Influence of an enteric polymer on drug release rates of theophylline from pellets coated with Eudragit RS 30D

Direct cyclodextrin based powder extrusion 3D printing of budesonide loaded mini-tablets for the treatment of eosinophilic colitis in paediatric patients

The purpose of this study was to combine direct powder extrusion (DPE) 3D printing and fluid bed coating techniques to create a budesonide (BD) loaded solid oral formulations for the treatment of eosinophilic colitis (EC) in paediatric patients. The preferred medication for EC treatment is BD, which has drawbacks due to its poor water solubility and low absorption. Additionally, since commercially available medications for EC treatment are created and approved for adult patients, administering them to children sometimes requires an off-label use and an impromptu handling, which can result in therapeutic ineffectiveness. The DPE 3D approach was investigated to create Mini-Tablets (MTs) to suit the swallowing, palatability, and dose flexibility control requirements needed by paediatric patients. Additionally, DPE 3D and the inclusion of hydroxypropyl-β-cyclodextrin in the initial powder mixture allowed for an improvement in the solubility and rate of BD dissolution in aqueous medium. Then, to accomplish a site-specific drug release at the intestinal level, MTs were coated with a layer of Eudragit FS 30D, an enteric polymer responsive at pH > 7.0 values. In vitro release experiments showed that film-coated MTs were suitable in terms of size and dose, enabling potential therapeutic customization and targeted delivery of BD to the colon.

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.

Coatings of Eudragit® RL and L-55 Blends: Investigations on the Drug Release Mechanism

In a previous study, generally lower drug release rates from RL:L55 blend coated pellets in neutral/basic release media than in acidic release media were reported. The aim of this study was to obtain information on the drug release mechanism of solid dosage forms coated with blends of Eudragit® RL (RL) and Eudragit® L-55 (L55). Swelling experiments with free films were analyzed spectroscopically and gravimetrically to identify the physicochemical cause for this release behavior. With Raman spectroscopy, the swelling of copolymer films could be monitored. IR spectroscopic investigations on RL:L55 blends immersed in media at pH 6.8 confirmed the formation of interpolyelectrolyte complexes (IPECs) that were not detectable after swelling in hydrochloric acid pH 1.2. Further investigations revealed that these IPECs decreased the extent of ion exchange between the quaternary ammonium groups of RL and the swelling media. This is presumably the reason for the previously reported decreased drug permeability of RL:L55 coatings in neutral/basic media as ion exchange is the determining factor in drug release from RL coated dosage forms. Gravimetric erosion studies confirmed that L55 was not leached out of the film blends during swelling in phosphate buffer pH 6.8. In contrast to all other investigated films, the 4:1 (RL:L55) blend showed an extensive swelling within 24 h at pH 6.8 which explains the reported sigmoidal release behavior of 4:1 blend coated pellets. These results help to understand the release behavior of RL:L55 blend coated solid dosage forms.

Impact of anti-tacking agents on properties of gas-entrapped membrane and effervescent floating tablets

Tackiness caused by the gas-entrapped membrane (Eudragit(®)RL 30D) was usually observed during storage of the effervescent floating tablets, leading to failure in floatation and sustained release. In this work, common anti-tacking agents (glyceryl monostearate (GMS) and talc) were used to solve this tackiness problem. The impact of anti-tacking agent on the properties of free films and corresponding floating tablets was investigated. GMS was more effective than talc in reducing tackiness of the film. Addition and increasing amount of anti-tacking agents lowered the film mechanical strength, but the coating films were still strong and flexible enough to resist the generated gas pressure inside the floating tablet. Wettability and water vapor permeability of the film decreased with increasing level of anti-tacking agents as a result of their hydrophobicity. No interaction between anti-tacking agents and polymer was observed as confirmed by Fourier transform infrared spectroscopy, powder X-ray diffractometry, and differential scanning calorimetry studies. Increasing amount of anti-tacking agents decreased time to float and tended to retard drug release of the floating tablets. Floating properties and drug release were also influenced by type of anti-tacking agents. The obtained floating tablets still possessed good floating properties and controlled drug release even though anti-tacking agent had some effects. The results demonstrated that the tackiness problem of the floating tablets could be solved by incorporating anti-tacking agent into the gas-entrapped membrane.

Development of enteric submicron particle formulation of papain for oral delivery

BACKGROUND

Particulate systems have received increasing attention for oral delivery of biomolecules. The objective of the present study was to prepare submicron particulate formulations of papain for pH-dependent site-specific release using pH-sensitive polymers.

METHODS

Enteric submicron particle formulations of papain were prepared by w/o/w emulsion solvent evaporation using hydroxypropyl methylcellulose phthalate (HPMCP), Eudragit L100, and Eudragit S100, to avoid gastric inactivation of papain.

RESULTS

Smaller internal and external aqueous phase volumes provided maximum encapsulation efficiency (75.58%-82.35%), the smallest particle size (665.6-692.4 nm), and 25%-30% loss of enzyme activity. Release studies in 0.1 N HCl confirmed the gastroresistance of the formulations. The anionic submicron particles aggregated in 0.1 N HCl (ie, gastric pH 1.2) due to protonation of carboxylic groups in the enteric polymer. Aggregates < 500 μm size would not impede gastric emptying. However, at pH > 5.0 (duodenal pH), the submicron particles showed deaggregation due to restoration of surface charge. HPMCP submicron particles facilitated almost complete release of papain within 30 minutes at pH 6.0, while Eudragit L100 and Eudragit S100 particles released 88.82% and 53.00% of papain at pH 6.8 and pH 7.4, respectively, according to the Korsmeyer-Peppas equation. Sodium dodecyl sulfate polyacrylamide gel electrophoresis and fluorescence spectroscopy confirmed that the structural integrity of the enzyme was maintained during encapsulation. Fourier transform infrared spectroscopy revealed entrapment of the enzyme, with powder x-ray diffraction and differential scanning calorimetry indicating an amorphous character, and scanning electron microscopy showing that the submicron particles had a spherical shape.

CONCLUSION

In simulated gastrointestinal pH conditions, the HPMCP, Eudragit L100, and Eudragit S100 submicron particles showed good digestion of paneer and milk protein, and could serve as potential carriers for oral enzyme delivery. Stability studies indicated that formulations with approximately 6% overage would ensure a two-year shelf-life at room temperature.

Pharmaceutical acrylic beads obtained by suspension polymerization containing cellulose nanowhiskers as excipient for drug delivery

Direct compression is one of the most popular techniques to prepare tablets but only a few commercial excipients are well adapted for this process into controlled release formulations. In the last years, the introduction of new materials for drug delivery matrix tablets has become more important. This paper evaluated the physicochemical and flow properties of new polymeric excipient of ethyl acrylate, methyl methacrylate and butyl metacrylate, synthesized by suspension polymerization using cellulose nanowhiskers as co-stabilizer, to be used as direct compression for modified release tablets. Infrared spectroscopy (FTIR) confirmed the success of the copolymerization reaction. Scanning electron microscopy (SEM) showed that excipient was obtained how spherical beads. Thermal properties of the beads were characterized by thermogravimetric (TG) analysis. Particle size analysis of the beads with cellulose nanowhiskers (CNWB) indicated that the presence of the nanowhiskers led to a reduction of particle size and to a narrower size distribution. In vitro test showed that the nanowhiskers and beads produced are nontoxic. Parameters such as Hausner ratio, Carr's index and cotangent of angle α were employed to characterize the flow properties of CNWB beads. Furthermore, the beads are used to produce tablets by direct compression contained propranolol hydrochloride as model drug. Dissolution tests performed suggested that beads could be used as excipient in matrix tablets with a potential use in drug controlled release.

Influence of an acrylic polymer blend on the physical stability of film-coated theophylline pellets

The purpose of this study was to investigate the physical stability of a coating system consisting of a blend of two sustained release acrylic polymers and its influence on the drug release rate of theophylline from coated pellets. The properties of both free films and theophylline pellets coated with the polymer blend were investigated, and the miscibility was determined via differential scanning calorimetry. Eudragit RS 30 D was plasticized by the addition of Eudragit NE 30 D, and the predicted glass transition temperature (T(g)) of the blend was similar to the experimental values. Sprayed films composed of a blend of Eudragit NE 30 D/Eudragit RS 30 D (1:1) showed a water vapor permeability six times greater than films containing only Eudragit NE 30 D. The presence of quaternary ammonium functional groups from the RS 30 D polymer increased the swellability of the films. The films prepared from the blend exhibited stable permeability values when stored for 1 month at both 25 degrees C and 40 degrees C, while the films which were composed of only Eudragit NE 30 D showed a statistically significant decrease in this parameter when stored under the same conditions. Eudragit NE 30 D/Eudragit RS 30 D (1:1)-sprayed films decreased in elongation from 180% to 40% after storage at 40 degrees C for 1 month, while those stored at 25 degrees C showed no change in elongation. In coated pellets, the addition of Eudragit RS 30 D to the Eudragit NE 30 D increased the theophylline release rate, and the pellets were stable when stored at 25 degrees C for a period of up to 3 months due to maintenance of the physico-mechanical properties of the film. Pellets stored at 40 degrees C exhibited a decrease in drug release rate over time as a result of changes in film physico-mechanical properties which were attributed to further coalescence and densification of the polymer. When the storage temperature was above the T(g) of the composite, instabilities in both drug release rate and physical properties were evident. Stabilization in drug release rate from coated pellets could be correlated with the physico-mechanical stability of the film formulation when stored at temperatures below the T(g) of the polymer.

Controlled release solid dosage forms using combinations of (meth)acrylate copolymers

Controlled release solid oral dosage forms have been widely used for decades, enabling drugs to be administered more comfortably while at the same time providing a sustained and reproducible method of release. (Meth)acrylate copolymers are one of the options available when considering a sustained release solid form. Due to their different functionalities it is possible to achieve various different release profiles. The electrical character of these copolymers and their pH-dependent solubility can result in new and modified patterns when these polymers are combined. This review sheds light on various studies involving combinations of (meth)acrylate copolymers for use in multi-unit systems and matrix tablets, and also on several analytical methods that help to identify possible interactions between these polymers.

Reduction of Gastric Ulcerogenicity During Multiple Administration of Diclofenac Sodium by a Novel Solid-in-Oil Suspension

This article reports a significant reduction of gastric ulcerogenicity by complex formation of a nonsteroidal anti-inflammatory drug with surfactants. Diclofenac sodium (DFNa) was suspended in medium chain triglyceride (MCT) by forming a complex with an edible lipophilic surfactant. Two types of suspensions, prepared through a membrane emulsification with different pore sizes, were evaluated according to the degree of gastric damage following multiple oral administration in rats. It was shown that gastric ulcerogenicity of DFNa was reduced by the surfactant-drug complexes, at doses up to 12 mg/kg, whereas severe gastric damage was observed upon oral administration of the aqueous solution at doses of 6 mg/kg. Comparable blood levels of DFNa were observed after administration of solution and suspension formulations.

Use of Proteins to Minimize the Physical Aging of EUDRAGIT® Sustained Release Films

The objective of this study was to investigate the influence of two proteins, albumin and type B gelatin, on the physical aging of EUDRAGIT RS 30 D and RL 30 D coated theophylline pellets. The physicomechanical properties of sprayed films, thermal properties of cast films, influence of proteins on the zeta potential and particle size of the dispersion, and the release of proteins from cast films under simulated dissolution conditions were investigated. The release rate of theophylline decreased significantly over time from pellets coated with an acrylic dispersion containing 10% albumin when there was no acidification of the acrylic dispersion; however, when pellets were coated with an acidified EUDRAGIT/albumin dispersion, the theophylline release rate was stable for dosage forms stored in the absence of humidity. The drug release rate was faster for pellets coated with acrylic dispersions containing 10% gelatin compared to the albumin-containing formulations. When sprayed films were stored at 40 degrees C/75% RH, the water vapor permeability decreased significantly for both EUDRAGIT films and those containing EUDRAGIT and albumin; however, there was no significant change in this parameter when 10% gelatin was present. Albumin was released from the acrylic films when the pH of the dissolution media was below the isoelectric point of the protein while no quantitative release of gelatin was observed in pH 1.2 or 7.4 media. The effect of gelatin to prevent the decrease in drug release rate was due to stabilization in water vapor permeability of the film. Acidification of the polymeric dispersion resulted in electrostatic repulsive forces between albumin and the acrylic polymer, which stabilized the drug release rate when the dosage forms were stored in aluminum induction sealed containers at both 40 degrees C/75% RH and 25 degrees C/60% RH.

Effect of Eudragit RS 30D and talc powder on verapamil hydrochloride release from beads coated with drug layered matrices

The aim of this study was to investigate the effect of Eudragit RS 30D, talc, and verapamil hydrochloride on dissolution and mechanical properties of beads coated with "drug-layered matrices". This was accomplished with the aid of a three-factor multiple-level factorial design using percent drug release in 1 and 2 h, T(50), tensile strength, brittleness, stiffness and toughness as the responses. Beads were coated in a fluidized-bed coating unit. Surface morphology and mechanical properties were evaluated by surface profilometry and texture analysis, respectively. No cracks, flaws and fissures were observed on the surfaces. The mechanical properties were dependent on the talc/polymer ratio. The release of verapamil from the beads was influenced by matrix components. Increasing the level of both talc and Eudragit decreased the percent drug released from 67% to 4.8% and from 80.7% to 6.7% in 1 and 2 h, respectively, and increased T(50) from 0.8 to 25.7 h. It was concluded that beads could be efficiently coated with "drug-layered matrices". The release of drug, however, depends on a balance between the levels of drug, talc, and polymer, whereby desired dissolution and mechanical properties could be controlled by the talc/polymer ratio and the level of drug loading.

pH-Sensitive Polymer Blends Used as Coating Materials to Control Drug Release from Spherical Beads: Elucidation of the Underlying Mass Transport Mechanisms

PURPOSE

To elucidate the drug release mechanisms from pellets coated with pH-sensitive polymer blends.

METHODS

Verapamil hydrochloride-loaded beads were coated with various blends of a water-insoluble and an enteric polymer, ethylcellulose:Eudragit L and Eudragit NE:Eudragit L, respectively. Both experimental and theoretical techniques were used to characterize the systems before and upon exposure to 0.1 M HCl and phosphate buffer (pH 7.4).

RESULTS

Using analytical solutions of Fick's second law of diffusion, optical and scanning electron microscopy, and mechanical and gravimetric analysis, new insight into the underlying drug release mechanisms could be gained. More importantly, the latter can be effectively altered by varying the type of polymer blend and blend ratio. For example, at low pH drug release is primarily controlled by diffusion through the intact film coatings in Eudragit NE:Eudragit L blends, whereas crack formation is of major importance in ethylcellulose:Eudragit L-coated systems. At high pH, the (partial) leaching of the enteric polymer out of the coatings plays an important role. In all cases, the observed drug release profiles could be explained based on the occurring mass transport processes.

CONCLUSIONS

The obtained new knowledge can be used to effectively adjust desired drug release mechanisms and, thus, release patterns.

Blends of aqueous polymer dispersions used for pellet coating: Importance of the particle size

Blends of aqueous dispersions of a water-insoluble and an enteric polymer, namely ethyl cellulose:hydroxypropyl methylcellulose acetate succinate (EC:HPMCAS) and ethyl cellulose:methacrylic acid ethyl acrylate copolymer (EC:Eudragit L), were used as coating materials to control theophylline release from matrix pellets. Varying the polymer blend ratio, broad ranges of drug release patterns were obtained at low as well as at high pH. Interestingly, the resulting release profiles were rather similar for both types of blends in 0.1 M HCl, whereas significant differences were observed in phosphate buffer pH 7.4. Surprisingly, drug release at high pH was much slower for EC:HPMCAS blends compared to EC:Eudragit L blends, although HPMCAS leached out more rapidly (and to a higher extent) from the film coatings than Eudragit L. To explain these phenomena and to better understand the underlying drug release mechanisms, thin polymeric films of identical composition as the pellet coatings were prepared and physicochemically characterized before and upon exposure to the release media. Importantly, the polymer particle size was identified to be a very crucial formulation parameter, determining the resulting film coating structure and properties. The Eudragit L particles are much smaller than the HPMCAS particles (nano- vs. micrometer size range) and, thus, more effectively hinder the formation of a continuous and mechanically stable EC network. Consequently, the EC structures remaining after enteric polymer leaching at high pH are mechanically much weaker in the case of Eudragit L. Upon exposure to phosphate buffer, water-filled cracks are formed, through which the drug rapidly diffuses out. In contrast, the EC structures remaining upon HPMCAS leaching are mechanically stronger and drug release is controlled by diffusion through the polymeric remnants.

Polymer blends used for the aqueous coating of solid dosage forms: importance of the type of plasticizer

The aim of this study was to investigate the importance of the type of plasticizer in polymer blends used for the coating of solid dosage forms, comparing a lipophilic and a hydrophilic plasticizer (dibutyl sebacate (DBS) and triethyl citrate (TEC)). In vitro drug release from propranolol hydrochloride (propranolol HCl)-loaded pellets coated with blends of ethyl cellulose (EC) and Eudragit L (100:0, 75:25, 50:50, 25:75 and 0:100 w/w) was investigated at low as well as at high pH. To better understand the underlying mass transport mechanisms, the physicochemical properties of the film coatings (e.g. mechanical resistance, water uptake and dry weight loss behavior) were determined. Interestingly, drug release strongly depended on the type of plasticizer. Importantly, not only the slope but also the shape of the release curves was affected, indicating that the chemical nature of the plasticizer plays a major role for the underlying drug release mechanisms. Diffusion through the intact polymer coatings and/or through water-filled cracks was found to be dominating for the control of drug release. The relative importance of these pathways strongly depended on the polymer blend ratio and type of plasticizer. In contrast to DBS, TEC rapidly leached out of the coatings, resulting in decreasing mechanical resistances of the films and, thus, facilitated crack formation. In addition, the hydrophilicity of the plasticizer significantly affected the water uptake behavior of the film coatings and, hence, changes in the coatings' toughness and drug permeability. Also the relative affinity of the plasticizer to the different polymers was found to be of significance. In contrast to TEC, DBS has a higher affinity to EC than to Eudragit L, resulting in potential redistributions of this plasticizer within the polymeric systems and changes in the release profiles during storage. Importantly, these effects could be avoided with appropriate curing conditions and preparation techniques for the coating dispersions.