The level of synergism encountered with the two systems differed, Cremophor EL + ethanol exhibiting a larger rate. Based on the solubilizing power of the solvent Veliparib solubility dmso systems comprising Cremophor EL in combination with ethanol or PEG200 or ethanol and PEG200 it was concluded that the combination of Cremophor EL and ethanol was the most effective solvent system for solubilizing MPTS. Furthermore, this system showed a marked synergistic solubilizing effect at 75% ethanol content. It was the aim of the research to develop a solvent system that comprises excipients in concentrations as low as possible while still exerting
substantial solubilizing power, therefore, the synergistic solubilizing effect of Cremophor EL and ethanol were further studied. The solubility of MPTS was determined in Cremophor EL and ethanol combinations where the concentration of
the co-solvent was decreased to 62.5% and 50%. Solubility of MPTS in such systems is presented together with the solubility values of Cremophor EL + 75% ethanol (for the ease of comparison) in Fig. 5. Results proved that the synergistic solubilizing effect encountered at 75% was also detected at 62.5% and 50% ethanol content (Table 4). The possible explanation for the solubility enhancing effect of the co-solvent/surfactant/water systems is the following: this website Surfactants form micelles above their critical micelle concentration, but the addition co-solvents, such as ethanol, increase the cmc. Furthermore, above a certain concentration (25% for polyoxyethylene (23)
lauryl alcohol, a non-ionic surfactant) co-solvents inhibit micelle formation of the surfactants (Becher, 1965). The concentration of ethanol in the tested solvents is well above the referenced concentration, thus surfactants do not form micelles in the applied solubility enhancing systems. Therefore, the solubilizing effect of the surfactant/co-solvent/water mixture does not depend on the number most of micelles. To rule out the solubilizing effect based solely on the change in the polarity of the solvents their dielectric constant was tested. It was seen that the addition of Cremophor EL increased the dielectric constant of the solvents compared to that of water/ethanol systems (Table 5). Since a decrease in dielectric constant increased the solubility of MPTS in water/ethanol systems it was concluded that an increase in the dielectric constant should have decreased its solubility. The opposite phenomenon was encountered thus it was concluded that the solubilizing effect of the solvent systems is probably due to the formation of a mixture with a determined ratio of surfactants, ethanol and active ingredient and not due to the change in the polarity of the solution.