Surface and Bulk Properties of Two Amphiphilic Phenothiazine Drugs in Different Aqueous Media

Surface behavior and bulk properties of two phenothiazine drugs, fluphenazine and trifluoperazine dihydrochlorides, are reported. Surface activity studies for both amphiphilic drugs were carried out in aqueous solutions at 20 °C by surface tension measurements. The volumetric and compressibility properties of the drugs were derived from density and ultrasound velocity measurements. Critical concentrations were determined by surface tension and ultrasound data. The experiments were realized in aqueous and buffered (pH 3.0, 5.5, and 9.2) media at 20 °C. The buffered media were chosen below and above the different pKa's that the drug molecules present (pKa1 and pKa2 of 3.90 and 8.10, respectively).