ethyl-cellulose and shellac

An in situ forming gel is a dosage form which is promised for site-specific therapy such as periodontal pocket of periodontitis treatment. Ethylcellulose, bleached shellac, and Eudragit RS were applied in this study as a polymeric matrix for in situ forming gel employing N-methyl pyrrolidone (NMP) as solvent. Solutions comprising ethylcellulose, bleached shellac, and Eudragit RS in NMP were evaluated for viscosity, rheology, and rate of water penetration. Ease of administration by injection was determined as the force required to expel polymeric solutions through a needle using texture analyzer. In vitro gel formation and in vitro gel degradation were conducted after injection into phosphate buffer solution pH 6.8. Ethylcellulose, bleached shellac, and Eudragit RS could form the in situ gel, in vitro. Gel viscosity and pH value depended on percentage amount of the polymer, whereas the water diffusion at early period likely relied on types of polymer. Furthermore, the solutions containing higher polymer concentration exhibited the lower degree of degradation. All the preparations were acceptable as injectable dosage forms because the applied force was lower than 50 N. All of them inhibited Staphylococcus aureus, Escherichia coli, Candida albicans, Streptococcus mutans, and Porphyrommonas gingivalis growth owing to antimicrobial activity of NMP which exhibited a potential use for periodontitis treatment. Moreover, the developed systems presented as the solvent exchange induced in situ forming gel and showed capability to be incorporated with the suitable antimicrobial active compounds for periodontitis treatment which should be further studied.

Topics: Acrylic Resins; Anti-Infective Agents; Candida albicans; Cellulose; Diffusion; Drug Delivery Systems; Escherichia coli; Gels; Periodontitis; Polymers; Porphyromonas gingivalis; Pyrrolidinones; Resins, Plant; Solubility; Solvents; Staphylococcus aureus; Streptococcus mutans; Viscosity; Water

The use of naturally derived excipients to develop enteric coatings offers significant advantages over conventional synthetic polymers. Unlike synthetic polymers, they are biodegradable, relatively abundant, have no daily intake limits or restrictions on use for dietary and nutraceutical products. However, little information is available on their dissolution properties under different gastrointestinal conditions and in comparison to each other. This work investigated the gastric resistance properties of commercially available GRAS-based coating technologies. Three coating systems were evaluated: ethyl cellulose+carboxymethyl cellulose (EC-CMC), ethyl cellulose+sodium alginate (EC-Alg) and shellac+sodium alginate (Sh-Alg) combinations. The minimum coating levels were optimized to meet USP pharmacopoeial criteria for delayed release formulations (<10% release after 2h in pH 1.2 followed by >80% release after 45 min of pH change). Theophylline 150 mg tablets were coated with 6.5%, 7%, and 2.75% coating levels of formulations EC-CMC, EC-Alg and Sh-Alg, respectively. In vitro dissolution test revealed a fast release in pH 6.8 for ethyl cellulose based coatings: t80% value of 65 and 45 min for EC-CMC and EC-Alg respectively, while a prolonged drug release from Sh-Alg coating was observed in both pH 6.8 and 7.4 phosphate buffers. However, when more biologically relevant bicarbonate buffer was used, all coatings showed slower drug release. Disintegration test, carried out in both simulated gastric and intestinal fluid, confirmed good mechanical resistance of EC-CMC and EC-Alg coating, and revealed poor durability of the thinner Sh-Alg. Under elevated gastric pH conditions (pH 2, 3 and 4), EC-CMC and EC-Alg coatings were broken after 70, 30, 55 min and after 30, 15, 15 min, respectively, while Sh-Alg coated tablets demonstrated gastric resistance at all pH values. In conclusion, none of the GRAS-grade coatings fully complied with the different biological demands of delayed release coating systems.

Topics: Alginates; Carboxymethylcellulose Sodium; Cellulose; Delayed-Action Preparations; Dietary Supplements; Drug Approval; Gastric Juice; Glucuronic Acid; Hexuronic Acids; Hydrogen-Ion Concentration; Intestinal Secretions; Resins, Plant; Tablets; Theophylline

Powder layering technique was evaluated using laboratory scale centrifugal granulator instrument to prepare extended release pellet dosage form of ketoprofen. Ethyl cellulose and shellac polymers were used for drug layering and extended release coating in the same apparatus. Inert sugar spheres were intermittently treated with drug powder and binding solution. Combination of ethyl cellulose (45cps) and shellac was evaluated as binders at different levels (1:3 ratio, at 6%, 12%, 16% and 21%w/w polymer) for drug loading and for extended release coating (1:3 ratio at 2%, 4% and 7% w/w polymer). Pellets were evaluated for drug release study using paddle apparatus in pH 6.8 Phosphate buffer, 900ml at 100 rpm. Ethyl cellulose and shellac when used as binder during drug layering did not extend the ketoprofen release beyond 4h. However, coating of drug loaded pellets using ethyl cellulose and shellac resulted in extended release profile of ketoprofen for about 10h. Ethyl cellulose coating alone at a level of 3% w/w resulted in extended release profile. Coated pellets were evaluated for sphericity, Hardness-Friability Index and scanning electron microscopy. Scanning electron micrographs of the pellets showed a uniform coating of polymer on the core pellets substantiating the use of centrifugal granulator for extended release coating. Release pattern from the optimized batch was best explained by Higuchi's model. The drug release pattern from the pellets was found to be Non-Fickian anomalous type, involving both diffusion and erosion mechanism. Accelerated stability study of the coated pellets filled in hard gelatin capsule was conducted for 3-month period and observed for the effect on drug release profile.

Topics: Anti-Inflammatory Agents, Non-Steroidal; Capsules; Cellulose; Centrifugation; Delayed-Action Preparations; Drug Compounding; Hardness; Hydrogen-Ion Concentration; Ketoprofen; Resins, Plant

Topics: Cellulose; Drug Packaging; Emulsions; Plant Oils; Resins, Plant; Sunflower Oil

Drug-layered pellets were coated with micronized polymer powders (Eudragit) RS, ethylcellulose, and shellac) by a dry powder coating technique as an alternative to organic- and aqueous-based coatings (Eudragit) RS 30D, Aquacoat) ECD) were investigated. High plasticizer concentrations (40%) and a thermal after-treatment (curing) were necessary for the coalescence of the polymer particles and good film formation. Ethylcellulose required a higher curing temperature and time than Eudragit) RS because of its higher glass transition temperature (133 versus 58 degrees C). A smaller polymer particle size also promoted film formation. In general, pellets coated with polymer powders required higher coating levels to obtain similar drug release patterns as pellets coated with organic polymer solutions and aqueous polymer dispersions.

Topics: Acrylic Resins; Cellulose; Chemistry, Pharmaceutical; Powders; Resins, Plant; Tablets, Enteric-Coated