Understanding the Roles of Excipients in Moisture Management in Solid Dosage Forms

Excipients are ubiquitous in pharmaceutical products, and often, they can also play a critical role in maintaining product quality. For a product containing a moisture-sensitive drug, moisture can be deleterious to the product stability during storage. Therefore, using excipients that interact with moisture in situ can potentially alleviate product stability issues. In this study, the interactive behavior of starch with moisture was augmented by coprocessing maize starch with sodium chloride (NaCl) or magnesium nitrate hexahydrate [Mg(NO3)2·6H2O] at different concentrations (5 and 10%, w/w). The effect of the formulation on drug stability was assessed through the degradation of acetylsalicylic acid, which was used as the model drug. The results showed that coprocessing of the starch with either NaCl or Mg(NO3)2·6H2O impacted the number of water molecule binding sites on the starch and how the sorbed moisture was distributed. The coprocessed excipients also resulted in lower drug degradation and lesser changes in tablet tensile strength during post-compaction storage. However, corresponding tablet formulations containing physical mixtures of starch and salts did not yield promising outcomes. This study demonstrated the advantageous concomitant use of common excipients by coprocessing to synergistically mitigate the adverse effects of moisture and promote product stability when formulating a moisture-sensitive drug. In addition, the findings could help to improve the understanding of moisture-excipient interactions and allow for the judicious choice of excipients when designing formulations containing moisture-sensitive drugs.

A new chromanone acid derivative from the nut oil resin of Calophyllum inophyllum

One novel chromanone acid derivative, namely inocalophylline C (1), together with one known compound calophyllolide (2), were isolated from the methanolic extract of nut oil resin of Calophyllum inophyllum L., a medicinal plant widely distributed in Vietnam. The isolated compound structures were elucidated by spectroscopic methods and the absolute configuration of 1 was established by the single-crystal X-ray crystallography as ethyl (R) 3-((2 R,3R,6R)-4-hydroxy-2,3-dimethyl-6-((R)-5-methyl-2-(prop-1-en-2-yl)hex-4-en-1-yl)-6-(3-methylbut-2-en-1-yl)-5,7-dioxo-3,5,6,7-tetrahydro-2H-chromen-8-yl)-3-phenylpropanoate.

Microparticle formulations alter the toxicity of fenofibrate to the zebrafish Danio rerio embryo

A wide variety of active pharmaceutical ingredients are released into the environment and pose a threat to aquatic organisms. Drug products using micro- and nanoparticle technology can lower these emissions into the environment by their increased bioavailability to the human patients. However, due to this enhanced efficacy, micro- and nanoscale drug delivery systems can potentially display an even higher toxicity, and thus also pose a risk to non-target organisms. Fenofibrate is a lipid-regulating agent and exhibits species-related hazards in fish. The ecotoxic effects of a fenofibrate formulation embedded into a hydroxypropyl methylcellulose microparticle matrix, as well as those of the excipients used in the formulation process, were evaluated. To compare the effects of fenofibrate without a formulation, fenofibrate was dispersed in diluted ISO water alone or dissolved in the solvent DMF and then added to diluted ISO water. The effects of these various treatments were assessed using the fish embryo toxicity test, acridine orange staining and gene expression analysis assessed by quantitative RT polymerase chain reaction. Exposure concentrations were assessed by chemical analysis. The effect threshold concentrations of fenofibrate microparticle precipitates were higher compared to the formulation. Fenofibrate dispersed in 20%-ISO-water displayed the lowest toxicity. For the fenofibrate formulation as well as for fenofibrate added as a DMF solution, greater ecotoxic effects were observed in the zebrafish embryos. The chemical analysis of the solutions revealed that more fenofibrate was present in the samples with the fenofibrate formulation as well as fenofibrate added as a DMF solution compared to fenofibrate dispersed in diluted ISO water. This could explain the higher ecotoxicity. The toxic effects on the zebrafish embryo thus suggested that the formulation as well as the solvent increased the bioavailability of fenofibrate.

Effect of Roughness on the Dispersion of Dry Powders for Inhalation: a Dynamic Visualization Perspective

Dry powder inhalers have attracted more interest over the years in every aspect related to them. Interestingly, when focusing on the effects of particle morphology of the active or carrier (excipient), it is generally regarded particle size and shape to influence drug availability of aerosolized particles. However, to date, few studies have examined the effect of texture, i.e., roughness, on this relationship. The main objective of the present work is to gain a closer understanding of the influence of carrier morphology on the aerosolization performance of dry powder inhaler formulations. Image analysis and microscopy were used to visualize the aerosolization process. It is considered that the scale of morphological features on the surface of the carrier particles is responsible for the dispersion of the powder formulation, separation of the drug/carrier, and entrainment from a dry powder inhaler. Thus, for this study, the carrier particles of different surface roughness were mixed with micronized salbutamol sulphate. Aerosolization in vitro testing was used to evaluate the performance. The results indicate a connection between the qualitative surface roughness of coarse carriers and aerosolization performance during powder dispersibility. This investigation demonstrated that indeed, powder dispersion, a dynamic process, is influenced by the scale of the carrier morphology.

Ex-vivo permeation study of chlorin e6-polyvinylpyrrolidone complexes through the chick chorioallantoic membrane model

OBJECTIVE

To investigate the influence of the hydrophilic polymer, polyvinylpyrrolidone (PVP) on the ex-vivo permeability of the poorly water-soluble photosensitizer, chlorin e6 (Ce6) using the chick chorioallantoic membrane (CAM) model.

METHODS

The CAM was removed from the fertilized chicken egg at embryo age of 15 days. The permeation profiles of Ce6 and PVP complexes (Ce6-PVP) at 1:0, 1:1, 1:10, 1:50 and 1:100 w/w in different pH conditions were first studied using the CAM model with Franz diffusion cell over 8 h. The solution viscosity of the formulations and apparent solubility of Ce6 were also investigated.

KEY FINDINGS

The permeability of Ce6 was found to be directly proportional to the amount of PVP used and the apparent solubility of Ce6. Permeability was only marginally affected by the solution viscosity of the formulations. The permeability of Ce6 was lowered in the acidic pH. Ce6-PVP at 1:100 w/w gave the highest percentage release of Ce6 across the CAM, with 23% at pH 3 and 55% at pH 7.4, after 8 h, respectively.

CONCLUSIONS

The present work suggests that PVP had served as penetration enhancer for the poorly water-soluble Ce6 and the CAM can serve as a useful biological membrane model for preclinical permeability study of biological and pharmaceutical substances. The Ce6-PVP formulation at 1:100 w/w can be applied for the further clinical investigation.

The chick chorioallantoic membrane imaging method as a platform to evaluate vasoactivity and assess irritancy of compounds

OBJECTIVE

To determine if the chick chorioallantoic membrane (CAM) is a potential alternative that is capable of screening test substances for vasoactivity in terms of vessel diameter changes. The CAM was also evaluated as a tool for irritancy screening.

METHODS

Visual assessment of the CAM for irritancy after the application of the test substance or solvent to its surface was made. An imaging based-in-vivo CAM model was developed by imaging CAM blood vessels in a pre-defined area using a semi-automatic image processing and analysis technique to measure blood vessel diameters. Solvents and drugs such as 70% v/v ethanol, normal saline, 5% w/v glucose monohydrate, glycerin, glucagon, N-methylpyrrolidone, nicotine, glyceryl trinitrate, glucagon, propranolol and caffeine were tested on the CAM.

KEY FINDINGS

Propranolol, nicotine and glycerin were irritants on CAM. Changes in the diameters of fine blood vessels were accurately measured by high resolution image analysis. Vasoconstriction was seen with 70% v/v ethanol while vasodilation was displayed with glucagon and caffeine. The results reflected expected trends with evidence of feedback mechanisms ensuring homeostasis.

CONCLUSION

The CAM model can be applied to assess pharmaceutical and cosmetic formulations in early development work to gain useful insights to potential irritancy and biological effects of components and formulations.

Evaluation of the physicochemical properties and compaction behavior of melt granules produced in microwave-induced and conventional melt granulation in a single pot high shear processor

Recently, microwave-induced melt granulation was shown to be a promising alternative to conventional melt granulation with improved process monitoring capabilities. This study aimed to compare the physicochemical and compaction properties of granules produced from microwave-induced and conventional melt granulation. Powder admixtures comprising equivalent proportions by weight of lactose 200 M and anhydrous dicalcium phosphate were granulated with polyethylene glycol 3350 under the influence of microwave-induced and conventional heating in a 10-L single pot high shear processor. The properties of the granules and compacts produced from the two processes were compared. Relative to conventional melt granulation, the rates at which the irradiated powders heated up in microwave-induced melt granulation were lower. Agglomerate growth proceeded at a slower rate, and this necessitated longer massing durations for growth induction. These factors prompted greater evaporative moisture losses from the melt granules. Additionally, nonuniform heating of the powders under the influence of microwaves led to increased inter-batch variations in the binder contents of resultant melt granules and a reliance of content homogeneity on massing duration. Agglomerate growth proceeded more rapidly under the influence of conventional heating due to the enhanced heating capabilities of the powders. Melt granules produced using the conventional method possessed higher moisture contents and improved content homogeneity. The compaction behavior of melt granules were affected by their mean sizes, porosities, flow properties, binder, and moisture contents. The last two factors were responsible for the disparities in compaction behavior of melt granules produced from microwave-induced and conventional melt granulation.

Insights into the functionality of pelletization aid in pelletization by extrusion-spheronization

This study investigated the particle sizes of pelletization aids from the different wet processing steps of extrusion-spheronization, and their influence on rheological and pellet properties. Three commercial microcrystalline cellulose (MCC) grades, three commercial cross-linked polyvinyl pyrrolidone (X-PVP) grades and two agglomerated X-PVP grades (prepared using roller compaction from two commercial fine particle size X-PVP grades) were used as pelletization aid. The pelletization aids were analyzed for their dry state particle size, individual particle size (sonicated powder dispersion in water) and in-process particle sizes (dispersions of processed materials from the different processing steps). No remarkable particle size changes were observed with the commercial X-PVP grades under the different conditions. The two fine X-PVP grades, but not the coarse grade, produced good quality pellets. MCC and agglomerated X-PVP grades exhibited spectacularly lower individual and in-process particle sizes, and produced good quality pellets although some of them had dry state particle sizes comparable to that of the commercial coarse X-PVP grade. In-process particle sizes of pelletization aids correlated strongly with the rheological and pellet properties of the pelletization aid:lactose (1:3) binary mixtures. These results demonstrated that small in-process particle size of pelletization aid is a critical requirement for successful pelletization by extrusion-spheronization.

Formulation, biological and pharmacokinetic studies of sucrose ester-stabilized nanosuspensions of oleanolic Acid

PURPOSE

The aim of this study was to develop sucrose ester (SE)-stabilized oleanolic acid (OA) nanosuspensions (NS) for enhanced delivery.

METHODS

SEOA NS were prepared via O/W emulsion and organic solvent evaporation methods. The particles' size and polydispersity index were measured by nanosizer. Their percent encapsulation efficiency, saturation solubility and in vitro dissolution rate were obtained via HPLC. The in vitro bioefficacy was analyzed by MTT measurements in A549 human non-small-cell lung cancer cell line. The cellular uptake of OA and in vivo pharmacokinetics profile were determined using LC-ESI-MS/MS.

RESULTS

Spherical SEOA NS particles (~100 nm in diameter) were produced and found to be physicochemically stable over a month at 4°C. In particular, SEOA 4121 NS (SEL: SEP at 4:1 w/w; SE: OA at 2:1 w/w) produced the greatest increase in saturation solubility (1.89 mg/mL vs. 3.43 μg/mL), dissolution rate, cytotoxicity and bioavailability. Preliminary studies indicated that cellular uptake of SEOA NS by A549 cells was temperature-, concentration- and time-dependent.

CONCLUSION

Preparing OA as SE-stabilized NS particles provides a novel method to enhance saturation solubility, in vitro dissolution rate, bioefficacy and in vivo bioavailability of free OA and/or other potentially useful hydrophobic drugs.

Chick chorioallantoic membrane as an in situ biological membrane for pharmaceutical formulation development: a review

The use of animals in research has always been a debatable issue. Over the past few decades, efforts have been made to reduce, replace, and refine experiments for ethical use of experimental animals. The use of chick chorioallantoic membrane (CAM) was one of the proposed alternatives to the Draize rabbit ocular irritation test with several advantages including simplicity, rapidity, sensitivity, ease of performance, and cost-effectiveness. The recent use of CAM in the development of pharmaceuticals and testing models to mimic human tissue, including drug transport across CAM, will be discussed in this review.

In-vivo optical detection of cancer using chlorin e6--polyvinylpyrrolidone induced fluorescence imaging and spectroscopy

Background

Photosensitizer based fluorescence imaging and spectroscopy is fast becoming a promising approach for cancer detection. The purpose of this study was to examine the use of the photosensitizer chlorin e6 (Ce6) formulated in polyvinylpyrrolidone (PVP) as a potential exogenous fluorophore for fluorescence imaging and spectroscopic detection of human cancer tissue xenografted in preclinical models as well as in a patient.

Methods

Fluorescence imaging was performed on MGH human bladder tumor xenografted on both the chick chorioallantoic membrane (CAM) and the murine model using a fluorescence endoscopy imaging system. In addition, fiber optic based fluorescence spectroscopy was performed on tumors and various normal organs in the same mice to validate the macroscopic images. In one patient, fluorescence imaging was performed on angiosarcoma lesions and normal skin in conjunction with fluorescence spectroscopy to validate Ce6-PVP induced fluorescence visual assessment of the lesions.

Results

Margins of tumor xenografts in the CAM model were clearly outlined under fluorescence imaging. Ce6-PVP-induced fluorescence imaging yielded a specificity of 83% on the CAM model. In mice, fluorescence intensity of Ce6-PVP was higher in bladder tumor compared to adjacent muscle and normal bladder. Clinical results confirmed that fluorescence imaging clearly captured the fluorescence of Ce6-PVP in angiosarcoma lesions and good correlation was found between fluorescence imaging and spectral measurement in the patient.

Conclusion

Combination of Ce6-PVP induced fluorescence imaging and spectroscopy could allow for optical detection and discrimination between cancer and the surrounding normal tissues. Ce6-PVP seems to be a promising fluorophore for fluorescence diagnosis of cancer.

Antimicrobial and antioxidant activities of Cortex Magnoliae Officinalis and some other medicinal plants commonly used in South-East Asia

Background

Eight medicinal plants were tested for their antimicrobial and antioxidant activities. Different extraction methods were also tested for their effects on the bioactivities of the medicinal plants.

Methods

Eight plants, namely Herba Polygonis Hydropiperis (Laliaocao), Folium Murraya Koenigii (Jialiye), Rhizoma Arachis Hypogea (Huashenggen), Herba Houttuyniae (Yuxingcao), Epipremnum pinnatum (Pashulong), Rhizoma Typhonium Flagelliforme (Laoshuyu), Cortex Magnoliae Officinalis (Houpo) and Rhizoma Imperatae (Baimaogen) were investigated for their potential antimicrobial and antioxidant properties.

Results

Extracts of Cortex Magnoliae Officinalis had the strongest activities against M. Smegmatis, C. albicans, B. subtilis and S. aureus. Boiled extracts of Cortex Magnoliae Officinalis, Folium Murraya Koenigii, Herba Polygonis Hydropiperis and Herba Houttuyniae demonstrated greater antioxidant activities than other tested medicinal plants.

Conclusion

Among the eight tested medicinal plants, Cortex Magnoliae Officinalis showed the highest antimicrobial and antioxidant activities. Different methods of extraction yield different spectra of bioactivities.

A study on microwave-induced melt granulation in a single pot high shear processor

Microwave-induced high shear melt granulation was compared with conventional melt granulation performed in the same processor. Admixtures of lactose 200M and anhydrous dicalcium phosphate were granulated with polyethylene glycol 3350. Different heating mechanisms in the two processes necessitated the use of different parameters for process monitoring and control. Mixer power consumption was suitable for monitoring agglomerate growth under microwave-induced heating. Product temperature was a better indicator of agglomeration propensity in conventional melt granulation. These were attributed to the disparities in heat acquisition rates and heating uniformities of the powders as well as variation in baseline mixer power consumption between the two processes.

New Indices to Characterize Powder Flow Based on Their Avalanching Behavior

Use of powder avalanches in the study of flow properties of pharmaceutical excipients has yet to be popularized even though it is rather simple to use and yields comparatively reliable results. Commonly employed flow assessment methods include compressibility studies and shear cell and repose angle measurements. Though widely accepted, these methods are not without limitations and inadequacies. More often than not, experimental and environmental conditions lead to a considerable amount of variability in the results obtained. The primary objective of this current work is to propose two new indices, avalanche flow index (AFI) and cohesive interaction index (CoI) based on the avalanche flow behaviors of powders. Not only were these two indices able to describe the ease of powder flow but they also provided a simpler means of quantifying the extent of cohesive interactions within the powder mass without elaborate mathematical functions.

Effect of oil loading on microspheres produced by spray drying

Oil-loaded microspheres were produced by spray drying emulsions consisting of fish oil and modified starch suspensions with different oil loadings. The emulsion stability was assessed by oil droplet size analysis. Microspheres were characterized in terms of size, morphology, yield and microencapsulation efficiency. It was found that an increase in oil loading resulted in emulsions containing larger oil droplets. This corresponded with larger mean microsphere diameters and rounder microspheres. However, high oil loadings produced lower yields and affected microencapsulation efficiencies.

Investigation of the release of aspirin from spray-congealed micro-pellets

The release behaviour of aspirin from spray-congealed hydrogenated soybean oil micro-pellets of different sizes was studied. The purpose of this study was to investigate the effect of particle size of micro-pellets on the drug release profile and mechanism. Micro-pellets produced were sieved into several fractions and their drug content and dissolution profiles in two media were determined. The dissolution mechanism was studied by fitting the data to release kinetic models. Micro-pellets with high encapsulation efficiency were successfully produced. The micro-pellets were able to sustain the release of aspirin in pH 1.2 and pH 6.8 dissolution media. As particle size of micro-pellets increased, the drug release rate decreased. The drug release mechanism was affected by the size of micro-pellets. Micro-pellets in the range of 90-250 microm tended to follow the first order or Higuchi model. However, micro-pellets in the range of 250-355 microm were found to follow zero-order release model. This result showed that drug release could be modified by controlling the size of micro-pellets and that controlled release of drug might be achieved by using larger size micro-pellets.

Importance of small pores in microcrystalline cellulose for controlling water distribution during extrusion-spheronization

The purpose of this research was to investigate the effects of particle size on the wet massing behavior of microcrystalline cellulose (MCC). In this study, a series of six fractionated MCC grades were customized and specially classified to yield different particle size varieties of the standard grade, Comprecel M101. All seven MCC grades were extensively characterized for the physical properties and wet massing behavior using mixer torque rheometry. Effects of MCC physical properties on the maximum torque (Torque(max)) were determined using partial least squares (PLS) analysis. Most physical properties varied systematically with particle size and morphological changes. Marked differences were observed in the small pore volumes (V (highP)) and BET surface areas of the MCC grades. Variables that exerted dominant influences on Torque(max) were identified. In particular, the significance of V (highP) in governing wet mass consistency was established. The role of V (highP) has not been reported in any study because this small but significant variation is likely to be obliterated or compensated by variation in other physical properties from MCC grades from different suppliers. The findings demonstrated the role of small pores in governing the wet mass consistency of MCC and provide a better understanding of MCC's superior performance as a spheronization aid by the ability to fulfill the function as a molecular sponge to facilitate pellet formation during wet granulation processes.

Impact of cross-linker on alginate matrix integrity and drug release

Sodium alginate, a biopolymer, was employed in the formulation of matrix tablets. They cracked or laminated at acidic pH, compromising their dissolution performance. Improved mechanical strength and reduced barrier permeability of calcium alginate gel provided the rationale for cross-linking the alginate matrix to sustain drug release. Studies had suggested that the incorporation of soluble calcium salts in alginate matrix tablets could sustain drug release at near-neutral pH due to in situ cross-linking. However, results from the present study showed otherwise when gastrointestinal pH conditions were simulated. Significant reduction in drug release rate was only observed when an external calcium source was utilized at low concentration. High calcium ion concentrations caused matrix disintegration. In contrast, matrices pre-coated by calcium alginate could sustain drug release at pH 1.2 followed by pH 6.8 for over 12h. The presence of cross-linked barrier impeded matrix lamination and preserved matrix structure, contributing to at least three-fold reduction in drug release at pH 1.2. Zero order release as well as delayed burst release could be achieved by employing appropriate grade of alginate and cross-linking conditions.

Process analytical technology: application to particle sizing in spray drying

The purpose of this research was to explore the possibility of employing PAT for particle sizing during spray drying with the use of an in-line and at-line laser diffraction system. Microspheres were made using maltodextrin and modified starch as wall material and size results obtained using PAT compared with those determined with off-line laser diffraction and light microscopy. Median particle size results were highest for in-line laser diffraction, followed by at-line and off-line laser diffraction and finally light microscopy. This was due to the presence of agglomerates which were measured as discrete microspheres in the in-line set-up. At-line and off-line laser diffraction gave results more closely correlated with individual microsphere sizes due to agglomerate breakdown during the measurement process. Light microscopy allowed direct observation of the particle morphology, however, its use for particle sizing was tedious and sample size was much smaller compared to laser diffraction. Although PAT was found to be an efficient and convenient tool, careful data interpretation was needed taking into account the cohesiveness of the material measured. The at-line set-up appeared to be more suitable in this particular application.

Chlorin e6 - polyvinylpyrrolidone mediated photosensitization is effective against human non-small cell lung carcinoma compared to small cell lung carcinoma xenografts

Background

Photodynamic therapy (PDT) is an effective local cancer treatment that involves light activation of a photosensitizer, resulting in oxygen-dependent, free radical-mediated cell death. Little is known about the comparative efficacy of PDT in treating non-small cell lung carcinoma (NSCLC) and small cell lung carcinoma (SCLC), despite ongoing clinical trials treating lung cancers. The present study evaluated the potential use of chlorin e6 – polyvinylpyrrolidone (Ce6-PVP) as a multimodality photosensitizer for fluorescence detection and photodynamic therapy (PDT) on NSCLC and SCLC xenografts.

Results

Human NSCLC (NCI-H460) and SCLC (NCI-H526) tumor cell lines were used to establish tumor xenografts in the chick chorioallantoic membrane (CAM) model as well as in the Balb/c nude mice. In the CAM model, Ce6-PVP was applied topically (1.0 mg/kg) and fluorescence intensity was charted at various time points. Tumor-bearing mice were given intravenous administration of Ce6-PVP (2.0 mg/kg) and laser irradiation at 665 nm (fluence of 150 J/cm² and fluence rate of 125 mW/cm²). Tumor response was evaluated at 48 h post PDT. Studies of temporal fluorescence pharmacokinetics in CAM tumor xenografts showed that Ce6-PVP has a selective localization and a good accuracy in demarcating NSCLC compared to SCLC from normal surrounding CAM after 3 h post drug administration. Irradiation at 3 h drug-light interval showed greater tumor necrosis against human NSCLC xenografts in nude mice. SCLC xenografts were observed to express resistance to photosensitization with Ce6-PVP.

Conclusion

The formulation of Ce6-PVP is distinctly advantageous as a diagnostic and therapeutic agent for fluorescence diagnosis and PDT of NSCLC.

Formulation of Hydrophilic Non-Aqueous Gel: Drug Stability in Different Solvents and Rheological Behavior of Gel Matrices

PURPOSE

This study was aimed at formulating a hydrophilic non-aqueous gel for topical delivery of the model moisture-sensitive drug, minocycline hydrochloride (MH).

METHODS

Stability study of MH dissolved in water and various hydrophilic non-aqueous solvents was performed over a period of four months in order to select a suitable non-aqueous solvent for MH gel. To improve MH stability, the effect of different cation additives on MH stability in the selected solvent was investigated. Non-aqueous gel matrices were prepared from three different types of hydrophilic polymers in glycerin-propylene glycol mixture with Mg(2+) cation additive. Oscillatory shear rheometry was performed on the gel matrices using a cone-and-plate rheometer.

RESULTS

MH stability was affected by the type of solvent employed and the duration of storage. Different cation additives affected the extent of MH stabilization through MH-cation complex formation. Rheological properties of the non-aqueous gel matrices were significantly affected by the type and concentration of polymer, and the vehicle ratios in the formulations.

CONCLUSIONS

MH stabilization could be achieved using the selected glycerin-propylene glycol mixture containing MgCl(2). Gel matrix formulated using this solvent system and 3%w/w N-vinylacetamide/sodium acrylate copolymer had demonstrated the most favorable rheological properties as a gel for topical application.

A novel fiber-optic photometer for in situ stability assessment of concentrated oil-in-water emulsions

The purpose of this research was to evaluate a novel fiber-optic photometer for its ability to monitor physical instabilities occurring in concentrated emulsions during storage. For this, the fiber-optic photometer was used to measure transmission of oil-in-water emulsions stabilized with hypromellose (HPMC) as a function of oil volume fraction and droplet size distribution (DSD). To detect physical instabilities like creaming and coalescence, the transmissivity of the samples was studied at 2 different height levels over a certain period of time. The corresponding droplet size distributions were determined by laser diffraction with PIDS. Transmissivity was found to depend on the number of dispersed droplets and thus is sensitive to both the variation of phase volume fraction as well as the emulsions droplet size distribution. At constant DSD, light transmission decreased linearly with increasing oil content within a large interval of phase volume fractions from 0.01 to 0.3. At constant phase volume fraction, an increase in droplet size increased light transmission. Investigation of creaming on emulsions with different droplet size distributions showed changes in the initial delay times and creaming velocities. In contrast to creaming phenomenon coalescence can be identified by height independent changes of the transmissivity. In conclusion, transmissivity of oil-in-water emulsions observed by the novel fiber-optic photometer is sensitive to phase volume fraction, droplet size distribution, and thus can be used as a tool for stability studies on concentrated emulsions.

Study of coat quality of tablets coated by an on-line Supercell coater

The aim of this study was to investigate the nature of Supercell coating, an on-line tablet coater that employed a unique pattern of airflow. Tablets coated at different spray rates (4, 6, 8, 10, and 12 mL/min) were analyzed to investigate the influence of different wetting conditions on the quality of coats formed. Scanning electron micrographs showed that tablet coats formed at a spray rate of 4 mL/min consisted of spray-dried droplets that did not coalesce. At a spray rate of 6 mL/min, surface roughness was found to be lower than at the other spray rates, and the coat appeared smoothest, whereby droplets seemed fused together. At higher spray rates, the droplets appeared as branching arms and scale-like structures. This was attributed to the spread of spray droplets by the processing air and mass transfer of wet coating materials between tablets. Further tests showed that coats formed at higher spray rates had higher drug yield, drug uniformity, color uniformity, and density. However, the variability in coat thickness was increased due to the mass transfer of coats and dissolution of tablet core surfaces by the coating material. Since coats of different characteristics can be formed in Supercell coating, the choice of wetting conditions would depend on the type of coat required and the coating materials used.

Elucidation of spheroid formation with and without the extrusion step

Spheroid formation mechanisms were investigated using extrusion-spheronization (ES) and rotary processing (RP). Using ES (cross-hatch), ES (teardrop), and RP (teardrop), spheroids with similar mass median diameter (MMD) and span were produced using equivalent formulation and spheronization conditions. During spheronization, the teardrop-studded rotating frictional surface, with increased peripheral tip speed and duration, produced spheroids of equivalent MMD and span to those produced by the cross-hatch rotating frictional plate surface. The roundness of these spheroids was also similar. RP required less water to produce spheroids of MMD similar to that of spheroids produced by ES. However, these RP spheroids were less spherical. Image analysis of 625 spheroids per batch indicated that the size distribution of RP spheroids had significantly greater SD, positive skewness, and kurtosis. Morphological examination of time-sampled spheroids produced by ES indicated that spheroid formation occurred predominantly by attrition and layering, while RP spheroids were formed by nucleation, agglomeration, layering, and coalescence. RP produced spheroids with higher crushing strength than that of ES-produced spheroids. The amount of moisture lost during spheronization for spheroids produced by ES had minimal influence on their eventual size. Differences in process and formulation parameters, in addition to size distribution and observed morphological changes, enabled a greater understanding of spheroid formation and methods to optimize spheroid production.

Influence of particle wall adhesion on particle electrification in mixers

In this work, particle electrification in the Turbula and horizontally oscillating mixers were investigated for adipic acid, microcrystalline cellulose (MCC), and glycine particles. MCC and glycine particles acquired positive electrostatic charges, while adipic acid particles attained negative charges in both mixers. Adipic acid (of sieved size larger than 500 microm), MCC, and glycine particles were monotonically charged to saturated values, and had negligible wall adhesion. On the contrary, the adipic acid particles, both unsieved and sieved but of smaller sieved size fraction, exhibited very different charging kinetics in the horizontally oscillating mixer. These adipic acid particles firstly acquired charges up to a maximum value, and then the charges slowly reduced to a lower saturated value with increasing mixing time. Furthermore, these particles were found to adhere to the inner wall of the mixer, and the adhesion increased with mixing time. Surface specific charge densities for adipic acid particles were estimated based on particle size distribution, and were found to increase with particle mean diameters under the conditions investigated. The results obtained from the current work suggested that electrostatic force enhanced particle-wall adhesion, and the adhered particles can have a significant impact on particle electrification.

Use of swirling airflow to enhance coating performance of bottom spray fluid bed coaters

As there is strong interest in coating increasingly smaller particles or pellets for use in compacted dosage forms, there is a need for better small particle coating systems. This study explored the use of swirling airflow to enhance the performance of the bottom spray coating system. Firstly, pellet coating in the non-swirling airflow of conventional Wurster coating was compared with that of swirling airflow in precision coating under standardized conditions. Secondly, precision coating was studied in greater details at different airflow rates (60-100m(3)/h) and partition gaps (6-22mm). Precision coating was found to have higher Reynolds numbers (Re) than Wurster coating, indicating higher turbulence. It produced coated pellets of better properties than Wurster coating, having less agglomeration and gross surface defects, more uniform coats, increased flow and tapped density, and slower drug release. Higher surface roughness did not affect the yield. In precision coating, increasing airflow rates decreased the degree of agglomeration but had minimal effect on pellet quality attributes (colour intensity, colour uniformity and surface roughness) and yields. Increasing partition gaps increased the degree of agglomeration proportionally, but this effect was small. However, greater changes in yield, surface roughness, colour intensity and colour uniformity were detected. This study showed that precision coating, while having a higher drying ability, was able to maintain the same yield and produce coated pellets with superior quality compared to Wurster coating. In precision coating, airflow rate had greater influence on the drying of pellets while partition gap had greater influence on pellet quality attributes.

Feasibility of eliminating premixing for the production of pellets in a rotary processor

This current study aims to explore the feasibility of eliminating the premixing step for making pellets in a rotary processor. Microcrystalline cellulose (MCC) and lactose were used as starting materials. They could be loaded into the rotary processor separately using three different loading configurations (Methods I, II, and III) or as MCC:lactose blend, which was prepared in the separate mixer prior to loading (Method IV). Physical properties of the pellets prepared in Methods I-III were evaluated and compared against those prepared using a premixed blend (Method IV). The effects of loading configuration on pellet quality can be assessed by comparing the pellets prepared in Methods I, II, and III. Physical characterization of pellets included mean size, size distribution, oversized fraction, and shape. No significant difference in pellet properties could be attributed to the effect of premixing. Pellet properties were not significantly affected by the different loading configurations either. This study demonstrated that homogeneous powder blends are not required for the production of pellets in rotary processing. The tumbling action of the powders at the start of rotary processing is sufficient to ensure adequate powder mixing. However, it may be judicious to cofeed the different powders to achieve some preliminary mixing during loading under extreme processing conditions.

Torque rheological parameters to predict pellet quality in extrusion-spheronization

This study explored the feasibility of predicting the quality of microcrystalline cellulose (MCC) pellets prepared by extrusion-spheronization using torque rheological characterization. Rheological properties of eleven MCC grades as well as their binary mixtures with lactose (3:7) at various water contents were determined using a mixer torque rheometer (MTR). Derived torque parameters were: maximum torque and cumulative energy of mixing (CEM). CEM values of MCC powders (CEM((MCC))) could be attributed to their physical properties such as crystallinity, V(low P) and V(total) (volumes of mercury intruded in their pores at low pressure and the total intrusion volume), bulk and tapped densities. For both MCC powders and their binary mixtures, strong correlation was observed between their torque parameters and the properties of their pellets formed with 30 and 35% (w/w) water. Since this relationship was valid over a broad water content range, rheological assessment for pre-formulation purposes need not be performed at optimized water contents. These results demonstrated the usefulness of torque rheometry as an effective means of comparing and evaluating MCC grades especially when substitution of equivalent grades is encountered. In so doing, the tedious and expensive pre-production (pre-formulation and optimization) work can be considerably reduced.

Characterization of microemulsion structures in the pseudoternary phase diagram of isopropyl palmitate/water/Brij 97:1-butanol

This research was aimed to characterize microemulsion systems of isopropyl palmitate (IPP), water, and 2:1 Brij 97 and 1-butanol by different experimental techniques. A pseudoternary phase diagram was constructed using water titration method. At 45% wt/wt surfactant system, microemulsions containing various ratios of water and IPP were prepared and identified by electrical conductivity, viscosity, differential scanning calorimetry (DSC), cryo-field emission scanning electron microscopy (cryo-FESEM) and nuclear magnetic resonance (NMR). The results from conductivity and viscosity suggested a percolation transition from water-in-oil (water/oil) to oil-in-water (oil/water) microemulsions at 30% wt/wt water. From DSC results, the exothermic peak of water and the endothermic peak of IPP indicated that the transition of water/oil to oil/water microemulsions occurred at 30% wt/wt water. Cryo-FESEM photomicrographs revealed globular structures of microemulsions at higher than 15% wt/wt water. In addition, self-diffusion coefficients determined by NMR reflected that the diffusability of water increased at higher than 35% wt/wt water, while that of IPP was in reverse. Therefore, the results from all techniques are in good agreement and indicate that the water/oil and oil/water transition point occurred in the range of 30% to 35% wt/wt water.

Comparative study of the fluid dynamics of bottom spray fluid bed coaters

Fluid dynamics of pellets processed in bottom spray traditional Wurster coating and swirl accelerated air (precision) coating were compared with the intent to understand and facilitate improvements in the coating processes. Fluid dynamics was described by pellet mass flow rate (MFR) obtained using a pellet collection system and images captured using high speed photography. Pellet flow within the partition column was found to be denser and slower in Wurster coating than in precision coating, suggesting a higher tendency of agglomeration during the coating process. The influence of partition gap and load on the MFR indicated that the mechanism of transport of pellets into the coating zone in precision coating depended on a strong suction, whereas in Wurster coating, pellets were transported by a combination of peripheral fluidization, gravity, and weak suction pressure. In precision coating, MFR was found to increase uniformly with air flow rate and atomizing pressure, whereas MFR in Wurster coating did not correlate as well with air flow rate and atomizing pressure. This demonstration showed that transport in precision coating was air dominated. In conclusion, fluid dynamics in precision coating was found to be air dominated and dependent on pressure differential, thus it is more responsive to changes in operational variables than Wurster coating.

Investigation of Wetting Behavior of Nonaqueous Ethylcellulose Gel Matrices Using Dynamic Contact Angle

PURPOSE

This study reports the development of a method based on dynamic contact angle to investigate the wetting behavior of non-aqueous ethylcellulose (EC) gel matrices intended for topical drug delivery.

METHODS

Non-aqueous gel matrices were prepared from the three fine particle grades of EC and propylene glycol dicaprylate/dicaprate. Dynamic contact angle measurements of sessile drops of water and isopropylmyristate (IPM) on EC gel matrices were performed using a dynamic contact angle analyzer equipped with axisymmetric drop shape analysis of the sessile drop images. Gel density was determined by weighing known volumes of gel samples.

RESULTS

The EC gel matrices were wetted by both water and IPM, with much higher wettability by the latter. Increased EC concentration and polymeric chain length decreased the extent and rate of wetting. Linear correlation was observed between wetting parameters and rheological as well as mechanical properties of EC gel matrices.

CONCLUSIONS

The EC gel matrices exhibited both hydrophilic and lipophilic properties, with predominance of the latter. The extent and rate of wetting was governed by a balance of chemical and physical characteristics of the gel. EC gel matrices showed desirable wetting behavior in their function as a moisture-barrier, bioadhesive and vehicle for topical drug delivery.

Influence of partially cross-linked alginate used in the production of alginate microspheres by emulsification

Spherical and discrete calcium alginate microspheres had been produced by the emulsification technique. The microencapsulation process was highly efficient, but drug release from microspheres was rapid. A more orderly chain arrangement of the polymeric chains would give rise to a stronger and less permeable matrix capable of sustaining drug release. Therefore, the potential of using partially cross-linked alginate in the production of microspheres by emulsification was explored. The size and roundness of the microspheres, its drug content and drug release property were determined. The more viscous alginate solutions when reacted with more calcium salt added resulted in larger microspheres produced. Microspheres made from partially cross-linked alginate exhibited lower drug content and higher T75% values in drug release studies. This was due to decreased flexibility of the polymer chains which were partially held together by calcium ions, reducing subsequent interaction with the calcium ions resulting in lower drug entrapment efficiency and a more permeable microsphere matrix.

Functionality of Cross-Linked Polyvinylpyrrolidone as a Spheronization Aid: A Promising Alternative to Microcrystalline Cellulose

PURPOSE

This work seeks to explore and demonstrate the functionality of cross-linked polyvinylpyrrolidone (crospovidone) as a spheronization aid and a promising alternative to microcrystalline cellulose (MCC).

METHODS

Pellets were prepared with various grades of crospovidone using both small- and large-scale extrusion-spheronization. A Box-Behnken experimental design was employed to elucidate the effects of operating variables on the quality of the pellets. Size and shape analyses of these pellets were conducted and compared to those prepared using MCC.

RESULTS

Crospovidone was believed to behave like a liquid repository in its interaction with water during extrusion-spheronization, although its binding ability was weaker than that of MCC. Spherical pellets of narrow size distribution could be made from the finer crospovidone grades with different lactose grades. However, crospovidone-based formulations required higher water levels than weight-equivalent MCC-based formulations. Crospovidone pellets were of equivalent quality to those prepared with MCC, especially in the shape, size, and yield.

CONCLUSIONS

Crospovidone can be successfully employed as a spheronization aid to produce good pellets without the need of a binder, unlike most of the previously proposed materials. This study exemplified the enormous potential of crospovidone to serve as a competent alternative to MCC in the production of pellets by extrusion-spheronization.

Development of Novel Nonaqueous Ethylcellulose Gel Matrices: Rheological and Mechanical Characterization

PURPOSE

This study reports the rheological and mechanical characterization of novel non-aqueous ethylcellulose gel matrices intended for topical drug delivery. An attempt was also made to explain the molecular interaction within the gel systems from a molecular conformational approach.

METHODS

Nonaqueous gel matrices were prepared from three fine particle grades of ethylcellulose and propylene glycol dicaprylate/dicaprate. Continuous and oscillatory shear rheometry was performed using a cone-and-plate rheometer and mechanical characterization was performed using a universal tensile tester.

RESULTS

The gel matrices exhibited prominent viscoelastic behaviour, yield stress and thixotropy. Rheological and mechanical properties showed significant upward trends with increased polymeric chain length and polymer concentrations. Good linear correlations were obtained between rheological and mechanical properties. The solvent molecular conformation was found to play a role in affecting the formation of gel networks via intermolecular hydrogen bonding between ethylcellulose polymer chains.

CONCLUSIONS

Ethylcellulose was successfully formulated as a nonaqueous gel with propylene glycol dicaprylate/dicaprate. The novel nonaqueous gel exhibited rheological profiles corresponding to a physically cross-linked three dimensional gel network, with suitable mechanical characteristics for use as a vehicle for topical drug delivery. Molecular conformation of the solvent was found to influence the molecular interactions associated with formation of ethylcellulose gel networks.

A Novel Preformulation Tool to Group Microcrystalline Celluloses Using Artificial Neural Network and Data Clustering

PURPOSE

To group microcrystalline celluloses (MCCs) using a combination of artificial neural network (ANN) and data clustering.

METHODS

Radial basis function (RBF) network was used to model the torque measurements of the various MCCs. Output from the RBF network was used to group the MCCs using a data clustering technique known as discrete incremental clustering (DIC). Rheological or torque profiles of various MCCs at different combinations of mixing time and water:MCC ratios were obtained using mixer torque rheometry (MTR). Correlation analysis was performed on the derived torque parameter Torque(max) and physical properties of the MCCs.

RESULTS

Depending on the leniency of the predefined threshold parameters, the 11 MCCs can be assigned into 2 or 3 groups. Grouping results were also able to identify bulk and tapped densities as major factors governing water-MCC interaction. MCCs differed in their water retentive capacities whereby the denser Avicel PH 301 and PH 302 were more sensitive to the added water.

CONCLUSIONS

An objective grouping of MCCs can be achieved with a combination of ANN and DIC. This aids in the preliminary assessment of new or unknown MCCs. Key properties that control the performance of MCCs in their interactions with water can be discovered.

Wet Spheronization by Rotary Processing—A Multistage Single‐Pot Process for Producing Spheroids

Spheronization is an agglomerative size enlargement process for producing spherical agglomerates that have many technological and therapeutical advantages. Rotary processing is an efficient multistage, single-pot spheroid production method. The rotary processor can be used for spheroid production, drying as well as coating. In the course of spheroid production, centrifugal, fluidizing, and gravitational forces act upon the product from different directions and collectively contribute to the spheroid formation process during rotary processing. The outcome of the process depends on the complex interactions between the equipment, formulation, and process variables.

Roller Compaction of Crude Plant Material: Influence of Process Variables, Polyvinylpyrrolidone, and Co‐milling

Roller compaction of a milled botanical (Baphicacanthus cusia) with and without a binder, polyvinylpyrrolidone (PVP) was conducted. Effects of co-milling on binder function and flowability of the powder blend was also investigated. Flakes were comminuted, and the size and size distribution, friability, Hausner ratio, and Carr index of the granulations were determined. Crude herb should be reduced to a suitable size for it to be successfully roller compacted. Larger-sized and less friable granules were obtained with decreasing roller speed. Addition of PVP affected the flowability and binding capacity of the herbal powder blend, which influenced size and friability of the granules. Co-milling of PVP with the herbal powder enhanced the flow of the blends and the effectiveness of the binder, which contributed favorably to the roller-compacted product. Roller compaction is a convenient and cost-effective granulating technique suitable for milled botanicals. Co-milling can be used to improve the properties of roller-compacted products.

Complexation Between PVP and Gantrez Polymer and Its Effect on Release and Bioadhesive Properties of the Composite PVP/Gantrez Films

Complexation between poly(methyl vinyl ether-maleic anhydride) copolymer (Gantrez AN 169) and polyvinylpyrrolidone (PVP K-90D) in aqueous solutions were investigated using a viscometric method and Raman spectroscopy. The composite films with different weight ratios of PVP to Gantrez were prepared in the presence of N-methyl-2-pyrrolidone. The release profiles of diclofenac sodium (DS) from these films were determined and the bioadhesive properties measured. An interpolymer complex was formed through hydrogen bonding between the carbonyl groups of PVP and the hydroxyl groups of Gantrez. The formation of interpolymer hydrogen bonds reduced the interaction of the polymers with water molecules, thus resulting in a lower solubility of the complex in water and a further retarded release of DS from the composite films. The interpolymer complexation was also found to increase the bioadhesive properties of the composite films to a silicone elastomer substrate. The complexation of PVP and the Gantrez copolymer in the composite films was a critical factor affecting the release of DS from the films and the bioadhesive properties of the films.

Use of a Fluidized Bed Hammer Mill for Size Reduction and Classification: Effects of Process Variables and Starting Materials on the Particle Size Distribution of Milled Lactose Batches

The process capability of a fluidized bed hammer mill was investigated with respect to four process variables, namely, rotational speeds of beater system and classifier wheel, airflow rates and length of grinding zones, as well as the particle size and flow property of the starting materials. The size distributions of all the milled lactose batches could be fitted to the Rosin Rammler distribution (RRD) function. The characteristic particle size (De) and uniform coefficient (n), which were derived from the RRD function, complemented the size at the 99th percentile of the cumulative undersize distribution (D99) to characterize the lactose batches. Lower De and D99 values indicate a finer powder while a higher n value indicates a narrower size distribution. The beater speed played a critical role. Increasing the beater speed from 12000 to 21000 rpm generally resulted in an increase in n and a decrease in D99 values due to the greater amount of milling energy supplied. The particle size and flow property of the starting material also played an important role at beater speed of 12000 rpm, where the lowest amount of milling energy was supplied. When a higher amount of milling energy was provided, the effect of particle size of the starting material was less significant. The other process variables exerted varying effects. Increasing the classifier wheel speed from 5000 to 15000 rpm decreased the De and D99 and increased the n values of the milled lactose batches, provided sufficient milling energy was supplied to the lactose particles. Changing airflow rates from 80 to 90 m3/h generally resulted in larger De and D99 values and lower n values as the higher airflow rate provided greater airflow-induced kinetic energy that facilitated the passage of lactose through the classifier wheel. However, changing the long grinding zone to a short one did not significantly affect the De, D99 and n values of the milled lactose batches produced. Small lactose particles of narrow size distribution could be obtained using the fluidized bed hammer mill upon gaining a better understanding of the milling process.

Influence of storage conditions and type of plasticizers on ethylcellulose and acrylate films formed from aqueous dispersions

PURPOSE

To investigate the influence of storage conditions and types of plasticizers on the properties and stability of ethylcellulose and polymethacrylate films and to elucidate the mechanism for the changes observed.

METHODS

Films were prepared from Surelease, Aquacoat and Eudragit L 30D dispersions by the casting method. The effects of different plasticizers on the morphology, transparency, mechanical property and water vapour permeability of the prepared films were studied. The film samples were exposed to storage conditions of 30 degrees C and 50 or 75 %RH. Samples were removed at pre-determined time intervals for mechanical testing and analysis of plasticizer content in the films.

RESULTS

It was found that films prepared from aqueous ethylcellulose dispersions were relatively weaker and more brittle than acrylate films. Acrylate films did not show any significant change in mechanical property when stored at high humidity. However, the properties of ethylcellulose films stored at high humidity varied depending on the type of plasticizers present.

CONCLUSIONS

The changes in mechanical property of ethylcellulose films on storage were mainly attributed to the loss of plasticizers during storage, causing further coalescence of ethylcellulose films and to a smaller extent, reduction in moisture content of the film.