Physicochemical and release properties of pellets coated with Kollicoat® SR 30 D, a new aqueous polyvinyl acetate dispersion for extended release

Taste-Masked Pellets of Warfarin Sodium: Formulation towards the Dose Personalisation

The bitter drug, warfarin, has a narrow therapeutic index (NTI) and is used in paediatrics and geriatrics. The aim of this feasibility study was to formulate the taste-masked warfarin-containing pellets to be applicable for dose personalisation and to improve patient compliance, as well as to investigate the effect of the core type (PharSQ® Spheres M, CELPHERE™ CP-507, and NaCl) on the warfarin release from the Kollicoat® Smartseal taste-masking-coated pellets. The cores were successfully drug-loaded and coated in a fluid-bed coater with a Wurster insert. An increase in particle size and particle size distribution was observed by optical microscopy. In saliva-simulated pH, at the Kollicoat® Smartseal level of 2 mg/cm2, none of the pellets demonstrated drug release, confirming their efficient taste-masking. However, in a stomach-simulated pH, a faster drug release was observed from PharSQ® Spheres M- and CELPHERE™ CP-507-coated pellets in comparison with NaCl cores. Additional experiments allowed us to explain the slower drug release from NaCl-containing pellets because of the salting-out effect. Despite the successful taste masking, the drug release from pellets was relatively slow (not more than 91% per 60 min), allowing for further formulation improvements.

Impact of Lubrication on Key Properties of Orodispersible Minitablets in Comparison to Conventionally Sized Orodispersible Tablets

Orodispersible minitablets (ODMTs) offer several benefits like easy swallowability, dose flexibility and simple manufacturing through direct compression. In this study, the effect of lubrication on five different co-processed excipients (Ludiflash®, Parteck® ODT, Prosolv® ODT G2, galenIQ™ 721 and SuperTab® 50 ODT) has been studied for orodispersible tablets (ODTs) with 11.28 and 2 mm in diameter. External lubrication was compared with internal lubrication using 0.5 %, 1 % or 2 % magnesium stearate or 1 %, 2 % or 4 % sodium stearyl fumarate. Mechanical strength and disintegration time of the ODTs were evaluated beside the lubrication efficiency. Especially mannitol-based co-processed excipients show strong dependency of the lubricant concentration whereas both ODTs and ODMTs and minitablets with isomalt showed comparable properties for both lubricants and their concentrations. Sodium stearyl fumarate is considered as the preferred lubricant for ODMTs as it showed a higher lubrication efficiency and less negative impact on disintegration time. External lubrication exhibited higher tensile strength for plastic materials, but increased the disintegration time, particularly for ODMTs due to the high specific surface where the lubricant is applied. In general, this study has demonstrated that minitablets require higher lubricant concentrations than conventionally sized tablets.

Tailoring Release Profiles of BCS Class II Drugs Using Controlled Release Amorphous Solid Dispersion Beads with Membrane-Reservoir Design: Effect of Pore Former and Coating Levels

Poor aqueous solubility is a major limiting factor during the development of BCS Class II drug candidates in a solid oral dosage form. Conventional amorphous solid dispersion (ASD) systems focus on maximizing the rate and extent of release by employing water-soluble polymeric crystallization inhibitors; however, they often encounter rapid supersaturation and solution-mediated phase transformation (SMPT). Therefore, in this work, a controlled release membrane was introduced onto ASD beads to mitigate the SMPT problem. A membrane-reservoir controlled release amorphous solid dispersion (CRASD) bead system was designed, and the effects of the coating thickness and pore former content on drug release profiles were investigated. CRASD beads were manufactured by spray-coating polyvinyl acetate with polyvinylpyrollidone (PVP) as a pore former onto sugar bead substrates layered with the ASD reservoir of celecoxib and PVP. Raising the pore former content and/or lowering the coating level imparted higher release rates and supersaturation levels. The extent of release, measured by the area under the curve, was greatest when an optimal balance between the release rate and peak concentration could be established, corresponding to a high pore former/high coating level combination. Attributed to a thicker membrane structure with a higher pore former, rapid initial release could be achieved, yet controlled gradually for several hours, avoiding the critical threshold where the onset of SMPT predominates. The greater membrane capacity to transiently immobilize drug molecules (i.e., preserve amorphicity) and gradually release drug over a prolonged duration may be key to balancing supersaturation on both sides of the membrane; hence coating variables should be tactfully selected to exploit this benefit.

Towards a Better Understanding of Verapamil Release from Kollicoat SR:IR Coated Pellets Using Non-Invasive Analytical Tools

The aim of this study was to gain deeper insight into the mass transport mechanisms controlling drug release from polymer-coated pellets using non-invasive analytical tools. Pellet starter cores loaded with verapamil HCl (10% loading, 45% lactose, 45% microcrystalline cellulose) were prepared by extrusion/spheronization and coated with 5% Kollicoat SR:IR 95:5 or 10% Kollicoat SR:IR 90:10. Drug release was measured from ensembles of pellets as well as from single pellets upon exposure to acetate buffer pH = 3.5 and phosphate buffer pH = 7.4. The swelling of single pellets was observed by optical microscopy, while dynamic changes in the pH in the pellet cores were monitored by fluorescence spectroscopy. Also, mathematical modeling using a mechanistically realistic theory as well as SEM and Raman imaging were applied to elucidate whether drug release mainly occurs by diffusion through the intact film coatings or whether crack formation in the film coatings plays a role. Interestingly, fluorescence spectroscopy revealed that the pH within the pellet cores substantially differed upon exposure to acetate buffer pH = 3.5 and phosphate buffer pH = 7.4, resulting in significant differences in drug solubility (verapamil being a weak base) and faster drug release at lower pH: from ensembles of pellets and single pellets. The monitoring of drug release from and the swelling of single pellets indicated that crack formation in the film coatings likely plays a major role, irrespective of the Kollicoat SR:IR ratio/coating level. This was confirmed by mathematical modeling, SEM and Raman imaging. Importantly, the latter technique allowed also for non-invasive measurements, reducing the risk of artifact creation associated with sample cutting with a scalpel.

Slow release fertilizer prepared with lignin and poly(vinyl acetate) bioblend

Controlled or slow release fertilizers have been recommended to enhance crop yield, while minimizing environmental and economic issues related from current fertilizer applications. However, alternative biodegradable and non-toxic coating material should be suggested to produce biocoated fertilizers. Here we propose the use of lignin and poly(vinyl acetate) (PVAc) as biocoating materials for preparing slow release urea fertilizer. The blend of PVAc and lignin at a mass ratio of 75:25 improved the characteristics of the formed film and increased the nitrogen release time if compared to the pure polymers. The nitrogen release time from urea granules coated with a polymeric layer of 154.3 ± 5.5 μm formed by lignin and PVAc was 36 times greater than from bare urea. The increase in the polymeric coating from 52.6 ± 5.2 to 80.2 ± 6.1 μm decreased the curvature of the nitrogen release data by a factor of at least 1.7, while the curvature was decreased in at least 1.3 with the increase in the polymeric coating from 80.2 ± 6.1 to 158.9 ± 10.6 μm. The adjustment of nitrogen release data to the Peppas-Sahlin model indicated the Fickian diffusion is more predominant than relaxation contributions, since the used polymers did not present considerable swelling. Thus, the blending of PVAc and lignin at 25 wt% of lignin and 75 wt% of PVAc is suggested as a biocoating material for producing slow release fertilizers.

Quantification of porogen effect on the drug release from single- and multi-layered ethylcellulose coated pellets containing single or combined drugs

The aim of this work was to develop a mathematical model to estimate the drug release from a conventional single-compartment reservoir pellet and extend its applicability to multi-compartment reservoir pellets. Conventional pellets were prepared by layering the drug onto starter-core then applying various ethylcellulose/HPC coatings for drug release control. Multi-layered pellets comprised a first drug layer of propranolol HCl (D₁) followed by a first controlled release coating (C₁) and consecutively a second drug layer of carbamazepine or caffeine (D₂) and then a second controlled-release coating (C₂). Drug release from single- and multi-compartment pellets generally increased with an increase of the water-soluble HPC in the coatings. The response described a sigmoidal curve, which agreed with a cumulative normal distribution function. The developed mathematical model facilitated quantification of the drug release of pellets as a function of the porogen content and the coating level. Additionally, the model was applied successfully in multi-compartment pellets to calculate theses effects on the release of drugs with a broad range of aqueous solubility.

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.

Feedforward and Feedback Control of a Pharmaceutical Coating Process

This work demonstrates the use of a combination of feedforward and feedback loops to control the controlled release coating of theophylline granules. Feedforward models are based on the size distribution of incoming granules and are used to set values for the airflow in the fluid bed processor and the target coat weight to be applied to the granules. The target coat weight of the granules is controlled by a feedback loop using NIR spectroscopy to monitor the progress of the process. By combining feedforward and feedback loops, significant variation in the size distributions and ambient conditions were accommodated in the fluid bed coating of the granules and a desired dissolution profile was achieved. The feedforward component of the control system was specifically tested by comparing the performance of the control system with and without this element by Monte Carlo simulation.

Retrospective Quality by Design (rQbD) applied to the optimization of orodispersible films

The study demonstrates the application of QbD based on historical data for a product at a later development stage - retrospective QbD (rQbD). More specifically, it is investigated the root-cause for the observed slower drug release in Orodispersible Films (ODFs) during storage. Risk assessment tools were used to identify parameters affecting ODFs critical quality attributes, namely percent drug release and residual water content. The parameters room temperature, room relative humidity, drying temperature and mixing equipment were used in the statistical modeling of the available data. The estimated models were then used to define the feasible working region. Statistical modeling indicates that initial residual water content of the ODFs is mainly affected by 2nd order interactions of room temperature, room relative humidity and drying temperature, while the stability of drug release profile is mostly influenced by room temperature and an interaction between room relative humidity and drying temperature. Depending on the drying temperature employed the effect of room temperature and room relative humidity change significantly. This work shows that it is possible to apply rQbD to achieve a greater understanding of the manufacturing process of ODFs and to define a proper design space.

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.

Comparative Study Between Different Ready-Made Orally Disintegrating Platforms for the Formulation of Sumatriptan Succinate Sublingual Tablets

Sumatriptan succinate (SS) is a selective serotonin receptor agonist used for the treatment of migraine attacks, suffering from extensive first-pass metabolism and low oral bioavailability (∼14%). The aim of this work is to compare the performance of different ready-made co-processed platforms (Pharmaburst®, Prosolv ODT®, Starlac®, Pearlitol Flash®, or Ludiflash®) in the formulation of SS sublingual orodispersible tablets (ODTs) using direct compression technique. The prepared SS ODT formulae were evaluated regarding hardness, friability, simulated wetting time, and in vitro disintegration and dissolution tests. Different mucoadhesive polymers-HPMC K4M, Carbopol®, chitosan, or Polyox®-were tested aiming to increase the residence time in the sublingual area. A pharmacokinetic study on healthy human volunteers was performed, using LC/MS/MS assay, to compare the optimum sublingual formula (Ph25/HPMC) with the conventional oral tablet Imitrex®. Results showed that tablets prepared using Pharmaburst® had significantly (p < 0.05) the lowest simulated wetting and in vitro disintegration times of 17.17 and 23.50 s, respectively, with Q _5 min of 83.62%. HPMC showed a significant (p < 0.05) increase in the residence time from 48.44 to 183.76 s. The relative bioavailability was found to be equal to 132.34% relative to the oral tablet Imitrex®. In conclusion, Pharmaburst® was chosen as the optimum ready-made co-processed platform that can be successfully used in the preparation of SS sublingual tablets for the rapid relief of migraine attacks.

Importance of air bubbles in the core of coated pellets: Synchrotron X-ray microtomography allows for new insights

High-resolution X-ray microtomography was used to get deeper insight into the underlying mass transport mechanisms controlling drug release from coated pellets. Sugar starter cores were layered with propranolol HCl and subsequently coated with Kollicoat SR, plasticized with 10% TEC. Importantly, synchrotron X-ray computed microtomography (SR-μCT) allowed direct, non-invasive monitoring of crack formation in the film coatings upon exposure to the release medium. Propranolol HCl, as well as very small sugar particles from the pellets' core, were expulsed through these cracks into the surrounding bulk fluid. Interestingly, SR-μCT also revealed the existence of numerous tiny, air-filled pores (varying in size and shape) in the pellet cores before exposure to the release medium. Upon water penetration into the system, the contents of the pellet cores became semi-solid/liquid. Consequently, the air-pockets became mobile and fused together. They steadily increased in size (and decreased in number). Importantly, "big" air bubbles were often located in close vicinity of a crack within the film coating. Thus, they play a potentially crucial role for the control of drug release from coated pellets.

Effect of Antiadherents on the Physical and Drug Release Properties of Acrylic Polymeric Films

Antiadherents are used to decrease tackiness of a polymer coating during both processing and subsequent storage. Despite being a common excipient in coating formulae, antiadherents may affect mechanical properties of the coating film as well as drug release from film-coated tablets, but how could addition of antiadherents affect these properties and to what extent and is there a relation between the physical characteristics of the tablet coat and the drug release mechanisms? The aim of this study was to evaluate physical characteristics of films containing different amounts of the antiadherents talc, glyceryl monostearate, and PlasACRYL(TM) T20. Eudragit RL30D and Eudragit RS30D as sustained release polymers and Eudragit FS30D as a delayed release material were used. Polymer films were characterized by tensile testing, differential scanning calorimetry (DSC), microscopic examination, and water content as calculated from loss on drying. The effect of antiadherents on in vitro drug release for the model acetylsalicylic acid tablets coated with Eudragit FS30D was also determined. Increasing talc concentration was found to decrease the ability of the polymer films to resist mechanical stress. In contrast, glyceryl monostearate (GMS) and PlasACRYL produced more elastic films. Talc at concentrations higher than 25% caused negative effects, which make 25% concentration recommended to be used with acrylic polymers. All antiadherents delayed the drug release at all coating levels; hence, different tailoring of drug release may be achieved by adjusting antiadherent concentration with coating level.

Pediatric drug formulation of sodium benzoate extended-release granules

Urea cycle disorders are a group of inherited orphan diseases leading to hyperammonemia. Current therapeutic strategy includes high doses of sodium benzoate leading to three or four oral intakes per day. As this drug is currently available in capsules or in solution, children are either unable to swallow the capsule or reluctant to take the drug due to its strong bitter taste. The objective of the present study was to develop solid, multiparticulate formulations of sodium benzoate, which are suitable for pediatric patients (i.e. flavor-masked, easy to swallow and with a dosing system). Drug layering and coating in a fluidized bed were applied for preparing sustained-release granules. Two types of inert cores (GalenIQ® and Suglets®) and three different polymers (Kollicoat®, Aquacoat® and Eudragit®) were tested in order to select the most appropriate polymer and starter core for our purpose. Physical characteristics and drug release profiles of the pellets were evaluated. A Suglets® core associated with a Kollicoat® coating seems to be the best combination for an extended release of sodium benzoate. A curing period of 8 h was necessary to complete film formation and the resulting drug release pattern was found to be dependent of the acidity of the release medium.

Application of active layering and coating techniques in the development of a multiparticulate, controlled release dosage form of a high-dose, highly soluble drug

CONTEXT

The success of the development of controlled release, multilayered, multiparticulate dosage form of a high-dose, highly-soluble drug is dependent upon proper material and processing choices.

OBJECTIVE

To develop a controlled release dosage form of diltiazem hydrochloride using active layering and coating.

METHODS

Active layering was achieved by spraying a drug solution onto sugar cores using polyvinyl alcohol - polyethylene glycol as a binder. Layered pellets with highest loading and lowest binder content were coated using aqueous dispersions of polyvinyl acetate (PVAc). The effects of the plasticizer and curing on drug release were evaluated.

RESULTS AND DISCUSSION

The binder level had no effect on the process efficiency. Drug release from PVAc-coated pellets was slowed by increasing PVAc level. Plasticization slowed drug release in comparison to nonplasticized formulations. Curing affected drug release of nonplasticized formulations only. Protection against humidity was essential in stabilizing drug release under stability study conditions.

CONCLUSION

Materials and process used were suitable to face the challenge posed by the high dose of the water-soluble drug on the success of the formulation. The effects of the plasticizer, curing and ability of packaging to protect against elevated humidity on the performance of the studied system should be considered in development.

Study of drug release and tablet characteristics of silicone adhesive matrix tablets

Matrix tablets of a model drug acetaminophen (APAP) were prepared using a highly compressible low glass transition temperature (T(g)) polymer silicone pressure sensitive adhesive (PSA) at various binary mixtures of silicone PSA/APAP ratios. Matrix tablets of a rigid high T(g) matrix forming polymer ethyl cellulose (EC) were the reference for comparison. Drug release study was carried out using USP Apparatus 1 (basket), and the relationship between the release kinetic parameters of APAP and polymer/APAP ratio was determined to estimate the excipient percolation threshold. The critical points attributed to both silicone PSA and EC tablet percolation thresholds were found to be between 2.5% and 5% w/w. For silicone PSA tablets, satisfactory mechanical properties were obtained above the polymer percolation threshold; no cracking or chipping of the tablet was observed above this threshold. Rigid EC APAP tablets showed low tensile strength and high friability. These results suggest that silicone PSA could eliminate issues related to drug compressibility in the formulation of directly compressed oral controlled release tablets of poorly compressible drug powder such as APAP. No routinely used excipients such as binders, granulating agents, glidants, or lubricants were required for making an acceptable tablet matrix of APAP using silicone PSA.

Fluid-bed coater modifications and study of their influence on the coating process of pellets

OBJECTIVE

In this study, different modifications of bottom spray fluid-bed coater with draft tube inserted were characterized and evaluated.

MATERIALS AND METHODS

After coating the neutral pellets with polymeric solution comprising coloring agent pellet batches were characterized for coating variation, yield and degree of agglomeration.

RESULTS

Funnel-shaped distribution plate was found to improve process yield and decrease the degree of agglomeration at selected values of process parameters, whereas coating uniformity was worse in all cases when compared to conventional Wurster chamber. Results of the coating chamber with the swirl airflow generator indicate more uniform deposition of the coating material and in some cases an improved process yield and decreased formation of agglomerates when compared to conventional Wurster chamber. In series of experiments using Wurster chamber, having tangentially oriented air intake slots, which enabled introduction of air above the distribution plate, coating layer was more uniformly deposited on the pellet cores and formation of agglomerates was lower compared to the results obtained in a conventional Wurster coating chamber.

CONCLUSION

Modifications of Wurster coating process by introducing swirling air motion within the draft tube or by introduction of air above the distribution plate have at selected values of process parameters resulted in reduced per-particle coating variation, degree of agglomeration and improved process yield.

Preparation of Coated Valproic Acid and Sodium Valproate Sustained-release Matrix Tablets

The aim of this research was to investigate the technique for preparation of coated valproic acid and sodium valproate sustained-release matrix tablets. Different diluents were tested and selected as the effective absorbent for oily valproic acid. Effect of the amount of absorbent and hydroxypropylmethylcellulose on drug release from valproic acid-sodium valproate matrix tablets prepared with wet granulation technique was evaluated in pH change system. Colloidal silicon dioxide effectively adsorbed liquid valproic acid during wet granulation and granule preparation. The amounts of colloidal silicon dioxide and hydroxypropylmethylcellulose employed in tablet formulations affected drug release from the tablets. The drug release was prominently sustained for over 12 h using hydroxypropylmethylcellulose-based hydrophilic matrix system. The mechanism of drug release through the matrix polymer was a diffusion control. The drug release profile of the developed matrix tablet was similar to Depakine Chrono^®, providing the values of similarity factor (f2) and difference factor (f1) of 85.56 and 2.37, respectively. Eudragit^® L 30 D-55 was used as effective subcoating material for core matrix tablets before over coating with hydroxypropylmethylcellulose film with organic base solvent. Drug release profile of coated matrix tablet was almost similar to that of Depakine Chrono^®.

Key formulation variables in tableting of coated pellets

Multiple unit controlled release dosage forms offer various advantages over their single unit counterparts. Most of these advantages are associated with the uniform distribution of multiparticulates throughout the gastrointestinal tract. Though coated pellets can be filled into hard gelatin capsules, tablet formulation is the preferred one because of various advantages associated with it. However, compression of coated pellets is a challenging task necessitating the optimization of various formulation and process variables. The key formulation variables include composition, porosity, size, shape and density of the pellets; type and amount of polymer coating; nature, size and amount of tableting excipients. The pellet core should be strong with some degree of plasticity. It should be highly porous, small, with an irregular shape. The critical density to achieve prolonged release was reported to lie between 2.4 and 2.8 g/cm³. Acrylic polymer films are more flexible and more suitable for the coating of pellets to be compressed into tablets. Thicker coatings offer better resistance to frictional forces. Solvent based coatings are more flexible and have a higher degree of mechanical stability than the aqueous based ones. The tableting excipients should have cushioning property. They should not be significantly different in size and density from those of the pellet cores in order to avoid segregation. Addition of 30%-60% of tableting excipients is necessary to avoid any damage to the polymer coat and to retain its functional property.

Comparative study of the uniformity of coating thickness of pellets coated with a conventional Wurster chamber and a swirl generator-equipped Wurster chamber

This study evaluated the performance of two bottom-spray coaters and the effect of pellet-size variability on coating uniformity. A conventional Wurster chamber was used for the first group of trials, and a Wurster chamber with a novel swirl-flow generator design was used for the second. The results confirmed that when using a conventional Wurster coating chamber, pellets with a smaller diameter receive significantly less coating material compared to those with larger diameters. The swirl generator-equipped Wurster chamber achieved close to uniform coating thickness regardless of pellet size. The ratio (M(S)) of the mass of dye deposited in the coating layer to pellet surface area indicates that coating was much more evenly distributed using the swirl-flow coater. Coating thickness was also analyzed using SEM micrographs and the results were in close agreement with the M(S) factor values. Inter-particle coating mass variation was also lower in case of swirl-flow coater. The results of this study show that a swirl-flow coater is suitable for coating particles of variable size. They also showed an improvement in coating process yield when using the swirl-flow coater.

Simple preparation of coated resin complexes and their incorporation into fast-disintegrating tablets

Even though ion-exchange resins are good drug carriers to get sustained release properties, it may not be good enough only with themselves. For further sustained release effect, a diffusion barrier or coating on the resins' surface can be utilized. Initially, microencapsulation using a w/o/w double emulsion method was used to apply ethylcellulose (EC) onto the drug/resin complexes. Typical pharmaceutical waxes can be alternative materials to delay the drug release from the complex. After the coating, the coated resin particles were incorporated into fast-disintegrating tablets to get an idea regarding the effects of wet granulation and compression on the release. Among the different grades of ECs tested (Ethocel 20, 45, and 100), more viscous EC resulted in better morphologies and sustained release effects. Because the drug release rate was significantly dependent on the coating level, the release rate can be modified easily by changing different levels of the coating. The drug release rate was also strongly dependent on the granulation and compaction process as the coated particles were incorporated into the tablet dosage form. Among the tested waxes, stearic acid had an effect on the sustained release together with lubrication and wetting properties. Even though microencapsulation or wax coating may not be practical for real manufacturing, the results may give valuable information how to formulate sustained release dosage forms and their properties on the tablet preparation.

Pectin/Kollicoat SR30D isolated films for colonic delivery [I]: a comparison of normal and colitis-induced models to assess the efficiency of microbially triggered drug delivery

Objectives

The purpose of the study was to evaluate digestion of pectin/Kollicoat SR30D free films for colonic delivery in vitro and in vivo.

Methods

Free films containing different ratios of pectin to Kollicoat SR30D were prepared by casting/solvent evaporation method. An in-vitro comparison of swelling, degradation and permeability of the free films was carried out in simulated colon fluids containing caecal contents from normal rats with colitis induced by 2,4,6-trinitrobenzene sulfonic acid (TNBS) or oxazolone. A comparative in-vivo evaluation of degradation was also conducted in normal and colitis-induced model rats.

Key findings

The pectin within the mixed films was susceptible to rat colonic bacterial enzymes. The extent of digestion correlated with the amount of pectin present within the film. In vitro, the swelling index, drug permeability and extent of film digestion in simulated colon fluids with caecal contents obtained from normal rats were higher than from TNBS- or oxazolone-induced model rats, whereas in-vivo degradation was similar in the three groups of rats. The pectin/Kollicoat SR30D free films were completely degraded in the colitis-induced rats.

Conclusions

Pectic/Kollicoat SR30D films may be useful as coatings to target delivery of drugs to the colon.

Safety and robustness of coated pellets: self-healing film properties and storage stability

PURPOSE

Aim of the study was to verify the safety of chlorpheniramine maleate pellets, coated with blends of poly(vinyl acetate) and poly(vinyl alcohol)-poly(ethylene glycol) graft copolymer. Therefore, the impact of mechanical forces and storage conditions on the drug release was investigated.

RESULTS

Similar release profiles before and after compression of the pellets to tablets underlined the high film robustness. A damage of the film coat with a razor blade resulted in a premature release, but without a burst. After a similar damage with a needle, the release profile remained almost unchanged, which indicated a swelling based self repair mechanism of the film. Additional studies were dedicated to the storage stability at three different conditions. A slightly delayed release was obtained after 6 months storage at 25 degrees C and a marginally accelerated release was measured after storage at elevated temperatures. No drug migration into the coating layer was detected during storage by confocal Raman microscopy. (1)H-NMR analysis during storage demonstrated, that no polymer or drug degradation had occurred and the plasticizer concentration remained constant.

CONCLUSION

The polyvinyl based coating blend for modified release pellets demonstrated a high safety, due to their high robustness and compressibility as well as their satisfying storage stability.

Drug release mechanisms from ethylcellulose: PVA-PEG graft copolymer-coated pellets

The aim of this study was to better understand the underlying drug release mechanisms from aqueous ethylcellulose-coated pellets containing different types of drugs and starter cores. Theophylline, paracetamol, metoprolol succinate, diltiazem HCl and metoprolol tartrate were used as model drugs exhibiting significantly different solubilities (e.g. 14, 19, 284, 662 and 800 mg/mL at 37 degrees C in 0.1N HCl). The pellet core consisted of a drug matrix, drug-layered sugar bead or drug-layered microcrystalline cellulose (MCC) bead, generating different osmotic driving forces upon contact with aqueous media. Importantly, the addition of small amounts of poly(vinyl alcohol)-poly(ethylene glycol) graft copolymer (PVA-PEG graft copolymer) to the ethylcellulose coatings allowed for controlled drug release within 8-12h, irrespective of the type of drug and composition of the pellet core. Drug release was found to be controlled by diffusion through the intact polymeric membranes, irrespective of the drug solubility and type of core formulation. The ethylcellulose coating was dominant for the control of drug release, minimizing potential effects of the type of pellet core and nature of the surrounding bulk fluid, e.g. osmolality. Thus, this type of controlled drug delivery system can be used for very different drugs and is robust.

New insight into modified release pellets - Internal structure and drug release mechanism

The aim of the study was to explore the drug release mechanism from pellets, coated with blends of poly(vinyl acetate) (PVAc) and polyvinyl alcohol-polyethylene glycol graft copolymer (PVA-PEG). Water influx and drug solubilization inside the pellets were investigated in correlation to drug release. The highly soluble drug Chlorpheniramine maleate (CPM) was used as a model compound. Modified release pellets were manufactured by fluid bed drug layering and film coating of starter beads. The pellets were characterized using cross section EDX mapping, confirming location and homogeneity of the different layers. A film coat of 23%, containing PVAc/PVA-PEG in 9:1 ratio, resulted in a sigmoid shaped release curve with 2 h lag-time, followed by 3 h of continuous drug release. Using NMR analysis, water influx and drug solubilization inside the pellets were detected within 20 min. Additionally, dissolution of PVA-PEG after several minutes and drug release after the lag-time were measurable. A fast water influx into PVAc/PVA-PEG film coated pellets did not result in a fast drug release. Despite a fast drug solubilization within the pellets, drug release was initiated after 2 h, suggesting a one way stream of water during the observed lag-time.

A Novel Salted-out and Subsequently Crosslinked Poly(Lactic-co-Glycolic Acid) Polymeric Scaffold Applied to Monolithic Drug Delivery

This study involved a statistical approach to develop a mechanistic understanding of the salting-out of poly(lactic-co-glycolic acid) (PLGA) and to evaluate the capacity to modulate the physicochemical and physicomechanical properties of PLGA by incorporating electrolytes that produce stochastic fluctuations. The correlation between the three types of salts used and the extent of PLGA chain transitions were established by structural-thermal analysis. Drug-loaded monolithic matrices are prepared by direct compressing salted-out PLGA and a model drug (melatonin). PLGA scaffolds possess fiber diameters and volumes ranging between 0.1—15 μm and 0.0075—14,000 μm3 , respectively. Texture profile analysis reveal a significant increase in the energy absorbed and matrix resilience with increased NaCl2 and AlCl3 concentrations. In vitro drug release studies were performed in phosphate buffered saline (pH 7.4; 37°C); the release media was sampled at pre-determined intervals and analyzed by UV spectroscopy. Ideal zero-order drug release profiles were observed with 20% melatonin over a 30-day period. Monolithic matrices prepared by crosslinking melatonin with PLGA reveal a superior capability to control drug release. The salting-out and subsequent crosslinking of PLGA significantly modified the physicochemical and physicomechanical properties of native PLGA and demonstrated the ability to achieve controlled drug release.

Characterization of coating systems

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.