The preparation and characterization of solid dispersions on pellets using a fluidized-bed system

Delivery of curcumin in a carboxymethyl cellulose and hydroxypropyl methyl cellulose carrier: Physicochemical properties and biological activity

Curcumin solid dispersions (Cur SDs) were prepared using hydroxypropyl methyl cellulose (HPMC) and sodium carboxymethyl cellulose (CMC) at different dosages. The results of Fourier transform infrared spectroscopy and Raman spectroscopy showed that the characteristic peak of curcumin shifted, and the addition of CMC enhanced this phenomenon. The addition of CMC reduced the contact angle, increased the surface free energy, and improved the solubility of Cur SDs. These changes were positively correlated with the amount of CMC. The surface morphology of Cur SDs changed from needle-like to sheet-like as observed by scanning electron microscopy. Cur SDs prepared by CMC and HPMC retained good biological activity. HT-29 human colon cancer cell analysis showed that the addition of CMC significantly improved the anti-proliferation effect of Cur SDs, thus enhancing the bioavailability of curcumin. Solid dispersions made with CMC and HPMC will be a promising hydrocolloid carrier to improve oral bioavailability and efficacy of curcumin.

Amorphous Solid Dispersions Layered onto Pellets—An Alternative to Spray Drying?

Spray drying is one of the most frequently used solvent-based processes for manufacturing amorphous solid dispersions (ASDs). However, the resulting fine powders usually require further downstream processing when intended for solid oral dosage forms. In this study, we compare properties and performance of spray-dried ASDs with ASDs coated onto neutral starter pellets in mini-scale. We successfully prepared binary ASDs with a drug load of 20% Ketoconazole (KCZ) or Loratadine (LRD) as weakly basic model drugs and hydroxypropyl-methyl-cellulose acetate succinate or methacrylic acid ethacrylate copolymer as pH-dependent soluble polymers. All KCZ/ and LRD/polymer mixtures formed single-phased ASDs, as indicated by differential scanning calorimetry, X-ray powder diffraction and infrared spectroscopy. All ASDs showed physical stability for 6 months at 25 °C/65% rH and 40 °C/0% rH. Normalized to their initial surface area available to the dissolution medium, all ASDs showed a linear relationship of surface area and solubility enhancement, both in terms of supersaturation of solubility and initial dissolution rate, regardless of the manufacturing process. With similar performance and stability, processing of ASD pellets showed the advantages of a superior yield (>98%), ready to use for subsequent processing into multiple unit pellet systems. Therefore, ASD-layered pellets are an attractive alternative in ASD-formulation, especially in early formulation development at limited availability of drug substance.

Solventless amorphization and pelletization using a high shear granulator. Part I; feasibility study using indomethacin

The aim of the current study was to investigate the feasibility of solventless amorphization and pelletization using a high shear granulator, to produce amorphous drug-layered pellets by simply mixing drug crystals and inactive spheres without using solvent and heating. Indomethacin crystals were mixed with microcrystalline cellulose spheres at a weight ratio of 1:10 using the granulator and the resulting particles were then characterized using solid-state and particle analytical techniques as well as pharmaceutically relevant tests. Amorphization of indomethacin crystals progressed with increasing processing time and decreasing jacket temperature. The amorphization rate increased as the spheres became larger and full amorphization was achieved using spheres of 414 and 649 μm in diameter. Indomethacin crystals were pulverized due to mechanical activation by the spheres and the resulting amorphous microparticles were then deposited on the spheres, yielding pellets with an amorphous layer. The pellets exhibited supersaturation characteristics and the dissolution rate was faster than that of quench-cooled indomethacin powder. However, the amorphous drug deposited on the pellets exhibited a lower physical stability than quench-cooled amorphous indomethacin, but recrystallization could be inhibited by co-processing with polyvinylpyrrolidone K-25 stabilizing the amorphous form. The findings suggest the feasibility of the solventless amorphization and pelletization technique.

Solventless amorphization and pelletization using a high shear granulator. Part II; Preparation of co-amorphous mixture-layered pellets using indomethacin and arginine

The aim of this study was to investigate the preparation of co-amorphous mixture-layered pellets using solventless pelletization and amorphization using a high shear granulator (as suggested in the first part of this study) by high shear mixing of drug crystals and a crystalline co-former with inactive spheres. Mixtures of crystalline indomethacin and arginine at various molar ratios were mixed with microcrystalline cellulose spheres at a weight ratio of 1:10 using the granulator and the resulting particles were characterized using solid-state and particle analytical techniques as well as dissolution testing and physical stability. At jacket temperatures of 20 °C or more of the granulator, co-processing of indomethacin and arginine enhanced amorphization of indomethacin and provided a co-amorphous mixture due to homogenous mixing of indomethacin and arginine amorphous phases. The co-amorphous mixture was deposited on the surface of the spheres, yielding co-amorphous mixture-layered pellets. The co-amorphous mixtures at molar ratios of indomethacin to arginine of 2:1 and 1:1, deposited on the pellets, did not recrystallize for at least 4 weeks. The pellets exhibited higher dissolution characteristics as additional hypromellose could prevent precipitation. These findings demonstrate the potential of this technique as a solventless approach to prepare co-amorphous mixture-layered pellets through a one-step process.

Solid dispersion technology as a formulation strategy for the fabrication of modified release dosage forms: A comprehensive review

Solubility limited bioavailability is one of the crucial parameters that affect the formulation development of the new chemical entities. Thus the major constraint in the pharmaceutical product development is the suitable solubility enhancement technique for Active Pharmaceutical Ingredient. Solid dispersion (SD) is an established and preferred method for improving the solubility which ultimately may be helpful to enhance bioavailability. For long period of time Amorphous solid dispersion (ASD) have been preferred for improving solubility, but since last two decades, ASD approach have been combined with different modified release approaches to improvise the stability and site specificity of SD to grasp a hold over the specific advantages associated with such dosage forms. It is an established fact now that the SD technique not only improves solubility limited bioavailability, but it may be combined with other approaches to modify the drug release profile from the formulation as per the requirement based on the apt selection of SD carriers and suitable technology. This review covers the comprehensive overview of all such formulations where SD technology is used to serve dual purpose rather than only the sole purpose of solubility enhancement. The SD approach has been successfully implemented for some of the poorly soluble herbal drugs and still there is a vast scope of advancement in that area. The current review will provide a broad outcome in the area of SD technology for modified release formulations along with the description of current status and future prospective of SD. The SD formed by dispersing drug within the conventional carrier to form ASD increases solubility, dissolution rate and bioavailability; whereas fourth generation hydrophobic carriers provide added advantage of controlled release (CR) or sustained release (SR) profile along with enhanced stability of SD. On the other frontier, pH dependant carriers enable the SD to achieve site specificity or delayed release (DR) profile.

Computational Modeling of Fluidized Beds with a Focus on Pharmaceutical Applications: A Review

The fluidized bed is an essential and standard equipment in the field of process development. It has a wide application in various areas and has been extensively studied. This review paper aims to discuss computational modeling of a fluidized bed with a focus on pharmaceutical applications. Eulerian, Lagrangian, and combined Eulerian-Lagrangian models have been studied for fluid bed applications with the rise of modeling capabilities. Such models assist in optimizing the process parameters and expedite the process development cycle. This paper discusses the background of modeling and then summarizes research papers relevant to pharmaceutical unit operations.

Pharmaceutical amorphous solid dispersion: A review of manufacturing strategies

Amorphous solid dispersions (ASDs) are popular for enhancing the solubility and bioavailability of poorly water-soluble drugs. Various approaches have been employed to produce ASDs and novel techniques are emerging. This review provides an updated overview of manufacturing techniques for preparing ASDs. As physical stability is a critical quality attribute for ASD, the impact of formulation, equipment, and process variables, together with the downstream processing on physical stability of ASDs have been discussed. Selection strategies are proposed to identify suitable manufacturing methods, which may aid in the development of ASDs with satisfactory physical stability.

Preparation and characterization of curcumin solid dispersion using HPMC

Curcumin solid dispersions were prepared using hydroxypropyl methylcellulose (HPMC) to enhance water solubility of curcumin. The particle size of curcumin solid dispersions was in range from 371 to 528 nm and particles were shaped as spherical with wrinkles. The encapsulation efficiency was over 93% for all samples, and water solubility of curcumin was significantly improved to 238 µg/mL when the ratio of curcumin to HPMC was 20:80. The results of X-ray diffraction, differential scanning calorimeter, and Fourier transform infrared spectroscopy showed that crystalline form of curcumin changed to amorphous form. Curcumin solid dispersions showed improved dissolution behavior compared to pure curcumin and the curcumin release kinetic studies were applied to find best-fitting model. This study showed a great potential of solid dispersion using HPMC as curcumin delivery system with improved water solubility and oral absorption. PRACTICAL APPLICATION: Curcumin has limited applications in the food industry because of low water solubility. Dongoh water-soluble curcumin (DW-CURs) were prepared by solid dispersion method with HPMC. Our results indicated that curcumin solid dispersions improved the water solubility of curcumin and showed a sustained release, demonstrating its possibility of body application. Therefore, DW-CURs are a promising formulation for application as a functional ingredient in the food industry.

Manufacturing strategies to develop amorphous solid dispersions: An overview

Since the past several decades, poor water solubility of existing and new drugs in the pipeline have remained a challenging issue for the pharmaceutical industry. Literature describes several approaches to improve the overall solubility, dissolution rate, and bioavailability of drugs with poor water solubility. Moreover, the development of amorphous solid dispersion (SD) using suitable polymers and methods have gained considerable importance in the recent past. In the present review, we attempt to discuss the important and industrially scalable thermal strategies for the development of amorphous SD. These include both solvent (spray drying and fluid bed processing) and fusion (hot melt extrusion and KinetiSol®) based techniques. The current review also provides insights into the thermodynamic properties of drugs, their polymer miscibility and solubility, and their molecular dynamics to develop stable and more efficient amorphous SD.

Development and Evaluation of Poorly Water-Soluble Celecoxib as Solid Dispersions Containing Nonionic Surfactants Using Fluidized-Bed Granulation

The purpose of this study is to develop a solid dispersion system with improved dissolution, absorption, and patient compliance of poorly water-soluble celecoxib (CXB). Instead of sodium lauryl sulfate (SLS), an anionic surfactant used in the marketed product (Celebrex^®), solubilization was performed using non-ionic surfactants with low toxicity. Cremophor RH40 (Cre-RH) was selected as the optimal solubilizer. Granules and tablets containing CXB and Cre-RH were prepared via fluid-bed and tableting processes, respectively. The morphology, crystallinity, flowability, dissolution, and pharmacokinetics for CXB-solid dispersion granules (SDGs) and the hardness and friability for CXB-solid dispersion tablets (SDTs) were evaluated. The solubility of CXB was found to be increased by about 717-fold when using Cre-RH. The dissolution of granules containing Cre-RH was found to be increased greatly compared with CXB API and Celebrex^® (66.9% versus 2.3% and 37.2% at 120 min). The improvement of the dissolution was confirmed to be the same as that of granules in tablets. The CXB formulation resulted in 4.6- and 4.9-fold higher AUC_inf and C_max of CXB compared with those of an oral dose of CXB powder in rats. In short, these data suggest that the solid dispersion based on Cre-RH—a non-toxic solubilizer, non-ionic surfactant— may be an effective formulation for CXB to enhance its oral bioavailability and safety.

In Situ Cocrystallization of Dapsone and Caffeine during Fluidized Bed Granulation Processing

Different pharmaceutical manufacturing processes have been demonstrated to represent feasible platforms for the production of pharmaceutical cocrystals. However, new methods are needed for the manufacture of cocrystals on a large scale. In this work, the suitability of the use of a fluidized bed system for granulation and concomitant cocrystallization was investigated. Dapsone (DAP) and caffeine (CAF) have been shown to form a stable cocrystal by simple solvent evaporation. DAP is the active pharmaceutical ingredient (API) and CAF is the coformer. In the present study, DAP-CAF cocrystals were produced through liquid-assisted milling and the product obtained was used as a cocrystal reference. The granulation of DAP and CAF was carried out using four different experimental conditions. The solid-state properties of the constituents of the granules were characterised by differential scanning calorimetry (DSC) and x-ray powder diffraction (PXRD) analysis while the granule size distribution and morphology were investigated using laser diffraction and scanning electron microscopy (SEM), respectively. DAP-CAF cocrystal granules were successfully produced during fluidized bed granulation. The formation of cocrystals was possible only when the DAP and CAF were dissolved in the liquid phase and sprayed over the fluidized solid particles. Furthermore, the presence of polymers in solution interferes with the cocrystallization, resulting in the amorphization of the DAP and CAF. Cocrystallization via fluidized bed granulation represents a useful tool and a feasible alternative technique for the large scale manufacture of pharmaceutical cocrystals for solid dosage forms.

Preparation of Fine Particles with Improved Solubility Using a Complex Fluidized-Bed Granulator Equipped with a Particle-Sizing Mechanism

A new type of fluidized-bed granulator equipped with a particle-sizing mechanism was used for the preparation of fine particles that improved the solubility of a poorly water-soluble drug substance. Cefteram pivoxyl (CEF) was selected as a model drug substance, and its solution with a hydrophilic polymer, hydroxypropyl cellulose (HPC-L), was sprayed on granulation grade lactose monohydrate (Lac). Three types of treated particles were prepared under different conditions focused on the spraying air pressure and the amount of HPC-L. When the amount of HPC-L was changed, the size of the obtained particles was similar. However, particle size distribution was dependent on the amount of HPC-L. Its distribution became more homogenous with greater amounts of HPC-L, but the particle size distribution obtained by decreasing the spraying air pressure was not acceptable. By processing CEF with HPC-L using a complex fluidized-bed granulator equipped with a particle-sizing mechanism, the dissolution ratio was elevated by approximately 40% compared to that of unprocessed CEF. Moreover, in the dissolution profile of treated CEF, the initial burst was suppressed, and nearly zero order release was observed up to approximately 60% in the dissolution profile. This technique may represent a method with which to design fine particles of approximately 100 µm in size with a narrow distribution, which can improve the solubility of a drug substance with low solubility.

In vitro characterization of a novel polymeric system for preparation of amorphous solid drug dispersions

Preparation of amorphous solid dispersions using polymers is a commonly used formulation strategy for enhancing the solubility of poorly water-soluble drugs. However, often a single polymer may not bring about a significant enhancement in solubility or amorphous stability of a poorly water-soluble drug. This study describes application of a unique and novel binary polymeric blend in preparation of solid dispersions. The objective of this study was to investigate amorphous solid dispersions of glipizide, a BCS class II model drug, in a binary polymeric system of polyvinyl acetate phthalate (PVAP) and hypromellose (hydroxypropyl methylcellulose, HPMC). The solid dispersions were prepared using two different solvent methods: rotary evaporation (rotavap) and fluid bed drug layering on sugar spheres. The performance and physical stability of the dispersions were evaluated with non-sink dissolution testing, powder X-ray diffraction (PXRD), and modulated differential scanning calorimetry (mDSC). PXRD analysis demonstrated an amorphous state for glipizide, and mDSC showed no evidence of phase separation. Non-sink dissolution testing in pH 7.5 phosphate buffer indicated more than twofold increase in apparent solubility of the drug with PVAP-HPMC system. The glipizide solid dispersions demonstrated a high glass transition temperature (Tg) and acceptable chemical and physical stability during the stability period irrespective of the manufacturing process. In conclusion, the polymeric blend of PVAP-HPMC offers a unique formulation approach for developing amorphous solid dispersions with the flexibility towards the use of these polymers in different ratios and combined quantities depending on drug properties.

Strategies to address low drug solubility in discovery and development

Drugs with low water solubility are predisposed to low and variable oral bioavailability and, therefore, to variability in clinical response. Despite significant efforts to "design in" acceptable developability properties (including aqueous solubility) during lead optimization, approximately 40% of currently marketed compounds and most current drug development candidates remain poorly water-soluble. The fact that so many drug candidates of this type are advanced into development and clinical assessment is testament to an increasingly sophisticated understanding of the approaches that can be taken to promote apparent solubility in the gastrointestinal tract and to support drug exposure after oral administration. Here we provide a detailed commentary on the major challenges to the progression of a poorly water-soluble lead or development candidate and review the approaches and strategies that can be taken to facilitate compound progression. In particular, we address the fundamental principles that underpin the use of strategies, including pH adjustment and salt-form selection, polymorphs, cocrystals, cosolvents, surfactants, cyclodextrins, particle size reduction, amorphous solid dispersions, and lipid-based formulations. In each case, the theoretical basis for utility is described along with a detailed review of recent advances in the field. The article provides an integrated and contemporary discussion of current approaches to solubility and dissolution enhancement but has been deliberately structured as a series of stand-alone sections to allow also directed access to a specific technology (e.g., solid dispersions, lipid-based formulations, or salt forms) where required.

Solid dispersion formulations of megestrol acetate with copovidone for enhanced dissolution and oral bioavailability

In order to enhance the dissolution profile and oral bioavailability of megestrol acetate (MA), solid dispersions of MA (MASDs) were formulated with copovidone and crystal sugar as a hydrophilic polymeric carrier and an inert core bead, respectively. Solvent evaporation method and fluidized bed coating technique were employed. MASDs were categorized as crystalline solid dispersion by the characterization of differential scanning calorimetry and X-ray diffraction. The mass-median diameters of MASDs were in a range of 1.4 to 2.6 μm. Based on drug to polymer ratio, MASD (1:1) and (1:2) were considered as optimized formulations, resulting in a smooth-surfaced homogeneously coated layer with enhanced dissolution rate. Dissolution of MASD was gradually increased up to 15 min, after which it reached a plateau. For the initial period, dissolution rates were in the decreasing order of MASD (1:2) ≥ MASD (1:1) > MASD (1:3) > MASD (1:5) > MASD (1:0.5) > MA powder. In the comparative pharmacokinetic study with Megace OS, a reference drug product, MASD (1:1) showed improved bioavailability of over 220% with 2-fold higher C(max) and 30% faster T(max). We conclude that MASD (1:1) is a good candidate for the development of oral solid dosage forms.

Review: physical chemistry of solid dispersions

Objectives

With poorly soluble drug candidates emerging in the drug discovery pipeline, the importance of the solid dispersion formulation approach is increasing. This strategy includes complete removal of drug crystallinity, and molecular dispersion of the poorly soluble compound in a hydrophilic polymeric carrier. The potential of this technique to increase oral absorption and hence bioavailability is enormous. Nevertheless, some issues have to be considered regarding thermodynamic instability, as well in supersaturated solutions that are formed upon dissolution as in the solid state.

Key findings

After a brief discussion on the historical background of solid dispersions and their current role in formulation, an overview will be given on the physical chemistry and stability of glass solutions as they form supersaturated solutions, and during their shelf life.

Conclusions

Thorough understanding of these aspects will elicit conscious evaluation of carrier properties and eventually facilitate rational excipient selection. Thus, full exploitation of the solid dispersion strategy may provide an appropriate answer to drug attrition due to low aqueous solubility in later stages of development.

Preparation, Characterization and Evaluation of Coenzyme Q10 Binary Solid Dispersions for Enhanced Solubility and Dissolution

Phase solubility behavior of coenzyme Q10 (CoQ10) at 25 degrees C in various molar solutions of poloxamer 188 (P188) in water was observed and their binary solid dispersions (BSD) at different weight ratios were prepared by a simple, rapid, cost effective, uncomplicated and potentially scalable low temperature melting method. BSDs were characterized by scanning electron microscopy (SEM) and differential scanning calorimetry (DSC), and evaluated for improved solubility at 25 degrees C and 37 degrees C and in-vitro release of CoQ10 at 37 degrees C in distilled water. Solubility of CoQ10 increased with increasing concentrations of P188 in water. Gibbs free energy (deltaG(o)tr) values were all negative indicating the spontaneous nature of CoQ10 solubilization and decreased with increasing concentration of P188 demonstrating that the reaction conditions became more favorable as the concentration of P188 increased. DSC and SEM analysis indicated that the homogeneity of dispersion was not at the molecular level. However, BSDs exhibited a remarkably improved aqueous solubility and dissolution of CoQ10.

Characterization of Dual Layered Pellets for Sustained Release of Poorly Water-Soluble Drug

The aim of this study was to develop pellet formulations that could be used to improve the dissolution and bioavailability of a poorly water-soluble model drug, cisapride. Six different types of pellets were prepared by coating sugar spheres in a fluidized bed coater. When the sugar spheres were single layered containing cisapride and solubilizer such as polysorbate 80, the resulting pellets provided an instant release of cisapride in the simulated gastric fluid. Dissolution tests carried out in the simulated intestinal fluid showed that there were negligible amounts of cisapride released, regardless of the pellet formulation. To succeed in attaining dissolution and the sustained release of cisapride at a neural pH, the single layered pellets were coated again with a coating suspension containing Eudragit RS 30D and L 30D. Scanning electron microscopy revealed that the dual layered pellets had a crack-free and spherical surface. Interestingly, the dual layered pellets provided the sustained release of cisapride in both the simulated gastric and intestinal fluids. The composition and components of the dual layers were found to be key parameters affecting the pattern of cisapride dissolution. Significant improvement in the bioavailability of cisapride was achieved when the dual layered pellets were administered orally to dogs. Overall, these results suggest that the dual layered pellets have potential as a sustained release dosage form for poorly water-soluble drugs.

Industrially feasible alternative approaches in the manufacture of solid dispersions: a technical report

The purpose of this report was to compile relevant technical information on various alternative strategies that can be used as feasible approaches in the development of solid dispersions. The technologies discussed in the report are spray coating on sugar beads with a fluidized bed coating system, hot melt extrusion, direct capsule filling, electrostatic spinning, surface active carriers, and supercritical fluid technology. The focus is on basic principles, the equipment involved, and the relevant scale-up work. These technologies have been found to eliminate several drawbacks posed by the conventional methods of manufacturing of solid dispersions such as laborious preparation methods, reproducibility, scaling up of manufacturing processes, stability of drug, and vehicle.

A new self-emulsifying formulation of itraconazole with improved dissolution and oral absorption

To enhance the dissolution and oral absorption of poorly water-soluble itraconazole, self-emulsifying drug delivery system (SEDDS) composed of oil, surfactant and cosurfactant for oral administration of itraconazole was formulated, and its physicochemical properties and pharmacokinetic parameters of itraconazole were evaluated. Among the surfactants and oils studied, Transcutol, Pluronic L64 and tocopherol acetate were chosen that showed the maximal solubility to itraconazole. The solubility of itraconazole was further improved by the addition of hydrochloric acid. Droplet size of itraconazole emulsion was kept constant both in simulated gastric fluid without pepsin (pH 1.2) and simulated intestinal fluid (pH 6.8) throughout 120-min incubation period. Itraconazole in the SEDDS rapidly dissolved in every dissolution medium whereas the Sporanox showed different dissolution patterns during the 120-min incubation according to the dissolution media. In fasted and fed normal diet group, AUC(0-->24 h) and the mean maximum plasma level (Cmax) of itraconazole after oral administration of SEDDS in rats were comparable to those of itraconazole after oral dose of Sporanox. However, in fed lipidic diet group, AUC and Cmax after oral administration of SEDDS in rats were 3.7- and 2.8-fold higher, respectively, compared with those of Sporanox. These results demonstrate that the SEDDS of itraconazole composed of Transcutol, Pluronic L64 and tocopherol acetate greatly enhanced the bioavailability of itraconazole after the dose, particularly not influenced by food intake or not. Thus, this system may provide a useful dosage form for oral water-insoluble drug without food effect.

Establishment of new preparation method for solid dispersion formulation of tacrolimus

The aim of this study was to establish a new preparation method for solid dispersion formulation (SDF) of tacrolimus, a poorly water-soluble drug, without dichloromethane, because no use of dichloromethane is recommended by ICH harmonized tripartite guideline. To select the appropriate carrier, three different SDFs with polyethylene glycol 6000 (PEG 6000), polyvinylpyrrolidone (PVP) and hydroxypropylmethylcellulose (HPMC) were prepared by the conventional solvent method, in which tacrolimus and the carrier were completely dissolved in the mixture of dichloromethane and ethanol. Powder X-ray diffraction (XRD) and differential scanning calorimetry (DSC) patterns indicated that tacrolimus exists in an amorphous state in all three SDFs. The supersaturated dissolution profiles of tacrolimus were observed in all SDFs, and the highest level of supersaturation for tacrolimus was obtained and maintained for 24h from SDF with HPMC. On the other hand, the supersaturated level from SDF with PEG 6000 or PVP decreased rapidly. The in vivo oral absorption study in dogs showed that bioavailability of tacrolimus from SDF with HPMC was remarkably improved compared with the crystalline powder. It was clarified that HPMC is the most appropriate carrier for SDF of tacrolimus. Then, SDF of tacrolimus was prepared by the new method, which allows us to make SDF of tacrolimus by swelling HPMC with ethanol, in which tacrolimus was completely dissolved. This new method does not need dichloromethane. The physicochemical properties of SDF with HPMC prepared by the new method were the same as those of SDF prepared by the conventional solvent method. Furthermore, SDF with HPMC prepared by the new method was still stable after stored at 40 degrees C for 3 months. The pharmacokinetic parameters after oral administration in monkeys showed no significant difference (P>0.01) between SDFs with HPMC prepared by the two methods. In conclusion, we have established the new preparation method for SDF of tacrolimus with HPMC and the new method makes it possible to prepare SDF of tacroliumus without dichloromethane.

Preparation and characterization of coenzyme Q10-Eudragit solid dispersion

A solid dispersion of Coenzyme Q10 and Eudragit L 100-55 was prepared using solvent evaporation method. Solid dispersion, physical mixture, and pure compound were then characterized using differential scanning calorimetry and powder x-ray diffraction. Solubility of CoQ10 in different surfactant media was measured, and a suitable dissolution medium was developed to compare the dissolution patterns of the solid dispersion, physical mixture, and the pure compound. Combining labrasol with different surfactants in dissolution media demonstrated an additive effect on CoQ10 solubility. The solubility of CoQ10 in a 4% Labrasol/2% Cremophor EL solution was 562 microg/ml, which was five times higher than the combined solubility in 5% Labrasol (91 microg/ml) and 5% Cremophor EL (7.8 microg/ml). Moderate change in the crystalline pattern of CoQ10 was observed, which was attributed to solvent displacement rather than the degree of crystallinity change. The dissolution test indicated that the in-vitro release of Coenzyme Q10 from its solid dispersion was much faster than its physical mixture, which in turn was faster than the pure drug. The amount of drug released in 12 hours from solid dispersion, physical mixture, and the pure drug was 100, 26.5 and 12.5% respectively. CoQ10 was photostable throughout the dissolution experiments.

Influence of pluronic F-68 on dissolution and bioavailability characteristics of multiple-layer pellets of nifedipine for controlled release delivery

A multiple-layer design of pellets for nifedipine was developed using pluronic F-68 to enhance dissolution rate. The influence of ratios of nifedipine in the inner layer to that in the outer layer, the ratios of pluronic F-68 to nifedipine in the solid dispersion, and the thickness of the control membrane on dissolution characteristics were investigated. With an increasing ratio of pluronic F-68 to nifedipine, the dissolution rate of nifedipine was gradually promoted and the extent of release was enhanced as well. DSC thermograms illustrate the gradual disappearance or broadening of the nifedipine melting peak with the presence of pluronic F-68. The decrease of the nifedipine ratio in the inner layer and the increase of the ratio of pluronic F-68 to nifedipine in the outer layer can enhance the release of nifedipine. With a fixed nifedipine ratio of 1.5 between the inner layer and the outer layer, increasing the ratio of pluronic F-68 to nifedipine in the outer layer significantly increased the initial release rate of nifedipine. By increasing the nifedipine ratio of the inner layer to the outer layer to 1:1, the increase of coating percentage referenced to the total weight decreased the release rate of nifedipine from the inner layer. The pharmacokinetic bioequivalence between the test product (Cardilate, N-6) and Coracten was found with a multiple-dose oral administration of 20 mg in 12 healthy, normal Chinese male volunteers.

Bioavailability of itraconazole in rats and rabbits after administration of tablets containing solid dispersion particles

A tablet dosage form containing solid dispersions of itraconazole (Asd tablets) was prepared by using the spray-drying and wet granulation methods. The dissolution rate of itraconazole from Asd tablets was fast, with more than 90% released within 10 min, compared to less than 20% for a marketed product, Sporanox capsules. The oral absorption of itraconazole from Asd tablets was determined in rats and rabbits and was compared with that for Sporanox capsules. In the rat, there was no difference between the Asd tablets and Sporanox capsules in the mean area under the curve (AUC) (3089.5 +/- 4332.8 ng.hr/ml and 3653.9 +/- 2348.9 ng.hr/ml, respectively) and Cmax (295.0 +/- 344.5 and 390.5 +/- 169.4 ng/ml, respectively). Also, in the rabbit, no difference was found between the two products in the mean AUC (AUMC; 19357.9 +/- 5117.5 ng.hr/ml and 23382.2 +/- 6236.5 ng.hr/ml, respectively) and Cmax (766.4 +/- 276.5 and 1127.5 +/- 577.9 ng/ml, respectively). Despite the rapid in vitro release characteristics of itraconazole from the Asd tablets, the in vivo absorption of itraconazole was comparable to that of Sporanox capsules, with no difference in Tmax in both animal species. Serum levels of the major active metabolite hydroxyitraconazole were also measured. Itraconazole was rapidly converted to hydroxyitraconazole in both rats and rabbits, but there were species-specific differences in their pharmacokinetics. It is concluded that, in addition to drug solubility and dissolution characteristics, other formulation factors such as the physical state of the drug and the granulation process, may also need to be considered in the prediction of the in vivo absorption of itraconazole based on in vitro data.

Enhanced solubility and dissolution rate of itraconazole by a solid dispersion technique

The aim of the present study was to improve the solubility and dissolution rate of a poorly water-soluble drug, itraconazole, by a solid dispersion technique. Solid dispersion particles of itraconazole were prepared with various pH-independent and -dependent hydrophilic polymers and were characterized by differential scanning calorimetry, powder X-ray diffraction and scanning electron microscopy. Of the polymers tested, pH-dependent hydrophilic polymers, AEA and Eudragit E 100, resulted in highest increases in drug solubility (range, 141.4-146.9-fold increases). The shape of the solid dispersion particles was spherical, with their internal diameter ranging from 1-10 microm. The dissolution rate of itraconazole from the tablets prepared by spray drying (SD-T) was fast, with > 90% released within 5 min.SD-T prepared with AEA or Eudragit E 100 at a 1:1 drug hydrophilic polymer ratio (w/w) showed approximately 70-fold increases in the dissolution rate over a marketed product.

Solid dispersion of poorly water-soluble drugs: early promises, subsequent problems, and recent breakthroughs

Although there was a great interest in solid dispersion systems during the past four decades to increase dissolution rate and bioavailability of poorly water-soluble drugs, their commercial use has been very limited, primarily because of manufacturing difficulties and stability problems. Solid dispersions of drugs were generally produced by melt or solvent evaporation methods. The materials, which were usually semisolid and waxy in nature, were hardened by cooling to very low temperatures. They were then pulverized, sieved, mixed with relatively large amounts of excipients, and encapsulated into hard gelatin capsules or compressed into tablets. These operations were difficult to scale up for the manufacture of dosage forms. The situation has, however, been changing in recent years because of the availability of surface-active and self-emulsifying carriers and the development of technologies to encapsulate solid dispersions directly into hard gelatin capsules as melts. Solid plugs are formed inside the capsules when the melts are cooled to room temperature. Because of surface activity of carriers used, complete dissolution of drug from such solid dispersions can be obtained without the need for pulverization, sieving, mixing with excipients, etc. Equipment is available for large-scale manufacturing of such capsules. Some practical limitations of dosage form development might be the inadequate solubility of drugs in carriers and the instability of drugs and carriers at elevated temperatures necessary to manufacture capsules.