Influence of processing and curing conditions on beads coated with an aqueous dispersion of cellulose acetate phthalate

Eudragit RL-based film coatings: How to minimize sticking and adjust drug release using MAS

Polymeric film coatings based on quaternary polymethacrylates (QPMs, e.g. Eudragits®) are frequently used for controlled release applications. However, their considerable sticking tendency is a major drawback in practice. In this study, different amounts of magnesium aluminum silicate (MAS) were added to the film coatings in order to overcome this hurdle. MAS is negatively charged and can electrostatically interact with the positively charged QPM. Different types of tablet cores were coated with aqueous Eudragit® RL 30D dispersions, optionally containing varying amounts of MAS. Dynamic changes in the wet mass of the systems as well as drug release upon exposure to 0.1 M HCl and phosphate buffer pH 6.8 were monitored. Propranolol HCl, acetaminophen, and diclofenac sodium were used as cationic, nonionic and anionic model drugs. The tablets were optionally cured for 12 h at 45 or 60 °C. Importantly, the addition of MAS to aqueous Eudragit® RL 30D dispersion substantially reduced the films' stickiness and led to stable inner coating structures, even without curing. Desired drug release rates can be adjusted by varying the QPM:MAS ratio and coating level.

Water-insoluble polymers as binders for pellet drug layering: Effect on drug release and performance upon compression

The objective of this study was to investigate the applicability of water-insoluble polymers as binders for pellet drug layering to extend the drug release. Carbamazepine was layered on sugar cores in fluidized bed coater using isopropanol (IPA):water solution or aqueous dispersion of ethylcellulose, polyvinyl acetate or ammonium-methylmethacrylate copolymer. Carbamazepine release was extended with all investigated water-insoluble polymers used as binder, without an additional coating layer. Drug release from pellets layered using IPA:water polymer solutions was dependent on polymer properties such as lipophilicity and pore-forming components, while from those layered with aqueous polymer dispersions, the release was dependent on the completeness of film formation during drug layering. Curing effect was observed only for pellets layered with Aquacoat® ECD and Eudragit® RS 30D. The drug release was not affected by compression when pellets were prepared with the flexible polymers Kollidon® SR or Kollicoat® SR 30D, however, it increased when brittle polymers such as ethylcellulose or Eudragit® RS were used. This problem could be minimized by using a higher amount of the binder, addition of a plasticizer or using polymers of higher viscosity grade. In conclusion, the use of water-insoluble polymers as binder for pellet drug layering is an effective tool to extend the drug release without additional coating step.

Building Process Understanding of Fluid Bed Taste Mask Coating of Microspheres

Taste is routinely cited as one of the major contributing factors that negatively influence pediatric patient compliance. A promising solution is coated microsphere systems, which provide doses of active pharmaceutical ingredients (API) subdivided into a plurality of small dosage units. In this work, the microspheres were coated with Kollicoat® Smartseal, a reverse enteric polymer, which acts to minimize or prevent the release of API in the neutral pH of the oral cavity, which results in a masking effect of the unpleasant taste of the API. A screening of seven key variables in a Wurster coating process was evaluated by D-optimal design and by analysis of variance. The percentage of API released at pH 6.2 was used as a surrogate method for the taste-masking performance evaluation of Kollicoat® Smartseal. The seven studied variables were: product bed temperature, inlet airflow, atomizing air pressure, spray rate (process parameters), coating level, plasticizer level, solids in coating suspension (material attributes), and curing. Results show that coating level, plasticizer level, product bed temperature, and spray rate are the critical process parameters and reinforce the importance of curing to reduce the overall variability within the batch by promoting complete film formation. The link between material attributes, process parameters, and quality attributes were demonstrated to allow a better understanding of the parameters that affect the API release profile at neutral pH (in vitro) while not injuring release at acidic pH (in vitro). It was demonstrated that not only thickness but also coating morphology have an impact on the dissolution in 50 mM potassium phosphate buffer, pH 6.2.

pH-responsive CAP-co-poly(methacrylic acid)-based hydrogel as an efficient platform for controlled gastrointestinal delivery: fabrication, characterization, in vitro and in vivo toxicity evaluation

Cellulose acetate phthalate-based pH-responsive hydrogel was synthesized for fabrication of polymeric matrix tablets for gastro-protective delivery of loxoprofen sodium. Cellulose acetate phthalate (CAP) was cross-linked with methacrylic acid (MAA) using free radical polymerization technique. Fourier transform infrared (FTIR) spectra confirmed the formation of cross-linked structure of CAP-co-poly(methacrylic acid). Thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) confirmed the thermal stability of polymeric networks, and scanning electron microscopy (SEM) and energy-dispersive X-ray spectrum (EDS) images unveiled that the prepared formulations were porous in nature and thus the developed formulations had shown better diffusibility. Swelling and in vitro drug release was performed at various pHs and maximum swelling and release was obtained at pH 7.4, while swelling and release rate was very low at pH 1.2 which confirmed the pH-responsive behavior of CAP-co-poly(MAA). CAP-co-poly(MAA) copolymer prevents the release of loxoprofen sodium into the stomach due to reduced swelling at gastric pH while showing significant swelling and drug release in the colon. Cytotoxicity studies revealed higher biocompatibility of fabricated hydrogel. Acute oral toxicity studies were performed for the evaluation and preliminary screening of safety profile of the developed hydrogels. Matrix tablets were evaluated for release behavior at simulated body pH. The investigations performed for analysis of hydrogels and fabricated matrix tablets indicated the controlled drug release and gastro-protective drug delivery of CAP-co-poly(MAA) hydrogels and pH-sensitive matrix tablets for targeted delivery of gastro-sensitive/irritative agents. Graphical abstract.

Soft Gelatin Films Modified with Cellulose Acetate Phthalate Pseudolatex Dispersion-Structure and Permeability

Gastroresistant material, based on gelatin and intended to form capsule shells, was characterized. The films were obtained by mixing a gelatin solution with cellulose acetate phthalate (CAP) pseudolatex at an elevated temperature. Microscopic and spectroscopic analyses of the films—intact or subjected to the acidic treatment—were performed, along with a permeability study of tritium-labeled water. A uniform porous structure formed by CAP within the gelatin gel was observed. The results demonstrated that no interaction of a chemical nature occurred between the components. Additionally, the performed permeability and solubility studies proved that the diffusion of water through the membranes at an acidic pH can be noticeably reduced by adding carrageenan as a secondary gelling/thickening agent.

A Systematic Approach of Employing Quality by Design Principles: Risk Assessment and Design of Experiments to Demonstrate Process Understanding and Identify the Critical Process Parameters for Coating of the Ethylcellulose Pseudolatex Dispersion Using Non-Conventional Fluid Bed Process

The goal of this study was to utilize risk assessment techniques and statistical design of experiments (DoE) to gain process understanding and to identify critical process parameters for the manufacture of controlled release multiparticulate beads using a novel disk-jet fluid bed technology. The material attributes and process parameters were systematically assessed using the Ishikawa fish bone diagram and failure mode and effect analysis (FMEA) risk assessment methods. The high risk attributes identified by the FMEA analysis were further explored using resolution V fractional factorial design. To gain an understanding of the processing parameters, a resolution V fractional factorial study was conducted. Using knowledge gained from the resolution V study, a resolution IV fractional factorial study was conducted; the purpose of this IV study was to identify the critical process parameters (CPP) that impact the critical quality attributes and understand the influence of these parameters on film formation. For both studies, the microclimate, atomization pressure, inlet air volume, product temperature (during spraying and curing), curing time, and percent solids in the coating solutions were studied. The responses evaluated were percent agglomeration, percent fines, percent yield, bead aspect ratio, median particle size diameter (d50), assay, and drug release rate. Pyrobuttons® were used to record real-time temperature and humidity changes in the fluid bed. The risk assessment methods and process analytical tools helped to understand the novel disk-jet technology and to systematically develop models of the coating process parameters like process efficiency and the extent of curing during the coating process.

Curing mechanism of flexible aqueous polymeric coatings

The objective of this study was to explain curing phenomena for pellets coated with a flexible polymeric coating based on poly(vinyl acetate) (Kollicoat® SR 30D) with regard to the effect of starter cores, thickness of drug layer, adhesion of coating to drug-layered-cores as well as coating properties. In addition, appropriate approaches to eliminate the curing effect were identified. Sugar or MCC cores were layered with the model drugs carbamazepine, theophylline, propranolol HCl, tramadol HCl and metoprolol HCl using HPMC (5 or 25% w/w, based on drug) as a binder. Drug-layered pellets were coated with Kollicoat® SR 30D in a fluidized bed coater using TEC (10% w/w) as plasticizer and talc (35-100% w/w) as anti-tacking agent. Drug release, pellet properties (morphology, water uptake-weight loss and osmolality) and adhesion of the coating to the drug layer were investigated as a function of curing at 60°C or 60°C/75% RH for 24h. The film formation of the aqueous dispersion of Kollicoat® SR 30D was complete, and therefore, a strong curing effect (decrease in drug release) at elevated temperature and humidity (60°C/75% RH) could not be explained by the well-known hydroplasticization and the further gradual coalescence of the colloidal polymer particles. According to the provided mechanistic explanation, the observed curing effect was associated with (1) high flexibility of coating, (2) adhesion between coating and drug layer, (3) water retaining properties of the drug layer, and (4) osmotically active cores. Unwanted curing effects could be minimized/eliminated by the addition of talc or/and pore-forming water soluble polymers in the coating, increasing binder amount or applying an intermediate coating, by increasing the thickness of drug layer or using non-osmotic cores. A new insight into curing phenomena mainly associated with the adhesion between drug layer and coating was provided. Appropriate approaches to avoid unwanted curing effect were identified.

Applicability of near-infrared spectroscopy in the monitoring of film coating and curing process of the prolonged release coated pellets

Although process analytical technology (PAT) guidance has been introduced to the pharmaceutical industry just a decade ago, this innovative approach has already become an important part of efficient pharmaceutical development, manufacturing, and quality assurance. PAT tools are especially important in technologically complex operations which require strict control of critical process parameters and have significant effect on final product quality. Manufacturing of prolonged release film coated pellets is definitely one of such processes. The aim of the present work was to study the applicability of the at-line near-infrared spectroscopy (NIR) approach in the monitoring of pellet film coating and curing steps. Film coated pellets were manufactured by coating the active ingredient containing pellets with film coating based on polymethacrylate polymers (Eudragit® RS/RL). The NIR proved as a useful tool for the monitoring of the curing process since it was able to determine the extent of the curing and hence predict drug release rate by using partial least square (PLS) model. However, such approach also showed a number of limitations, such as low reliability and high susceptibility to pellet moisture content, and was thus not able to predict drug release from pellets with high moisture content. On the other hand, the at-line NIR was capable to predict the thickness of Eudragit® RS/RL film coating in a wide range (up to 40μm) with good accuracy even in the pellets with high moisture content. To sum up, high applicability of the at-line NIR in the monitoring of the prolonged release pellets production was demonstrated in the present study. The present findings may contribute to more efficient and reliable PAT solutions in the manufacturing of prolonged release dosage forms.

Development of a gel permeation chromatographic assay to achieve mass balance in cellulose acetate phthalate stability studies

Cellulose acetate phthalate (CAP, cellulose acetate 1,2-benzenedicarboxylate) is a common polymeric oral tablet coating. CAP is also a vaginal microbicide candidate that potently inhibits HIV-1 proliferation. This paper describes the development of a precise, stability-indicating gel permeation chromatography (GPC) assay for CAP. During accelerated stability studies monitored by separate reversed-phase high performance liquid chromatography (RP-HPLC) and GPC analyses, an apparent loss of mass balance was observed. This deficit was corrected by recalculating the response factor (RF) for each degraded sample, proportional to the fraction of phthalate remaining bound to the polymeric CAP. The correction factor enabled CAP and the degradation product phthalic acid (PA) to be quantitated by a single GPC analysis. The chromatographic approach taken here could potentially apply to any polymer containing degradable chromophores.

Effect of Neutralization of Poly(Methacrylic Acid-co-ethyl Acrylate) on Drug Release From Enteric-coated Pellets Upon Accelerated Storage

The effect of neutralization of poly(methacrylic acid-co-ethyl acrylate) or poly(MA-EA) 1:1 (Eudragit L 30 D-55) on drug release from enteric-coated pellets was studied upon accelerated storage. The dissolution rate of un-neutralized poly(MA-EA)-coated pellets decreased while the neutralized polymer-coated pellets maintained a constant drug release rate. Dynamic mechanical analysis showed that both un-neutralized and neutralized poly(MA-EA) films became rigid on aging. However, the un-neutralized films were affected more than those neutralized. Neutralization of poly(MA-EA) significantly changed the mechanical properties of coating films and improved the stability of poly(MA-EA) enteric-coated pellets upon accelerated storage at the studied conditions.

Aqueous HPMCAS coatings: Effects of formulation and processing parameters on drug release and mass transport mechanisms

The major aim of the present work was to study the effects of various formulation and processing parameters on the resulting drug release kinetics from theophylline matrix pellets coated with aqueous hydroxypropyl methylcellulose acetate succinate (HPMCAS) dispersions. The plasticizer content, coating level and curing conditions significantly affected the release patterns in 0.1 M HCl, whereas no major effects were observed in phosphate buffer, pH 7.4. Due to the significant size of the HPMCAS particles (being in the micrometer range), their coalescence was particularly crucial and not complete upon coating. Consequently, at low coating levels continuous water-filled channels connected the bead cores with the release medium through which the drug could rapidly diffuse, resulting in high release rates even at low pH. In contrast, at high coating levels such continuous connections did not exist (due to the increased number of polymer particle layers), and drug release was controlled by diffusion through the macromolecular network resulting in much lower release rates in 0.1 M HCl. Importantly, pellet curing at elevated temperature and ambient relative humidity or exposure to elevated relative humidity at room temperature did not significantly alter the microstructure of the coatings, leading to only slightly decreased drug release rates. In contrast, pellet curing at elevated temperature combined with elevated relative humidity induced significant further polymer particle coalescence, resulting in a change of the underlying drug release mechanism and significantly reduced drug release rates.

Development of a simple method for the preparation of a silica gel based controlled delivery system with a high drug content

Silica gel was used as core particles to design a simple preparation for controlled delivery system with a high drug content. Drug loading was carried out by immersing the silica gel in a pre-heated drug solution or suspension. HPLC, SEM, DSC, PXRD analysis and N2 adsorption studies evaluated the drug-loading process. In the next step, the drug-loaded silica gel was coated with hydroxypropyl methylcellulose (HPMC) and an aqueous dispersion of ethylcellulose (Aquacoat) to control the drug release. The release profile was determined using a dissolution test. The results showed that silica gel could adsorb great quantities of the drug, up to about 450 mg/g, by repetition of the loading process. Evaluation of the drug-loading process indicates that drug deposition in the pores occurs during the loading process and the drug-loading efficacy is strongly related to the drug solubility. On the other hand, the dissolution test showed that the drug release could be controlled by polymer coating the drug-loaded silica gel. An HPMC undercoating effectively suppresses the drug release, as it smoothes the drug-loaded core surface and aids in the formation of a continuous Aquacoat coating film. The floating property was also observed during the dissolution test.

Cellulose acetate butyrate microcapsules containing dextran ion-exchange resins as self-propelled drug release system

Sulfopropylated dextran microspheres (SP-Ms), (Dm = 80 microm) loaded with a water soluble drug (Tetracycline HCl), were included in cellulose acetate butyrate (CAB) microcapsules. Spherical CAB microcapsules were obtained by oil in water (o/w) solvent evaporation method in the presence of an inert solvent as cyclohexane (CyH) or n-hexane (N-Hex), and different excipients (Phospholipon, Tween, Span, Eudragit RS 100). Chloroform was found to be the best solvent for the preparation of the microcapsules. Also, the sphericity as well as the porosity of the microcapsules was controlled by the presence of an inert solvent. The final concentration of the drug in CAB microparticles was up to 25% (w/w). The key factors for the successful preparation were also the viscosity of the polymer, while the wettability of the resulted microcapsules, the temperature of the preparation, and the porosity have modulated the release of the drug. The higher is the amount of encapsulated microspheres the thinner is the CAB wall between the compartments created by their incorporation. When these microspheres come in contact with the release medium, the pressure created by their swelling breaks the polymer film and the drug starts to be released. The more drug is released in phosphate buffer the higher is the swelling degree of the encapsulated ion exchange resins and the force created by their supplementary swelling will break the more resistants walls. In this way a self-propelled drug release is achieved, until almost all drug was eliberated.

Coating of pellets with micronized ethylcellulose particles by a dry powder coating technique

Pellets were coated with ethylcellulose powder to achieve extended release. The film forming ability of ethylcellulose powder and the effect of formulation factors (plasticizer type and concentration) and curing conditions (curing temperature and time) were investigated. The coating formulation was divided into two components consisting of a powder mixture (polymer plus talc) and a mixture of liquid materials (plasticizer plus binder solution), which were sprayed separately into the coating chamber of a fluidized bed coater (Glatt GPCG-1, Wurster insert). The coated pellets were oven-cured under different conditions (60-80 degrees C, 2-24 h) without and with humidity (100% relative humidity). Propranolol hydrochloride was used as a model drug, and drug release was studied in 0.1 N HCl at 37 degrees C (USP XXV paddle method). Despite the high glass transition temperature of ethylcellulose (133.4 degrees C), micronized ethylcellulose powder can be used for dry powder coating by adjusting the coating temperature, amount and type of plasticizer applied, and curing conditions. 40% plasticizer and a curing step (80 degrees C, 24 h) were required to achieve complete coalescence of the polymer particles and extended drug release of coated pellets. Although ethylcellulose-coated pellets had an uneven surface, extended drug release could be obtained with coating level of 15%. Because of its high glass transition temperature, ethylcellulose-coated pellets showed unchanged drug release profiles upon storage at room temperature for 3 years.

Effect of Curing Conditions and Plasticizer Level on the Release of Highly Lipophilic Drug from Coated Multiparticulate Drug Delivery System

The study aimed to investigate the effect of triethyl citrate (TEC) plasticizer level (10, 15, and 20%), curing temperature (40, 50, and 60 degrees C) and time (0 to 168 h) on the release of a highly lipophilic drug bumetanide from pellets coated with methacrylate ester copolymer (Eudragit RS). Bumetanide was layered onto sugar pellets followed by coating with 6% Eudragit RS with and without hydroxypropyl methyl cellulose (HPMC) seal coat using Wurster Fluid Bed equipment. Coated pellets were stored for 3 months at room temperature and the release was tested in USP purified water. At 10% TEC level, increasing curing time and temperature lead to slower drug release. At 15 and 20% TEC levels, curing initially decreased drug release followed by increase in the release at longer curing time and higher temperature. Drug release from coated pellets plasticized with 15% TEC and completely cured followed zero order kinetic models. At plasticizer level of 20%, bumetanide release from the completely cured pellets was better modeled using the Higuchi's equation reflecting possible drug migration during curing. Storage led to an increase in drug release. The use of HPMC seal coat stabilized drug release after storage. It was concluded that bumetanide migration into Eudragit RS film coat was the main cause of the accelerated release after curing and storage. The drug migration during storage at room temperature was prevented by seal coating the pellets with HPMC.

Properties of heat-humidity cured cellulose acetate phthalate free films

Cellulose acetate phthalate (CAP) free films containing diethyl phthalate (DEP) or triethyl citrate (TEC) as the plasticizer were prepared by the spray method. The chemical and mechanical properties of films were compared following heat-only (50 degrees C for 24 h) and heat-humidity curing (50 degrees C/75% RH for 24 h) conditions. The surface roughness of the heat-humidity cured films decreased compared to that of the uncured and heat-only cured films. The heat-humidity curing condition suppressed evaporation of the plasticizer, resulting in higher plasticizer levels remaining in the films, as compared to the heat-only curing condition. The heat-humidity curing also significantly increased the mechanical strength and decreased the water vapor permeability of the films. When exposed to the acidic media, despite rapid leaching of plasticizer, the heat-humidity cured films retained the most mechanical strength of the films prior to exposure. The moisture content and phthalic acid content after heat-humidity curing were increased slightly, but did not reach a level that would interfere with enteric performance. TEC was less volatile and produced films with increased % elongation, and decreased tensile strength and elastic modulus compared to the films plasticized with DEP. However, the DEP plasticized films were less permeable than TEC-plasticized films following heat-humidity curing. The results indicated that a short-term exposure of the CAP films to heat and humidity during the curing process greatly improved the degree of film coalescence and mechanical strength, without causing significant chemical degradation of the polymer.

Long-term stability of heat-humidity cured cellulose acetate phthalate coated beads

The objective of this study was to investigate the influence of stability storage conditions on the enteric release of heat-humidity cured cellulose acetate phthalate (CAP) coated beads. Theophylline beads were coated with 25 or 35% diethyl phthalate plasticized CAP dispersion (Aquacoat CPD), and cured at a heat-humidity condition (50 degrees C/75% RH) for 24h. The cured beads were then stored in various container/closure systems (open glass containers, sealed glass containers with and without desiccant) and exposed to 40 degrees C/75% RH for 6 months or 25 degrees C/60% RH for 12 months. At accelerated conditions (40 degrees C/75% RH), only beads stored in sealed glass containers with desiccant displayed stable release profiles throughout the exposure period. The beads stored in sealed glass containers without desiccant showed increased theophylline release in acidic media at 2h, and did not maintain enteric resistance at 6 months. The release profiles of beads stored in open containers, directly exposed to 40 degrees C/75% RH, were the least stable. The decrease in enteric protection of the beads stored at these two packaging conditions was correlated to an increased phthalic acid content in the films. At ambient storage conditions (25 degrees C/60% RH), all samples possessed enteric release properties, irrespective of the container/closure system. Beads stored in sealed glass containers with desiccant remained the most stable compared to those at the other two packaging conditions. The results indicated that although humidity significantly contributed to coalescence of CAP coating during the curing process, the optimum packaging condition for the heat-humidity cured CAP coated beads was with desiccant to maintain the chemical stability of the CAP.

The influence of plasticizer on heat-humidity curing of cellulose acetate phthalate coated beads

The objectives of the present study are to investigate the effect of plasticizer type and level on the curing of cellulose acetate phthalate (CAP) coated beads with and without the presence of humidity. Theophylline beads were coated in a fluidized-bed with CAP dispersion (Aquacoat CPD) plasticized by a water-insoluble plasticizer, diethyl phthalate (DEP), or a water-soluble plasticizer, triethyl citrate (TEC), at various levels. The coated heads were cured at a heat-only condition (50 degrees C for 24 hr) and a heat-humidity condition (50 degrees C/75% RH for 24 hr). Rapid drug release in the acidic media was found for both heat-only and heat-humidity cured beads when plasticizer was not used in the coating dispersion, indicating that the heat-humidity curing is ineffective without the presence of plasticizers. When plasticizer was incorporated in the coating formulations, heat-humidity curing effectively improved the acid resistance of the coated films at all plasticizer levels investigated. The minimum plasticizer level required to obtain enteric release profiles for heat-humidity cured beads coated at an outlet coating temperature of 46 degrees C was 15%. This limit was further decreased when the beads were coated at a lower temperature due to a less plasticizer loss at the lower coating temperature. Between the two plasticizers, less TEC was lost during the coating process, and TEC was more effective compared to DEP with regards to heat-humidity curing at the 10% plasticizer level. The enteric release profiles were reproducible following a 7-day drying period at 40 degrees C for all heat-humidity cured beads that had initially passed the enteric release dissolution test. The rapid leaching of TEC and DEP into the.