Article

Novel low-molecular-weight hypromellose polymeric films for aqueous film coating applications

Taylor & Francis
Drug Development and Industrial Pharmacy
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Abstract

The concentration of hypromellose (HPMC) is known to significantly impact the viscosity of coating solutions. The purpose of this study was to determine the viscosity of novel low-molecular-weight (LMW) HPMC products as a function of polymer concentration. The mechanical properties and water vapor permeability of free films prepared from these novel LMW HPMC polymers were also determined and the results were compared with films prepared with conventional HPMC. Solutions of LMW and conventional HPMC 2910 and 2906 containing up to 40% polyethylene glycol (PEG) 400 were prepared and the viscosities were measured using a Brookfield viscometer. Solutions were then cast onto glass plates and stored at 30?C and 50% relative humidity until films were formed. A Chatillon digital force gauge attached to a motorized test stand was used to quantify the mechanical properties of the films, whereas water vapor permeabilities were determined according to the ASTM E96 M-05 water method. As expected, the novel LMW polymer solutions exhibited significantly lower viscosities than the conventional comparators at equivalent polymer concentrations. Film strength of the LMW materials was lower than films prepared from the conventional HPMC solutions, although this effect was not as evident for the HPMC 2906 chemistry. Increasing concentrations of the plasticizer resulted in decreased tensile strength and Young?s modulus and increased elongation as well as increased water vapor permeability, irrespective of polymer type. No statistical difference was found between the tensile strength to Young?s modulus ratios of the F chemistry LMW and conventional HPMC polymer films.

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... In case of the investigated MOBS 3P4 and 6P4 grades, the methoxyl content is 29% and hydroxypropyl content is 8.9% [26]. Pharmaceutical literature describes HPMC as chemically inert and having excellent film-forming properties [25,[27][28][29][30][31][32]. HPMC is produced with a broad viscosity range: from 2.4 mPa·s to 200.000 mPa·s (at 2% 20 °C) [30][31][32][33]. ...
... Pharmaceutical literature describes HPMC as chemically inert and having excellent film-forming properties [25,[27][28][29][30][31][32]. HPMC is produced with a broad viscosity range: from 2.4 mPa·s to 200.000 mPa·s (at 2% 20 °C) [30][31][32][33]. The high viscosity grade HPMC has been mentioned by Feller [5], but ultra-low viscosity grade HPMC has not been previously reported in conservation literature. ...
... In case of the investigated MOBS 3P4 and 6P4 grades, the methoxyl content is 29% and hydroxypropyl content is 8.9% [26]. Pharmaceutical literature describes HPMC as chemically inert and having excellent film-forming properties [25,[27][28][29][30][31][32]. HPMC is produced with a broad viscosity range: from 2.4 mPa·s to 200.000 mPa·s (at 2% 20 • C) [30][31][32][33]. ...
Article
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Paintings and other works of art created with fragile and mechanically unstable powdery me-dia present challenges to conservators. Frequently, powdery media is water-sensitive, extreme-ly fragile, tends to delaminate, and may be altered by even the slightest physical action or in-teraction with liquids. Materials that can provide an efficient stabilization without unaccepta-bly altering the optical characteristics of the delicate substrate are extremely limited. Among these, Funori, Isinglass, and Methocel A4C have become established for this use. In bench prac-tice, consolidants are frequently applied in a non-contact way, using ultrasonic and pneumatic aerosol generators to minimize the impact of the consolidant on sensitive substrates. However, nebulizing the available materials is problematic in bench practice, because of their high vis-cosity and, only extremely low concentrations can be nebulized using low kinetic impact ul-trasonic or pressure-based misting systems adopted from the healthcare industry. As a poten-tial innovative solution, this study introduces novel ultra-low viscosity (ULV) cellulose ethers (ULV-HPMC) for stabilisation of unstable porous and powdery surfaces, which have been suc-cessfully applied in bench practice for the pilot treatment of Edvard Munch painting on canvas and two 19th c. Thai gouache paintings on panel. Novel ULV-HPMC materials have multiple desirable qualities for consolidation treatments in conservation, and in accelerated aging tests marginally outperformed Methocel A4C, considered to be one of the most stable consolidants in the practice of conservation. Because of the ultra-low viscosity, higher concentrations of ULV-HPMC materials can be applied as water-based aerosols in a non-contact way and in few-er applications, which is a significant advantage in the treatment of delicate water-sensitive surfaces. Notably, novel ULV biopolymers are low-cost, derive from sustainable and renewable sources, and do not raise health and environmental concerns. Such novel materials and methods seamlessly resonate with the ICOM-CC’s Melbourne 2014 declaration, EU Green Deal, and the UN’s Sustainable Development goals and show potential for adding new sustainable materials with exceptionally low viscosity to the conservator’s toolbox.
... The 10% TPN films exhibited similar tensile strength to the blank films (Fig. 5A, 0 h), likely due to similar chemical structures shared between the EC and starch backbones as well as PMAA and PS 80 that have good compatibility with EC. The 10% TPN films were slightly more rigid and had 24.7% higher Young's modulus than the blank films (Fig. 5B, 0 h), attributable to higher internal stress in the films [37,38]. In comparison to blank and 10% TPN films, the tensile strength and Young's modulus of 10% Eudragit® L films in dry state were much higher. ...
... Since coated oral dosage forms release drugs in aqueous media after administration, the mechanical properties of polymer coating in wet state are more relevant to its in vivo performance, which requires it to be flexible and resistant to ruptures or cracks [25,37]. Thus the ratio of tensile strength to Young's modulus (σ/E) of wet films is a more accurate metric of the performance of a sustained release coating [38,39]. Depending on the properties of active ingredients and coating substrate as well as the physical dimensions of the formulation, drug release mechanisms can vary significantly. ...
Article
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... The viscosity of HPMC solution increases with the increase of polymer average molecular weight and concentration, at a given temperature. For instance, Bruce and coworkers showed that at 25 • C the viscosity of aqueous solutions of HPMC 2906 and 2910 increased exponentially with the polymer concentration within the concentration range of 10 wt% to 20 wt% (Bruce et al., 2011). ...
Article
Hydroxypropyl methylcellulose (HPMC) is a cellulose ether widely used in drug formulations due to its biocompatibility, uncharged nature, solubility in water and thermoplastic behavior. Particularly for ocular and ophthalmic formulations, HPMC is applied as viscosity enhancer agent in eye drops, gelling agent in injections, and polymeric matrix in films, filaments and inserts. The different therapeutic approaches are necessary due to the complex anatomic structure of the eye. The natural ocular barriers and the low drug permeation into the circulatory system make the drug administration challenging. This review presents the eye anatomy and the usual local routes of drugs administration, which are facilitated by the physicochemical properties of HPMC. The relationship between chemical structure and physicochemical properties of HPMC is displayed. The different types of formulations (local application) including HPMC for ocular drug delivery are discussed with basis on recent literature reports and patents.
... Pharmaceutical literature describes HPMC as chemically inert and having excellent film-forming properties [32,33,34]. HPMC is produced with a broad viscosity range: from 2.4 mPas to 200.000 mPas (at 2% 20° C). [35,36,37]. The high viscosity grade HPMC was mentioned by Feller [38], but ultra-low viscosity grade HPMC was not previously reported in conservation literature. ...
Preprint
Paintings and other artworks created with fragile and mechanically unstable powdery media present challenges to conservators. Frequently, powdery media is water-sensitive, extremely fragile, tends to delaminate, and may be altered by even the slightest physical action and interaction with liquids. Materials that can provide for an efficient consolidation without unacceptably altering the optical characteristics of the paint are extremely limited. Among these, Funori, Isinglass, and Methocel A4C have an established use. Often, they are applied using ultrasonic misting to minimize the mechanical impact. However, nebulizing is problematic because of its high viscosity. This study introduces new ultra-low viscosity (ULV) cellulose ethers (HPMC) materials for consolidation of powdery media, which were applied treating Edvard Munch and two 19th c. Thai gouache paintings. The proposed HPMC materials have multiple desirable qualities for consolidation treatments and, in accelerated aging, by a small margin, outperformed Methocel A4C, which is considered to be among the most stable conservation materials. Novel ULV HPMC materials can be nebulized at higher concentrations, and fewer water-based applications are required, which is a significant advantage in consolidation treatments. Notably, ULV biopolymers are low-cost and from renewable sources, safe for conservators and the environment, which resonates with the ICOM-CC's Melbourne 2014 declaration, EU Green Deal, and U.N.'s Sustainable Development Goals, and is adding new sustainable material to conservator's toolbox.
... Solid content and viscosity: The amount of polymers in the coating solution is important in determining the viscosity of coating solution. The viscosity of coating solution is increased by using a high molecular weight polymer or high polymer content in coating solution [36]. High solid content in coating solution increases tablet weight faster but can lead to difficulty transferring a viscous coating liquid. ...
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Tablet film coating is a common but critical process providing various functionalities to tablets, thereby meeting diverse clinical needs and increasing the value of oral solid dosage forms. Tablet film coating is a technology-driven process and the evolution of coated dosage forms relies on advancements in coating technology, equipment, analytical techniques, and coating materials. Although multiple coating techniques are developed for solvent-based or solvent-free coating processes, each method has advantages and disadvantages that may require continuous technical refinement. In the film coating process, intra- and inter-batch coating uniformity of tablets is critical to ensure the quality of the final product, especially for active film coating containing active pharmaceutical ingredients in the coating layer. In addition to experimental evaluation, computational modeling is also actively pursued to predict the influence of operation parameters on the quality of the final product and optimize process variables of tablet film coating. The concerted efforts of experiments and computational modeling can save time and cost in optimizing the tablet coating process. This review provides a brief overview of tablet film coating technology and modeling approaches with a focus on recent advancements in pharmaceutical applications.
... Functional coating such as modified release, osmotic pressure-controlled drug delivery system, and enteric coatings can be done for advanced drug delivery systems. Film coating process ensures for batch to batch uniformity as well as good reproducibility [3]. Coating formulation majorly contains polymers, plasticizer, anti adherents, surfactants, and colorants. ...
Chapter
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Over a previous couple of decades, polymers are widely used as pharmaceutical excipients in many novel and conventional drug delivery systems from being merely used as gelatin shells to contribute massive formulation benefits such as controlled/sustaining the drug release and also targeting of drugs to the specific site, consequently hold a considerable clinical promise. Currently, numerous dosage forms are provided with diverse coating techniques, which may give out a variety of functions. Based on functionality, several polymer coatings are available commercially to offer incessant formulating choices. In this chapter, recent advancements in the usage of polymers for coating of different dosage forms such as tablets, capsules, implants, nanoparticles, and liposomes, etc., are discussed. Mechanisms of polymeric film formation and applications of polymer coatings in the different areas of biomedicine are clearly explained. Application of different polymers in various coating functions is extensively reported.
... A medida que aumenta la concentración del polímero, la viscosidad también aumenta, esta depende de del peso molecular del polímero. Así pues, la viscosidad de la solucione limita la concentración del polímero en la formación de la película (Bruce et al., 2011). ...
Thesis
Drugs can lose their stability when exposed to environmental factors such as light, moisture or heat. To prevent these degradation reactions, a pharmaceutical coating was formulated from pectin, which is a heteropolysaccharide composed mainly of polygalacturonic acid and is widely used in the pharmaceutical industry as an excipient in the formulation of tablets, coatings and gels. The pectin was extracted from the peel of the fruit Citrus sinensis, following the method of acid hydrolysis. From the extracted pectin, a coating was formulated that was dispersed into tablets of metformin hydrochloride of the Merck brand, which was evaluated through tests established by the Pharmacopoeia of the United Mexican States. It was found that the coating has a high content of phenolic compounds that could exert an antioxidant effect on the active ingredient of the drug. The coating also functions as a protective barrier as it prevents mass loss when the tablets fracture as well as accelerating the disintegration process. Key words: pectin, film coating, tablets.
... Polymeric films are progressively replacing sugar coating since 1954, with the benefits of reducing the time of automated processing and achieving a more uniform coating, in addition to the variety of functions and colors [1][2][3]. Film coatings can provide drugs protection from mechanical stress and moisture, odor and taste masking, modified release profiles, better stability, and lower or abrogated gastrointestinal tract irritation [4]. ...
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... For tablets, polymer film coating is still the most widely used and efficient taste masking technique in the pharmaceutical industry (Ayenew et al., 2009;Joshi and Petereit, 2013;Sohi et al., 2004). In addition to taste masking purposes, polymer film coating of tablets offers a variety of practical advantages that contribute to their therapeutic effect, as well as ensure patient compliance and tablet product stability throughout their shelf life (Bruce et al., 2011;Felton, 2007;Joshi and Petereit, 2013;Pearnchop et al., 2003;Siepmann et al., 2013). With polymer film coating, however, sufficient taste masking and drug release control demand relatively thick polymer films, and consequently, the application of large amounts of polymers (Joshi and Petereit, 2013). ...
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... hydroxypropyl methylcellulose, polyvinyl acetate or polyvinyl pyrrolidone [9]. Different problems may arise during film coating of metronidazole like scuffing, excessive roughness (orange peel), twinning, surface erosion, discoloration, picking and sticking, logo bridging, breakage film, cracking, film peeling, tablet edge chipping erosion and filling of logos/break lines due to non-technical handling of tablets by untrained personnels, use of non-suitable polymers for coating, lack of following the standard operating procedures for film coating, no control on temperature [10], i.e. over drying or over wetting the tablets to be coated [11,12], using high viscous polymers, very sharp tablet edges [13]. So, corrective measures should be taken as a remedy in case of any problem that arises during film coating like to change the tablet's shape, shorten the duration of the film coating process, decrease spray rate [14], make tablet having greater mechanical strength and high flexibility [15] and increase pan speed in the spray zone. ...
Article
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... The widespread use of cellulose ethers as film coating polymers is attributed to their ability to coat using aqueous system that makes them environmental friendly. Moreover, they form a transparent, tough and flexible film that improves the aesthetic appearance of tablets [9][10][11][12][13] . However, difficulties are encountered when the cellulose ethers are introduced into an aqueous medium 14 . ...
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... Polymer films are applied to pharmaceutical solids for cosmetic, protective, or functional purposes (1)(2)(3)(4)(5)(6). The application process is quite complex, with multiple variables related to the substrate characteristics, coating formulation, processing equipment, and processing conditions (7)(8)(9)(10)(11). Figure 1 shows a fishbone diagram of some of the variables that impact film quality and performance in a pan coating process. ...
Article
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... In summary, this paper presents an investigation into several vesicle compositions at different temperatures and pHs, upon addition of pathogenic bacterial agents and within simplified gelling matrixes. The four hydrogel systems that were investigated included the following: gelatin currently used in ophthalmic applications, tissue engineering, and injectable drug delivery; 16 Carbopol 981P NF used in colonic drug delivery; 17 hypromellose used in the coatings of active ingredients; 18 agarose used for injectable protein delivery systems. 19 These were chosen for their biologically favorable pH and established use in applications at biological interfaces. ...
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The authors determined the effects of solvent systems, polyethylene glycol (PEG) molecular weights, and various concentrations of cellulose acetate (CA) to PEG on the thermomechanical properties and permeability of CA-free films.
Article
The effects of polyethylene glycols (PEG 400, 1500 and 4000) used as plasticizer on the moisture permeability and mechanical properties of aqueous hydroxypropyl methylcellulose (HPMC) films were evaluated with free films. The free films were prepared by using a pneumatic spraying technique similar to that used in fluidized-bed coaters. There was a clear relationship between some physical film properties and the molecular weights and concentrations of the PEGs used as plasticizer. Over the range of concentrations tested, the moisture permeability of the films decreased slightly as compared to unplasticized control films with increasing molecular weight of the plasticizer. The mechanical strength of the films was shown to be more dependent on the concentration than on the molecular weight of the PEGs, while the ductility of the films was mainly dependent on the molecular weight of the PEG. The addition of PEG at a concentration of 10% resulted in relatively hard and strong films with a moderate elongation (ductility), especially when lower molecular weight plasticizers (PEG 400 or 1500) were used. As regards permeability to moisture and mechanical properties, the addition of PEG at a concentration in the range of 10–20% of the polymer weight seems to be beneficial for aqueous-based HPMC film coats.
Article
Abstract The aim of this work is to examine the effects that certain plasticisers have on the properties of aqueous based hydroxypropylmethylcellulose (HPMC) films of a type used for film coating tablets, and to investigate whether or not the inclusion of these additives is in fact beneficial in all cases. The film former HPMC is being used increasingly as a coating for pharmaceutical tablets because of its suitable properties, not least of which is the ability to coat using a fully aqueous system. This greatly improves the method and safety of application.
Article
Abstract The effects of plasticizers, triacetin and three different molecular weights of polyethylene glycol, on the water permeation and mechanical properties of cellulose acetate were investigated. At 37°C, the water permeability of cellulose acetate was found to decrease with increasing plasticizer to a minimum and then to increase with higher concentrations of plasticizer. Low plasticizer concentrations caused a decrease in water permeability by antiplasticization. Antiplasticization arose from an interaction between the polymer and the plasticizer molecules and decreases the molecular mobility of the polymer. This effect was confirmed by mechanical measurements of polymer free films at the same experimental temperature. However, when the temperature was raised above the glass transition temperature, Tg, of the polymer films, the polymer films contain enough energy to overcome the interaction between the polymer and plasticizer molecules, and the antiplasticization effect disappeared.
Article
Abstract The effects of plasticizer, polyethylene glycol (PEG-600), on the sucrose permeability, void volume and morphology of cellulose acetate free films were investigated. The sucrose permeability of cellulose acetate free films was found to decrease with increasing PEG-600 to a minimum and increase dramatically when they were plasticized by over 30% (w/w) PEG-600. The decrease in sucrose permeability of cellulose acetate free films with increasing plasticizer at low plasticizer concentrations could be interpreted by the antiplasticization effect, and the dramatic increase of sucrose permeability of cellulose acetate free films at high plasticizer level could be explained by the formation of plasticizer channels. The void volume of cellulose acetate free films were calculated by determining the water content in the films, and the effect of PEG-600 on the morphology of cellulose acetate free films was studied by using the scanning electron microscopy (SEM). Both the void volume and SEM studies supported the assumption that the plasticizer channels would be formed in the polymer films which contain high concentration of plasticizer.
Article
The influence of plasticizers in film coating formulations on the adhesive properties of an acrylic resin copolymer was determined using the butt adhesion technique. Hydrophilic and hydrophobic plasticizing agents were incorporated into aqueous dispersions of Eudragit® L 30 D-55 and coated onto hydrophilic and hydrophobic tablet compacts. Using data obtained from a Chatillon digital force gauge attached to a motorized test stand, force-deflection profiles, similar to stress-strain curves generated in the tensile testing of free films, were constructed and the force of adhesion, elongation at adhesive failure, and adhesive toughness were determined. Plasticizer concentration and plasticizer type were found to influence the adhesive properties of the acrylic polymer. An increase in adhesive toughness was found when the concentration of triethyl citrate (TEC) in the coating formulation was increased from 20 to 30%, which was attributed to an increase in the elasticity of the film and a decrease in the internal stresses within the polymer. Films containing water soluble plasticizers were found to adhere more strongly to the tablet compacts than the water insoluble agents, due to more effective disruption of the intermolecular attractions between the polymer chains. Adhesion of the polymer to tablet compacts was found to be significantly influenced by the hydrophobicity of the tablet surface when the water soluble plasticizers were incorporated into the film coating, whereas no significant differences in the adhesive properties were found when the polymer was plasticized with water insoluble agents. Aging of the film-coated tablets resulted in a decrease in adhesive toughness, irrespective of the environmental storage condition.
Article
Data have been produced on the parameters which influence the development of internal stresses within aqueous HPMC film coats plasticized with glycerol in an attempt to calculate the magnitude of internal stress generation. Films have been prepared under conditions which equate to those experienced during film coating processes. The changes in mechanical and thermal properties of fresh films formed at different tablet bed conditions have been studied during their ambient storage. The contribution of internal stresses from three sources are calculated individually and a single equation is used to estimate the total internal stress within a film. This equation considers the contribution made by the volumetric changes of the tablet core during ambient conditions in addition to those caused by other well-established mechanisms. The results of these calculations showed that the total internal stress is influenced, not only by these volumetric changes, but also by the conditions in which the film coating process was performed. The possibility of the film coating undergoing failure is also discussed.
Article
The enteric coating of soft gelatin capsules (SGC) containing ibuprofen in either PEG 400 or Miglyol© was investigated. The effects of two plasticizers, triethyl citrate (TEC) and tributyl citrate (TBC), on the physical and enteric properties of SGC coated with Eudragit ® L 30 D-55 were studied. The water soluble plasticizer TEC was found to be a good plasticizing agent for the Eudragit® L 30 D-55 irrespective of the fill liquid, while the TBC provided satisfactory results only for capsules containing the hydrophobic fill liquid, Miglyol ®. The combination of TEC and TBC provided effective plasticization for the acrylic coating regardless of the fill liquid. A subcoat of HPMC showed no effect on the enteric protection of either Miglyol® - and PEG-containing capsules that were stored at room temperature and zero percent relative humidity. The moisture content of the gelatin shell of the film coated SGC stored at room temperature and at 0 or 96% relative humidity was followed as a function of time. The load strength of the capsules was measured during 3 months of storage using an Instron universal testing apparatus, and the physical-mechanical properties of the capsules were correlated with the moisture content of the SGC. As the moisture content of the gelatin decreased, all formulations exhibited an increase in load strength.
Article
The use and potential of solubility parameters for pharmaceutical dosage form design are reviewed in this paper. Specific reference is given to the development of the approach, its previous usage and likely future applications. The advantages, assumptions and limitations of this type of approach are also described.
Article
To investigate the physical stability and drug release-related properties of the aqueous polymer dispersions Kollicoat((R)) SR 30 D and Aquacoat((R)) ECD (an ethylcellulose-based dispersion) in the presence water-soluble polymers (pore formers) with special attention to the potential flocculation of the polymer dispersions. A precise characterization of the flocculation phenomena in undiluted samples was monitored with turbidimetric measurements using the Turbiscan Lab-Expert. Theophylline or propranolol HCl drug-layered pellets were coated with Kollicoat((R)) SR 30 D and Aquacoat((R)) ECD by the addition of water-soluble polymers polyvinyl pyrrolidone (Kollidon((R)) 30 and 90 F), polyvinyl alcohol-polyethylene glycol graft copolymer (Kollicoat((R)) IR), and hydroxypropyl methylcellulose (Pharmacoat((R)) 603 or 606) in a fluidized bed coater Glatt GPCG-1 and drug release was performed according to UPS paddle method. Stable dispersions were obtained with both Kollicoat((R)) SR 30 D (a polyvinyl acetate-based dispersion) and Aquacoat((R)) ECD with up to 50% hydrophilic pore formers polyvinyl alcohol-polyethylene glycol graft copolymer (Kollicoat((R)) IR) and polyvinyl pyrrolidone (Kollidon((R)) 30). In general, Kollicoat((R)) SR 30 D was more stable against flocculation than Aquacoat((R)) ECD. Stable dispersions were also obtained with higher amounts of water-soluble polymer or by reducing the concentration of the polymer dispersion. Flocculated dispersions resulted in porous films and, thus, in a sharp increase in drug release. Kollicoat((R)) SR 30 D was more resistant to flocculation upon addition of water-soluble polymers than Aquacoat((R)) ECD. The continuous adjustment of drug release from Kollicoat((R)) SR 30-coated pellets was possible with Kollicoat((R)) IR amounts over a broad range.
Article
Polymeric film coatings have been applied to pharmaceutical solids for decorative, protective, or functional purposes. The application process is quite complex, with variables related to the coating formulation, substrate properties, processing parameters, and interactions thereof, all of which can affect product performance. This article describes a number of experimental techniques used to determine the physical, mechanical, adhesive, thermal, and permeability properties of free and applied films. These analytical tools can be used to optimize product performance, advance our knowledge of the film formation process, and investigate interactions between the coating and the solid surface. Through a better understanding of film-coating processes, the cause of problems that arise during manufacturing, defects observed in the coating, and changes in performance upon subsequent storage may be more quickly and accurately resolved.
Article
Continuous film coating processes are recognized for their high production rates but have had slow acceptance for pharmaceutical production because of perceived high product losses during start-up and shut-down. In this article, the recent improvements in continuous coater designs were evaluated with respect to coating uniformity and reduction in product losses. Two separate studies represent trials conducted in newly redesigned continuous coating pans from two different coating pan manufacturers. Multivitamin tablets were coated with Opadry((R)) II, high performance film coating system, in both batch and continuous modes in the continuous coater. Tablet samples collected throughout all phases of the process were tested for color development and uniformity. Soft gelatin capsules were coated with a delayed release coating formulation, Nutrateric((R)), nutritional enteric coating system. Samples of the soft gelatin capsules were taken throughout the process and tested for resistance to simulated gastric fluid as a measure of coating uniformity and delayed release functionality performance. The results from both the immediate release and delayed release case studies support the assertion that continuous coating processes are capable of applying aqueous film coatings with significant improvements in coating uniformity and reduction in product loss.
Article
Food effects might substantially alter drug release from oral controlled release dosage forms in vivo. The robustness of a novel type of controlled release film coating was investigated using various types of release media and two types of release apparatii. Importantly, none of the investigated conditions had a noteworthy impact on the release of freely water-soluble diltiazem HCl or slightly water-soluble theophylline from pellets coated with ethylcellulose containing small amounts of PVA-PEG graft copolymer. In particular, the presence of significant amounts of fats, carbohydrates, surfactants, bile salts, and calcium ions in the release medium did not alter drug release. Furthermore, changes in the pH and differences in the mechanical stress the dosage forms were exposed to did not affect drug release from the pellets. The investigated film coatings allowing for oral controlled drug delivery are highly robust in vitro and likely to be poorly sensitive to classical food effects in vivo.
Article
The mechanical strength of film-coated tablets has been assessed using the diametral compression test. The results show that the influence of the film is more complex than that suggested by Stern (1976). The film may increase the breaking load of the core itself by acting as a padding material during the test and also by filling in surface irregularities. The film may also have enough intrinsic strength and elasticity to hold the core together once it has broken. The maximum breaking load to completely fracture the coated tablet is related to film properties, but the relation is not a simple one.
Article
Poly(vinyl alcohol) has not previously been examined in much detail as a controlled release polymer for use in pharmaceutical formulations. However, this food grade polymer has barrier and tensile properties which make it attractive for such applications. The effects of several diluents and fillers on Poly(vinyl alcohol) (PVAL) coatings have been determined using both mechanical property and water vapor permeability measurements. It has been found that the alcohol ethoxylate Neodol 23-6.5 (CH3(CH2)11-O-(CH2-CH2-O)6-H) acts as a plasticizer for PVAL only up to 15-20 wt% in contrast to 600 molecular weight Polyethylene Glycol (PEG 600), which continuously plasticizes PVAL. The effects of Neodol on PVAL mechanical properties and water vapor permeability at higher concentrations can be explained in terms of Neodol phase separation and has been confirmed with DSC. The inert filler and whitener titanium dioxide (TiO2) monotonically degrades film mechanical properties and increases water vapor permeability of the coating. Attempts to correlate coating dust generated during particle attrition tests with mechanical property measurements were unsuccessful. A correlation between accelerated granule stability and water vapor permeability of the PVAL coating was established.
Article
The effect of different grades of hydroxyethyl cellulose (HEC) and hydroxypropyl methllcellulose (HPMC) on the film-formation and taste-masking ability for ibuprofen granules was evaluated. Three batches of coated ibuprofen granules were prepared using a roto-granulator, each with a different coating composition. Two grades of HEC [MW300,000 (H) and MW90,000 (L)] were combined with three different grades of HPMC [MW 11,000 (L), MW 25,000 (M) and MW 35,000 (H)] to prepare the coating solutions. Mechanical strength and physical properties of the polymer films were evaluated. Films made from HPMC (L)/HEC (H), HPMC (M)/HEC (H), and HPMC (H)/HEC (H) were stronger and more flexible than the HPMC (L) HEC (L) films. The assay, dissolution, particle size distribution, and environmental scanning electron microscopy (ESEM) data of the three batches of the coated ibuprofen granules were similar.
Article
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.
Article
The effect of triethyl citrate (TEC) and different molecular weights and concentrations of polyethylene glycol (PEG), in addition to the effect of different water-soluble polymers and dispersions at different levels, hydroxypropyl methylcellulose (HPMC), methylcellulose (MC), carbomer 940, polyvinyl alcohol (PVA), ethyl cellulose (EC), on the mechanical and thermal properties, drug permeability, and porosity of free shellac films were investigated. Shellac films were cast from aqueous solutions, and their mechanical properties were studied by tensile test. Thermal analyses were performed using differential scanning calorimetry (DSC). The results showed that the addition of plasticizer caused a decrease in both elastic modulus and glass transition temperature (T(g)) and an increase in elongation at break of free shellac films. This effect was related to the concentrations of plasticizers. Different molecular weights of PEGs have different plasticization mechanisms.Moreover, the incorporation of different amounts of HPMC, MC, or carbomer in free shellac films caused an increase in the flexibility, decrease in T(g), and a marked increase in drug permeability of free shellac films, whereas the addition of PVA caused a decrease in flexibility and drug permeability and an increase in T(g). Addition of EC resulted in a slight decrease of the elasticity and a small decrease in drug permeability. However it does not show a considerable effect on the T(g). In addition, it was found that the drug permeability is directly related to the mechanical properties and T(g) of shellac films.
Article
The use of polymer blends as coating materials for controlled drug delivery systems can offer major advantages, including: (i) facilitated adjustment of desired drug release patterns, mechanical properties and drug release mechanisms, (ii) improved film formation and storage stability, and (iii) the possibility to develop novel strategies for site specific drug delivery within the gastro intestinal tract (e.g., colon targeting). However, these systems are more complex than coatings based on only one polymer and care has to be taken when using this type of formulations. For instance, the blended polymers can be incompatible, aqueous polymer dispersions might flocculate and plasticizers potentially redistribute from one polymer into the other during curing and/or long term storage. This article gives an overview on the current state of the art of the use of polymer blends as coating materials for controlled drug delivery, explaining the major advantages and potential pitfalls. Special emphasis is laid on the underlying drug release mechanisms and practical examples for various types of applications are given. Due to the higher complexity of the systems, a thorough understanding of the most important mass transport phenomena involved in the control of drug release can be very helpful to render the optimization of this type of advanced delivery systems more efficient.
Article
Polymeric film coatings have been applied to solid substrates for decorative, protective, and functional purposes. Irrespective of the reasons for coating, certain properties of the polymer films may be determined as a method to evaluate coating formulations, substrate variables, and processing conditions. This article describes experimental techniques to assess various properties of both free and applied films, including water vapor and oxygen permeability, as well as thermal, mechanical, and adhesive characteristics. Methods to investigate interfacial interactions are also presented.
Article
The aim of this study was to evaluate the moisture-protective ability of different polymeric coatings. Free films and film-coated tablets (with cores containing freeze-dried garlic powder) were prepared using aqueous solutions/dispersions of hydroxypropyl methylcellulose (HPMC), Opadry AMB [a poly(vinylalcohol)-based formulation] and Eudragit E PO [a poly(methacrylate-methylmethacrylate)]. The water content of the systems upon open storage at 75% relative humidity (RH) and 22 degrees C (room temperature) was followed gravimetrically. Furthermore, polymer powders, free films and coated tablets were analyzed by differential scanning calorimetry (DSC) and dynamic vapor sorption (DVS). The type of polymer strongly affected the resulting water uptake kinetics of the free films and coated tablets. DSC analysis revealed whether or not significant physical changes occurred in the coatings during storage, and whether the water vapor permeability was water concentration dependent. Using DVS analysis the critical glass transition RH of Opadry AMB powder and Opadry AMB-coated tablets at 25 degrees C could be determined: 44.0% and 72.9% RH. Storage below these threshold values significantly reduces water penetration. Thus, DVS and DSC measurements can provide valuable information on the nature of polymers used for moisture protection.
The role of high-solids coating systems in reducing process costs
  • S Porter
Porter S. (2010). The role of high-solids coating systems in reducing process costs. Tablets Capsules, 8:10–16.
Investigation of a novel hypromellose polymer for high-productivity tablet coating applications
  • T Rogers
  • P Sheskey
  • H Furukawa
  • C Mallon
  • M Trampe
  • D Holbrook
Rogers T, Sheskey P, Furukawa H, Mallon C, Trampe M, Holbrook D. (2008). Investigation of a novel hypromellose polymer for high-productivity tablet coating applications. AAPS Annual Meeting, Atlanta, GA.
Reducing coated tablet defects from laboratory through production scale: performance of hypromellose or polyvinyl alcohol-based aqueous film coating systems
  • C Cunningham
Cunningham C. (2007). Reducing coated tablet defects from laboratory through production scale: performance of hypromellose or polyvinyl alcohol-based aqueous film coating systems. AAPS Annual Meeting, San Diego, CA.
The mechanical properties of hydroxypropylmethylcellulose films derived from aqueous systems part I: the influence of plasticizers
  • M Aulton
  • M Abdul-Razzak