RESUMEN
This study is an investigation of the physicochemical interaction of Losartan potassium (LST K), an angiotensin-II receptor (type AT1) antagonist, with micelles of triton X, a nonionic surfactant. The effect of micelles on the spectral properties of LSTK was monitored on at pH 7.4 and at room temperature. The spectrum of LST K showed gradual and progressive bathochromic and hypochromic shift in presence of increasing concentrations of triton X 100. The binding constant Kb of LST K to triton X 100 micelles was calculated using the differential absorbance at λ = 225 nm& was found to be 4.13 ± 0.35 ×105 mol-1 L. By using pseudo-phase model, the partition coefficient between the bulk water and Triton X 100 micelles, Kx, was calculated from both differential absorbance Δ A225, Kx = 2.26 ±0.12 x105 mol-1 L. The binding of LST K to Triton X 100 micelles implied a shift in drug acidity constant (Δ pKa = 0.8).