The purpose of this study was to increase the therapeutic index of the antiparasitic drug, trifluralin (TFL), to allow its parenteral administration without the need of toxic solvents. This was achieved by incorporating TFL in liposomes with high loading capacity. These formulations were stable in freeze-dried form during at least one year and in frozen form during at least three months. Therapeutic activity, assessed on a visceral model of infection, showed that TFL liposomes reduced the number of parasites by LIP to one third or one half as compared to negative control and to free TFL, respectively. (C) 2008 Elsevier B.V. All rights reserved. - NATO [941457]; POCTI [CVT/35249/1999]. - NATO Science for Stability Programme III (PO-Infections 941457), POCTI (contract No. CVT/35249/1999). The authors thank Prof Simon Croft from London School of Hygiene & Tropical Medicine for providing the parasite strain and for the supervision on the establishment of the animal models at INETI.