A study on solubilization of poorly soluble drugs by cyclodextrins and micelles: complexation and binding characteristics of sulfamethoxazole and trimethoprim.

The present study is focused on the characterization of solubilization of poorly soluble drugs, that is, sulfamethoxazole (SMX) and trimethoprim (TMP) by cyclodextrins (α-, ß-, and γ-CDs) and anionic surfactant sodium dodecyl sulfate (SDS). The phase solubility diagrams drawn from UV spectral measurements are of the A(L) type and indicate an enhancement of SMX and TMP solubility in the presence of CDs. Complex formation tendency of TMP with CDs followed the order: γ-CD > ß-CD > α-C. However, the complex formation constant values, for SMX-CD system yielded the different affinity and follow the order: ß-CD > γ-CD > α-CD. With taking into consideration of solubilization capacity of SDS micelles, it has been found that the solubility enhancement of TMP is much higher than that of SMX in the presence of SDS micelles. The binding constants of SMX and TMP obtained from the Benesi-Hildebrand equation are also confirmed by the estimated surface properties of SDS, employing the surface tension measurements. In order to elucidate the solubilization characteristics the surface tension measurements were also performed for nonionic surfactant Triton X-100. Polarity of the microenvironment and probable location of SMX and TMP were also discussed in the presence of various organic solvents.

A study on the adsorption characteristics of an amphiphilic phenothiazine drug on activated charcoal in the presence of surfactants.

In this paper the adsorption of amphiphilic phenothiazine drug Thioridazine hydrochloride (THCl) on Activated charcoal (AC) surface was studied in aqueous solutions. The effects of different types of surfactants anionic sodium dodecylsulfate (SDS) and lithium dodecylsulfate (LiDS), cationic cetyltrimethyl ammonium bromide (CTAB) and nonionic TritonX-100 (TX-100) micelles on the adsorption were reported. It was found that the Langmuir isotherm appears to fit the isotherm data better than the Freundlich isotherm. The adsorption of THCl was reduced in the presence of cationic CTAB bearing the same charge as THCl while presence of SDS and LiDs did not change significantly adsorption capacity of THCl on AC except the shape of the isotherm. The presence of TX-100 micelles significantly increased adsorption of THCl on AC. Kinetic measurements showed that the adsorption equilibrium of THCl was attained within 30 min in aqueous media while in the presence of 10mM anionic micelles the adsorption equilibrium of THCl reached the equilibrium almost in 1 min. The kinetics of adsorption in view of three kinetic models i.e. the first-order Lagergren model, the pseudo-second-order model and the intraparticle diffusion model has been discussed. The adsorption rate constants of THCl onto AC in the presence of anionic micelles are higher than in aqueous media for both kinetics models and the second-order model provides the best correlation of data in the absence and presence of micelles. In order to gain further insight into the adsorption mechanism of THCl on AC, association of THCl with surfactants was also studied by absorption spectra. Binding constants of THCl to micelles were calculated by means of Benesi-Hildebrand Equation to provide more precise comparison of the effect of surfactants on the adsorption of THCl.

Interaction of epirubicin HCl with surfactants: effect of NaCl and glucose.

The interaction of an antitumoural drug, Epirubicin HCl, with anionic (sodiumdodecylsulfate; SDS), cationic (cetyltrimethylammonium bromide; CTAB), and nonionic (t-octylphenoxypolyethoxyethanol; TX-100, polyoxyethylenesorbitanmonolaurate; Tween 20) surfactants has been studied by absorption spectra as a function of surfactant concentration ranging from the premicellar to postmicellar region. At the concentrations below the critical micelle concentration (CMC), the equilibrium complex formation constant between Epirubicin cations and SDS anions has been determined by Job's method. Above the CMC, binding constant (K(b)) of Epirubicin to various types of micelles has been calculated by means of the Benesi-Hildebrand Equation. The nonionic surfactant micelles showed stronger interaction than the ionic SDS micelles, and the binding tendency of Epirubicin followed the order: Tween 20 > TX-100 > SDS. Binding of Epirubicin also has been studied in the presence of NaCl and glucose because it is administered to patients intravenously in 0.9% NaCl or 5% glucose solution. The additives have been observed to affect the CMC of the surfactants and the Epirubicin-micelle binding constant appreciably. The presence of NaCl and glucose lowered the CMC of all the surfactants studied. The binding constant of Epirubicin decreased in the presence of NaCl but increased in the presence of glucose. The equilibrium complex formation constant between Epirubicin and SDS decreased in the presence of NaCl compared with purely aqueous media.

Spectral studies of safranin-O in different surfactant solutions.

The interaction of Safranin-O (SO), a cationic dye, with various surfactants viz., anionics; Sodiumdodecylsulfate (SDS) and Sodiumdodecylsulfonate (SDSo), nonionics; polyoxyethylenesorbitanmonolaurate (Tween 20) and polyoxyethylenedodecylether (Brij 35), cationic; Dodecyltrimethylammoniumbromide (DTAB) and zwitterionic; Laurylsulfobetaine (LSB) was studied spectrophotometrically as a function of surfactant concentration ranging from premicellar to postmicellar region in aqueous media in the absence and presence of cosolvents. The binding constants (K(b)) and fraction of bound SO to micelles (f), were calculated by means of Benesi-Hildebrand Equation. The binding tendency of SO to micelles followed the order as; Tween 20>Brij 35>SDS>SDSo>LSB. The presence of cosolvents, such as Methanol, Dimethylformamide (DMFA) and 1,4 Dioxan (DX) at various volume percentages, increased the CMC of both SDS and Tween 20 and at a certain concentration totally inhibited the micellization. The binding of SO to micelles decreased as the concentration of the cosolvents increased. This inhibitory effect of cosolvents on binding of SO to micelles followed the order as; Methanol>DMFA>DX.