methylcellulose and methylparaben

We designed ophthalmic formulations containing dexamethasone-loaded solid nanoparticles (DEX

Topics: Animals; Cell Line, Transformed; Cornea; Dexamethasone; Drug Compounding; Drug Delivery Systems; Escherichia coli; Humans; Methylcellulose; Microbial Sensitivity Tests; Nanoparticles; Ophthalmic Solutions; Parabens; Permeability; Rabbits; Rats

Among thymol, carvacrol, citronellal, eugenol and terpinen-4-ol, thymol showed the highest antibacterial activity against Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa. Thymol was then encapsulated into water dispersible submicron sized ethylcellulose/methylcellulose spheres, attaining the relatively high thymol loading level of 43.53% (weight of encapsulated thymol to weight of the thymol-loaded spheres). When tested against the same three bacterial strains, the encapsulated thymol gave comparable minimal inhibition concentration (MIC) and minimal bactericidal concentration (MBC) values to the unencapsulated compound while mostly showing lower MIC and MBC values than the conventionally used preservative, methyl-p-hydroxybenzoate (methylparaben). The use of encapsulated thymol at 0.078, 0.156 and 0.625 mg ml(-1) (0.52, 1.04 and 4.16 mmol(-1), respectively) in cosmetic lotion formulations provided total suppression of viable E. coli, S. aureus and P. aeruginosa growth (all initially seeded at 10(5) cfu ml(-1)), respectively, over the three month test period, whereas unencapsulated thymol showed effective suppression for only 2-4 weeks. Effective bacterial suppression by encapsulated thymol was also observed when used in cream and aqueous gel cosmetic formulations.

Topics: Anti-Bacterial Agents; Cellulose; Cosmetics; Escherichia coli; Excipients; Gels; Methylcellulose; Microbial Sensitivity Tests; Nanospheres; Parabens; Particle Size; Preservatives, Pharmaceutical; Pseudomonas aeruginosa; Skin Cream; Staphylococcus aureus; Thymol; Time Factors

This study investigates the effect of the chemical heterogeneity of hydroxypropyl methylcellulose (HPMC) on the release of model drug substances from hydrophilic matrix tablets. The hypothesis was that the release of drug substances could be influenced by possible interactions with HPMC batches having different chemical heterogeneity. The cloud point of the most heterogeneous batch was more affected by the model drug substances, methylparaben and butylparaben, and most by butylparaben with the lowest solubility. The different clouding behaviour was explained by the heterogeneously substituted batches being more associative and the more lipophilic butylparaben being able to interact more efficiently with the hydrophobic HPMC transient crosslinks that formed. Interestingly, tablet compositions of the heterogeneously substituted HPMC batches released the more soluble methylparaben at lower rates than butylparaben. The explanation is that the hydrophobic HPMC interactions with butylparaben made the gel of the tablet less hydrated and more fragile and therefore more affected by erosional stresses. In contrast, drug release from compositions consisting of the more homogeneously substituted batches was affected to a minor extent by the drugs and was very robust within the experimental variations. The present study thus reveals that there can be variability in drug release depending on the lipophilicity of the drug and the substituent heterogeneity of the HPMC used.

Topics: Chemical Phenomena; Delayed-Action Preparations; Drug Compounding; Excipients; Gels; Hydrophobic and Hydrophilic Interactions; Hypromellose Derivatives; Kinetics; Methylcellulose; Parabens; Pharmaceutical Preparations; Reproducibility of Results; Solubility; Tablets; Transition Temperature; Viscosity

The release of a model drug substance, methylparaben, was studied in matrix tablets composed of hydroxypropyl methylcellulose (HPMC) batches of the USP 2208 grade that had different chemical compositions. It was found that chemically heterogeneous HPMC batches with longer sections of low substituted regions and lower hydroxypropoxy content facilitated the formation of reversible gel structures at a temperature as low as 37°C. Most importantly, these structures were shown to affect the release of the drug from matrix tablets, where the drug release decreased with increased heterogeneity and a difference in T80 values of 7h was observed between the compositions. This could be explained by the much lower erosion rate of the heterogeneous HPMC batches, which decreased the drug release rate and also released the drug with a more diffusion based release mechanism compared to the less heterogeneous batches. It can therefore be concluded that the drug release from matrix tablets is very sensitive to variations in the chemical heterogeneity of HPMC.

Topics: Chemistry, Pharmaceutical; Drug Carriers; Hypromellose Derivatives; Methylcellulose; Molecular Weight; Parabens; Solubility; Tablets; Temperature; Viscosity

This study developed and examined the characterization of Benzidamine hydrochloride (BNZ) bioadhesive gels as platforms for oral ulcer treatments. Bioadhesive gels were prepared with four different hydroxypropylmethylcellulose (HPMC) types (E5, E15, E50 and K100M) with different ratios. Each formulation was characterized in terms of drug release, rheological, mechanical properties and adhesion to a buccal bovine mucosa. Drug release was significantly decreased as the concentration and individual viscosity of each polymeric component increased due to improved viscosity of the gel formulations. The amount of drug released for the formulations ranged from 0.76 +/- 0.07 and 1.14 +/- 0.01 (mg/cm2 +/- SD). Formulations exhibited pseudoplastic flow and all formulations, increasing the concentration of HPMC content significantly raised storage modulus (G'), loss modulus (G''), dynamic viscosity (eta') at 37 degrees C. Increasing concentration of each polymeric component also significantly improved the hardness, compressibility, adhesiveness, cohesiveness and mucoadhesion but decreased the elasticity of the gel formulations. All formulations showed non-Fickian diffusion due to the relaxation and swelling of the polymers with water. In conclusion, the formulations studied showed a wide range of mechanical and drug diffusion characteristics. On the basis of the obtained data, the bioadhesive gel formulation which was prepared with 2.5% HPMC K 100M was determined as the most appropriate formulation for buccal application in means of possessing suitable mechanical properties, exhibiting high cohesion and bioadhesion.

Topics: Adhesiveness; Administration, Buccal; Animals; Benzydamine; Biological Availability; Cattle; Compressive Strength; Drug Delivery Systems; Elasticity; Gels; Hardness; Humans; Hypromellose Derivatives; Mechanical Phenomena; Methylcellulose; Mouth Mucosa; Oral Ulcer; Parabens; Rheology; Viscoelastic Substances

The aim of the study was to provide a controlled release system, which could be used for the oral administration of highly water-insoluble drugs. Pellets have been prepared by extrusion/spheronization containing two model drugs (methyl and propyl parabens) of low water solubility. One type of pellets contained the drugs mixed with lactose and microcrystalline cellulose (MCC) and the other types of pellets contained the model drugs dissolved in a self-emulsifying system (4.8%) consisting of equal parts of mono-diglycerides and polysorbate 80 and MCC. Pellets of all types in the same size fraction (1.4-2.0 mm) were coated to different levels of weight gain, with ethylcellulose, talc and glycerol. A sample of pellets containing methyl parabens in the self-emulsifying system was pre-coated with a film of hydroxypropylmethyl cellulose from an aqueous solution and then coated as above. Dissolution experiments established that the presence of the self-emulsifying system enhanced the drug release of both model drugs and that the film coating considerably reduced the drug release from pellets made with just water, lactose and MCC. The coating reduced the drug release from the pellets containing the self-emulsifying system to a lesser extent but in relation to the quantity of coat applied to the pellets. The application of a sub-coating of hydroxypropylmethyl cellulose was able to reduce the release rate of methyl parabens self-emulsifying system ethyl cellulose coated pellets. Thus, the formulation approach offers the possibility of formulating and controlling the in vitro release of water-insoluble drugs from solid oral dosage forms.

Topics: Capsules; Cellulose; Chemistry, Pharmaceutical; Delayed-Action Preparations; Diglycerides; Emulsions; Excipients; Hypromellose Derivatives; Lactose; Methylcellulose; Monoglycerides; Parabens; Particle Size; Pharmaceutical Preparations; Polysorbates; Solubility; Technology, Pharmaceutical; Time Factors; Water

The stability of captopril in several extemporaneously prepared oral liquid formulations was studied. Captopril 1-mg/mL oral liquid formulations were prepared from either powder or tablets in two grades of water, syrup, methylcellulose, and edetate disodium. The liquids were stored at 5 degrees C in amber glass containers, and samples were removed at intervals up to 30 days for assay of captopril concentration by stability-indicating high-performance liquid chromatography. The pH of the formulations remained fairly stable for 30 days. In general, captopril was more stable in formulations containing captopril from tablets than from powder. Captopril in formulations in which the only vehicle was highly purified water was slightly but not significantly more stable than in formulations made with sterile water for irrigation. Formulations made with undiluted syrup were more stable than formulations in which water was used to dilute syrup or formulations containing methylcellulose. The formulations containing edetate disodium were much more stable than those that lacked this component. The stability of captopril 1 mg/mL in oral liquid formulations was influenced by the captopril source (tablets versus powder) and by the presence of syrup, methylcellulose, and edetate disodium. Captopril in a preparation made with tablets and undiluted syrup was stable for 30 days at 5 degrees C, and the formulation should be palatable.

Topics: Captopril; Drug Stability; Hydrogen-Ion Concentration; Methylcellulose; Parabens; Preservatives, Pharmaceutical; Temperature

Topics: Antifungal Agents; Aspergillus; Benzoates; Chemistry, Pharmaceutical; Dialysis; Esters; Glycols; Methylcellulose; Parabens; Polyethylene Glycols; Polymers; Preservatives, Pharmaceutical; Renal Dialysis; Research; Rhizopus; Solubility