Formulation and physicochemical evaluation of diclofenac sodium chewable tablets

Taste masked diclofenac sodium, by three techniques, namely microencapsulation with ethylcellulose, ethylcellulose pan coating and 'inclusion complexation with beta-cyclodextrin followed by coating with an aqueous dispersion of ethylcellulose [Aquacoat], was formulated into chewable tablets. After several trials, three formulae, one for each type of the treated diclofenac sodium, were selected. The chosen three formulae were directly compressed into 10 mm diameter flat tablets containing 25 mg of diclofenac sodium and weighing about 600 mg. The produced tablets were evaluated with regard to their taste profile in addition to uniformity of dosage, friability, hardness and dissolution. The obtained results indicated that the three different batches of diclofenac sodium chewable tablets had good to excellent taste except for that based on diclofenac sodium-beta-cyclodextrin inclusion complex. The three batches complied with the pharmacopoeal [USP XXIV] requirements with regard to uniformity of dosage and friability and they showed reasonable hardness values. With regard to the in vitro release profile [in phosphate I buffer pH 7.4], two of the three chewable tablet batches showed fast release profiles, whereas the batch based on diclofenac sodium microcapsulcs showed a relatively slow release pattern

Preparation of metronidazole microcapsules for sustained delivery

Metronidazole is widely used in the treatment of both intestinal and extra-intestinal amebiasis. However, conventional administration usually shows unpleasant taste, nausea, epigastric distress and stomatitis. To avoid these unwanted side effects, a multiple-emulsification technique was used in the preparation of metronidazole microsphere using a mixture of ethyl cellulose [EC] and methyl cellulose [MC] as a matrix. Methyl cellulose was added to enhance drugs release from ethyl cellulose matrix, because the drug has a relatively long t 1/2 [about 16 to 12 hours]. Particles size analysis results showed that the extent of size distribution was reduced with enhancing the stirring rate and the microcapsule size was reduced as the emulsifier concentration was increased up to 2% w/w. This was the optimum concentration of the emulsifiers required for the multiple emulsification. The results, also, showed no correlation between the HLB of the used emulsifiers and the microcapsule size. The in vitro drug release was studied and prolonged release were obtained where 80-90% of metronidazole was released within 6-8 hours depending on drug: polymer ratio. Further, an increase in the amount of water-soluble MC increased the drug released rate

Preparation of sustained release theophylline by using different techniques

Sustained release theophylline has been prepared by using the solid dispersion, wet granulation and microencapsulation techniques. Physical mixture of the drug and ethyl-cellulose showed complete drug release within 80 minutes, a fact that excludes their application in controlling drug release. Co-precipitates of theophylline in ethylcellulose [EC] were prepared using different concentrations of the polymer dissolved in ethanol or in ethanol-chloroform mixture [1:1]. The dissolution studies showed that the concentration of the polymer in the system is a determining factor in controlling the release rate of the drug. The type of solvent also has a marked effect on the rate and pattern of theophylline release. Within half an hour, 32.4% of the drug was released from the solid dispersion prepared using ethanol alone and T50 was 45 minutes, while only 20.9% of the drug was released from the solid dispersion prepared using a mixture of solvents and T50 was 180 minutes. The presence of polyvinyl-pyrrolidone [PVP], modified the release pattern of theophylline. The results showed that by increasing the PVP/EC ratio, the rate of theophylline release increased. Theophylline granules were prepared using different amounts of microcrystalline cellulose, cellulose acetate phthalate and ethylcellulose as fillers. The obtained dissolution results showed that altering the Avicel-ethylcellulose ratio affected the release rate markedly. Theophylline microcapsules showed initial rapid release where about 40% of the core was released within one hour. The obtained results revealed that co-evaporates could be considered as an ideal technique for preparing medicines required for sustained release preparations. This is due to the homogeneous drug distribution and the uniform drug release in comparison to the other techniques used in this study

influence of certain additives and preparative conditions on surface adhesion of ethylcellulose microcapsules containing isoniazid

The microcapsules described in this study were prepared by the phase separation technique induced by the addition of nonsolvent. The obtained results revealed that despite of the vigorous stirring, this procedure is not suitable for forming coacervate droplets and the formation of small or perfect microcapsules becomes unreproducible due to surface adhesion during the tacky stage of the microcapsule formation. The microcapsules that resulted consisted of aggregates and not individual entities. To lessen the tendency to surface adhesion between these coacervate droplets, different amounts of cholesterol [CH], Polyisobutylene [PIB] and talc were used as additives to help in the preparation of fine or individual microcapsules. The addition of cholesterol or polyisobutylene was found to reduce the aggregation of the formed microcapsules, while talc did not show any significant effect. The formation of aggregated microcapsules were also minimized by choosing the appropriate core: wall ratio, stirring speed, solvent, initial core size and method of preparation. The emulsion-induction technique used for the preparation of microcapsules allowed the optimal formation of coacervate droplets and produced fine microcapsules. Microcapsules prepared by the emulsion induction technique showed smaller mean particle diameter [200 micro. m] in comparison to that prepared by the conventional method of preparation [501 microm]. Microcapsules prepared in the presence of cholesterol showed a narrow particle size distribution curves. These microcapsules were subjected to dissolution studies. The obtained results showed that the drug release was prolonged and the presence of cholesterol also delayed the drug release. For all the microcapsules studied, drug release occurs by a diffusion controlled process as described by Higuchi for the release of drug from insoluble matrix

Preparation of albumin microspheres by the emulsification technique

Egg albumin microspheres have been prepared by the emulsification procedure. The most important variables in the production of albumin microspheres have been studied. Increasing the albumin concentration gave rise to an increase in both the mean size and the size distribution of the prepared microsphere due to its effect on the viscosity of the dispersed phase. In order to obtain larger microspheres, relative low stirring speeds have been chosen. Heat was used to denature the albumin, rapid heating seemed to facilitate aggregation of the formed microspheres. In an attempt to control the particle size of the dispersed phase, different concentrations of sorbitan trioleate have been used during the preparation. The presence of excess concentration of drug on the surface of the microspheres resulted in a burst effect for drug release in 0.1 N HCl with up to 25% drug released in 5 minutes. Spermaceti and beeswaxes were included in an effort to slow drug release and to eliminate the initial burst effect. Drug release was found to vary with type and level of wax and the degree of thermal treatment. In vitro drug release profiles were evaluated for the untreated and treated spheres at room temperature and at 80C. In general, the simple incorporation of wax into the microspheres did not provide the desired controlled release of the drug. Thermal treatment of the albumin microspheres, however, resulted in a products which behaved in a different manner during dissolution testing and in general, provided slower release