Micellization properties of antihistaminic drug diphenhydramine.HCl in aqueous electrolytic solution: Conductometric and spectroscopic studies

The empathetic knowledge about the drug-electrolyte interactions is imperative in understanding the pharmacology and pharmacokinetics of drug. Therefore in the present paper, the effect of aqueous electrolytic solutions on the micellization behavior of an antihistaminic drug diphenhydramine.HCl (DPH) has been extensively examined through conductometric, fluorometric and spectrophotometric studies. The effect of various electrolytes occurring in the body fluid on self-association behavior of DPH was evaluated in terms of critical micelle concentration (CMC) obtained by conductivity and spectroscopic data over the temperature range (298.15–313.15) K with the regular interval of 5 K. The so obtained CMC data is used to calculate standard Gibbs free energy change of micellization (ΔGmo), entropy change of micellization (ΔGmo), and enthalpy change of micellization (ΔHmo), for the aforesaid drug in the presence of various electrolytes. The standard thermodynamic parameters of micellization were used to examine various solute-solvent interactions existing in drug-electrolyte-water system under discussion. Various thermodynamic parameters viz. ΔGmo, ΔHmo, and ΔGmo found to support the fact that electrolytes favor the association behavior of the DPH, which is further validated by pseudo-phase model.