced into a model cream (oil-in-water emulsion) and irradiated with a solar simulator. The photodegradation studies showed that all the examined systems achieved a significant reduction of the light-induced decomposition of the free sunscreen agent (the BMDBM loss decreased from 28.9 to 17.3–15.2%). However, photolysis experiments performed during 3 months storage of the formulations, demonstrated that the photoprotective properties of the HP-β-CD complex and of BMDBM alone-loaded lipospheres decreased over time, whereas the microencapsulated HP-β-CD/BMDBM complex retained its photostabilization efficacy. Therefore, incorporation in lipid microparticles of BMDBM in the cyclodextrin complex form is more effective in enhancing the sunscreen photostability than the complex alone or the liposphere-entrapped free BMDBM.     

Formulation and characterization of bupivacaine lipospheres

Bupivacaine lipospheres were prepared as a parenteral sustained-release system for post-operative pain management. Bupivacaine free base was incorporated into micron-sized triglyceride solid particles coated with phospholipids, which were formed via a hot emulsification and cold resolidification process. The bupivacaine liposphere dispersions were characterized with respect to drug loading, particle-size distribution, and morphology. Gelation of the fluid liposphere dispersions was observed at different time intervals upon storage. The type of phospholipids used in the formulation was found to have a major impact on the gelation of the dispersion. The use of synthetic phospholipids instead of the natural phospholipids in the formulation yielded bupivacaine liposphere dispersions exhibiting prolonged gelation time. The addition of a hydrophilic cellulosic polymer can further improve the physical stability of the dispersion.     

Formulating Inhalable Dry Powders Using Two-Fluid and Three-Fluid Nozzle Spray Drying

Purpose

The spray drying process is widely applied for pharmaceutical particle engineering. The purpose of this study was to investigate advantages and disadvantages of two-fluid nozzle and three-fluid nozzle spray drying processes to formulate inhalable dry powders.

Methods

Budesonide nanocomposite microparticles (BNMs) were prepared by co-spray drying of budesonide nanocrystals suspended in an aqueous mannitol solution by using a two-fluid nozzle spray drying process. Budesonide-mannitol microparticles (BMMs) were prepared by concomitant spray drying of a budesonide solution and an aqueous mannitol solution using a spray drier equipped with a three-fluid nozzle. The resulting dry powders were characterized by using X-ray powder diffraction (XRPD), differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA) and Raman microscopy. A Next Generation Impactor was used to evaluate the aerodynamic performance of the dry powders.

Results

XRPD and DMA results showed that budesonide remained crystalline in the BNMs, whereas budesonide was amorphous in the BMMs. Spray drying of mannitol into microparticles resulted in a crystalline transformation of mannitol, evident from XRPD, DSC and Raman spectroscopy analyses. Both BMMs and BNMs displayed a faster dissolution rate than bulk budesonide. The yield of BNMs was higher than that of BMMs. The mass ratio between budesonide and mannitol was preserved in the BNMs, whereas the mass ratio in the BMMs was higher than the theoretical ratio.

Conclusions

Spray drying is an enabling technique for preparation of budesonide amorphous solid dispersions and nanocrystal-embedded microparticles. Two-fluid nozzle spray drying is superior to three-fluid nozzle spray drying in terms of yield.

     

Preparation and characterization of nitrendipine solid lipid nanoparticles

Nitrendipine, a dihydropyridine calcium channel blocker, has very poor oral bioavailability (10-20%) due to first pass effect. Solid lipid nanoparticle (SLN) delivery systems of nitrendipine have been developed using various triglycerides (trimyristin, tripalmitin and tristearin), soy phosphatidylcholine 95%, poloxamer 188 and charge modifiers stearylamine and dicetyl phosphate. SLNs were prepared by hot homogenization of melted lipids and aqueous phase followed by ultrasonication at temperatures above the melting point of lipids. Optimization studies of process and formulation variables were carried out. Particle size and zeta potential were measured by photon correlation spectroscopy (PCS) using Malvern zetasizer. Differential scanning calorimetry (DSC) and powder X-ray diffraction (PXRD) studies were performed to characterize state of drug and lipid modification. In vitro release studies were performed in phosphate buffer pH 6.8 using modified Franz diffusion cell. Stable nitrendipine SLNs of mean size range 79 to 213 nm and zeta potential -38.2 to +34.6 mV were developed. About 99% nitrendipine was entrapped in SLNs and were stable on storage at 4 and 25 degrees C. DSC and PXRD analyses revealed that nitrendipine is dispersed in SLNs in an amorphous state. The release pattern of drug is analyzed and found to follow Weibull distribution rather than first order and Higuchi equation.     

Polymorphic properties of micronized carbamazepine produced by RESS

Carbamazepine microparticles were produced by the rapid expansion of supercritical carbon dioxide solutions (RESS) method. The characteristics of the resulting particles were studied by X-ray powder diffraction (XRPD), differential scanning calorimetry (DSC), scanning electron microscopy (SEM) and image analysis. X-ray diffractograms and SEM photomicrographs revealed that the crystalline nature of the produced carbamazepine microparticles depended on operating pressure and temperature conditions. Different polymorphs were obtained under various operating conditions. Under certain temperature (below 40 degrees C) and pressure (below 240 bar) conditions, it was possible to form primarily the carbamazepine polymorph stipulated by US Pharmacopeia. A significant reduction was observed in the particle size and size distribution range of carbamazepine produced by RESS. The processed particles had a mean diameter smaller than 3 microm and a size distribution range between 0.5 and 2.5 microm compared to unprocessed starting material with a mean diameter of approximately 85 microm and a size distribution range between 15 and 336 microm. Thus, this study demonstrates that the polymorphic characteristics of carbamazepine microparticles produced by the RESS method can be controlled by varying operating pressure and temperature parameters.