Tricyclic drugs as microemulsion cosurfactants

To assess the possibility of using drugs as cosurfactants in microemulsions, o/w systems were prepared, containing 1-decanol/1-dodecanol as oil, water, Cremophor EL or Epikuron 200 (soybean lecithin) as surfactant and one of eight phenothiazines (chlorpromazine, aminopromazine, promazine, promethazine, triflupromazine, trifluperazine, levomepromazine, dietazine) and six other tricyclic amines (amitriptyline, clomipramine, desipramine, dimethacrine, imipramine, nortriptyline) as cosurfactant. Phase diagrams of quaternary systems with Cremophor EL and the selected drugs were explored and the areas of existence of stable microemulsions identified. Not all the drugs were able to give clear isotropic systems at room temperature; trifluperazine failed to form microemulsious. For systems containing Epikuron 200, the minimum amount of drug required to form a microemulsion was determined. Transparent systems were obtained with all examined drugs; the percentages of cosurfactant were relatively low and quite similar for all drugs.