Interaction of antidepressant drug with surfactant mixture in various compositions: effect of electrolyte and urea

The purpose of the current work is to explore the interactions between antidepressant drug amitriptyline hydrochloride (AMT, an amphiphilic) and Triton-165 (TX-165, a nonionic surfactant) by applying surface tension, and UV–visible spectroscopy methods. In diverse solvents (aqueous system/50 mmol kg⁻¹ NaCl/500 mmol kg⁻¹ urea), experimental results using the surface tension technique revealed non-ideal behavior along with attractive/synergistic interactions at interface among the AMT drug and TX-165 mixed systems. As contrasted with aqueous system, NaCl media boosted the interfacial properties, resulting in increased synergism/attractive interaction between ingredients (AMT and TX-165), while urea media had the opposite effect. Numerous interfacial parameters such as surface excess concentration (Γ_max), surfactant composition at mixed monolayer ( \(X_{1}^{{\upsigma }}\) $X_1^{\mathrm{\sigma }}$ ), interaction parameters (β^σ) activity coefficient [f₁^σ (TX-165) and f₂^σ (AMT)], and minimum area per molecule ( \(A_{{{\text{min}}}}\) $A_{\text{min}}$ ) were assessed and illustrated in detail. Interaction parameters (β^σ) at surface were attained negative in each case revealing the attractive/synergism among the constituents. It was found that the Gibbs energy of adsorption ( \(\Delta G_{{{\text{ads}}}}^{ \circ } )\) $\mathrm{\Delta }{G}_{\text{ads}}^{\circ })$ throughout all utilized solvent was negative, which indicates spontaneity in the adsorption phenomena. AMT + TX-165 mixtures show synergistic or attractive interactions and non-ideal mixing behaviors at surface depending on mixture composition. In addition, UV–visible analysis detected peak shifts and a surge in absorbance during the interaction of TX-165 with TX-165. It was suggested in the current study that TX-165 surfactant could be used for effective drug delivery of antidepressants.