Solubilizing Potential of Ionic, Zwitterionic and Nonionic Surfactants Towards Water Insoluble Drug Flurbiprofen

Quite a high percentage of newly discovered drugs are discarded due to their low aqueous solubility and variable bioavailability. Therefore, it is necessary to explore new methodologies for increasing the aqueous solubility of such drugs. Several procedures have been proposed for this purpose, including salt formation, particle size reduction or using surfactants. In this report, we have improved the aqueous solubility of flurbiprofen by employing aqueous solution of anionic (SDS, SDBS), cationic (DTAB, CTAB, TTAB), non-ionic (Triton X-100 and Triton X-114 and DDAO) and zwitterionic DDAPS surfactants. It is concluded that all of the surfactants increased the solubility of flurbiprofen which increased with the increasing surfactant concentration. The reason behind such a trend was that the drug is partitioned between micelles and the aqueous phase. An increase in aqueous solubility of the drug was correlated with the (molar) solubilization ratio (χ), partition coefficient of drug (KM) between micelle and water, binding constant (K1) and standard state Gibbs energy of solubilization (\(\Delta G_{\text{s}}^{\text{o}}\)) of the drug in the micelles. The order of drug solubilization in nonionic and zwitterionic surfactants was found as Triton X-114 > Triton X-100 > DDAO > DDAPS. In the case of anionic surfactants, it was noted as SDBS > SDS, whereas cationic surfactants solubilized the drug in the order of CTAB > TTAB > DTAB. The differences in χ and log10KM are attributed to the structural features of the surfactants. The aggregation number, HLB, core volume of micelles and electrostatic interaction between drug and micelles play important roles in solubilization of drugs in micellar solutions. The nonionic surfactants proved to be better, due to their low critical micelle concentrations higher solubilization capability and nontoxic nature; they were also found to have better drug release profiles.