Takayuki Ohwaki

Improvement of the stability of water-in-oil-in-water multiple emulsions by the addition of surfactants in the internal aqueous phase of the emulsions

Abstract In order to improve the stability of w/o/w emulsions, an attempt was made to elucidate the influence of addition of hydrophilic surfactants into the internal aqueous compartment of the emulsion, on the breakdown of the suspending vesicular globules of w/o/w emulsion, the changes in diameter of the internal aqueous compartments and of the suspending vesicular globules of w/o/w emulsion, as compared with emulsions without additives and with addition of sodium chloride. It was also attempted to measure the effect of addition of hydrophilic surfactant to the three different phases on the stability of w/o/w emulsions. The stability of diluted w/o/w emulsions with a large difference in osmolarity between the internal aqueous compartments and the external aqueous phase was also tested, w/o/w emulsions were prepared by the two-step emulsification procedure. New coccine was employed as a marker to check the yield of formation and the breakdown of the w/o/w emulsions. Sodium octanesulfonate was used as an additive in the internal aqueous compartment of the w/o/w emulsions as well as sodium chloride. Polyoxyethylene (20) sorbitan monooleate was used as an additive to the three different phases of the emulsions. The stability of w/o/w emulsions, as determined by coalescence of internal aqueous compartments and their increase in size by the influx of water to the internal aqueous compartment from the external aqueous phase, was improved by the addition of hydrophilic surfactant in the internal aqueous compartments of the emulsions. This was observed even under the condition of a large difference in osmolarity between the internal aqueous compartments and the external aqueous phase, and was affected by the concentration of hydrophilic surfactant. The addition of sodium chloride to the internal aqueous compartments and of hydrophilic surfactant to the external aqueous phase did not improve the stability of w/o/w emulsions. Only the addition of hydrophilic surfactant into the internal aqueous compartments was demonstrated to inhibit both coalescence of internal aqueous compartments and influx of water to the internal aqueous compartment from the external aqueous phase. On the other hand, the addition of hydrophilic surfactant into the oil phase was observed not to inhibit coalescence but water influx.

Preparation of a novel type of controlled-release carrier and evaluation of drug release from the matrix tablet and its physical properties

Abstract Solved mixtures of hydrogels (SMH), composed of hydroxypropylcellulose (HPC), a pseudo-hydrogel, and ethylcellulose, a water-insoluble polymer, were prepared by solvent evaporation. Phenylpropanolamine hydrochloride was used as a model drug. The amount of drug released from a matrix tablet containing SMH powder and the drug increased with decreasing weight fraction of HPC (WFH) in SMH. SMH showed improved properties compared to HPC alone, for example, flowability and hydroscopicity. These properties increased with decreasing WFH. The sorption apparatus described in this study is capable of an immediate, sensitive and accurate response to initial moisture sorption. The kinetics of moisture sorption measurement using this apparatus is useful for a preliminary study.

Improvement of the formation percentage of water-in-oil-in-water multiple emulsion by the addition of surfactants in the internal aqueous phase of the emulsion

Abstract In order to improve the formation percentage of w/o/w emulsions, experiments were conducted in order to elucidate the influence of the addition of various kinds of surfactants in the internal aqueous phase of the emulsion, the formation percentage of w/o/w emulsion as compared with that without additives, and with sodium chloride or sorbitol. Several physico-chemical properties of intact w/o/w emulsion or each phase, such as the osmolarity, interfacial tension and viscosity, were investigated in order to determine the governing factor in improving the formation percentage of w/o/w emulsion. w/o/w emulsion was prepared via a two-step emulsification procedure. New coccine was employed as a marker to evaluate the formation percentage of w/o/w emulsion. Sodium alkylsulfonate, sodium alkylsulfate, sodium alkylcarbonate and polyoxyethylene (20) sorbitan monooleate were used as additives in the internal aqueous phase of w/o/w emulsion as well as sodium chloride and sorbitol. The formation percentage of w/o/w emulsion was improved by increasing the concentration of the additives, viz., various kinds of surfactants in the internal aqueous phase of the emulsion, as well as sodium chloride or sorbitol. This could be attributed to a decrease in interfacial tension between the internal aqueous phase of the w/o/w emulsion and the oily phase of the emulsion.

Effect of physical properties of orally disintegrating tablets on disintegration time as determined by a new apparatus

The purpose of this study was to evaluate the usefulness of a new disintegration testing apparatus, ODT-101, and to investigate the effects of the physical properties of orally disintegrating tablets (ODTs) on their disintegration time. We prepared ODTs of different weights and diameters at different tabletting pressures using an excipient Ludiflash. Disintegration times were measured by human sensory evaluation and using the ODT-101. The disintegration time measured by the ODT-101 was found to be in good agreement with that measured in the oral cavity. Disintegration time was found to be a function of porosity and weight, regardless of ODT shape, and to be an exponential function of the hardness of the ODT. In conclusion, ODT-101 testing is accurate enough to be a substitute for sensory evaluation and the hardness of the ODT is a good marker for disintegration time.