Abstract Nanoparticles of polyisohexylcyanoacrylate with bound primaquine were prepared by an emulsion polymerization method and an i.v. formulation was obtained after freeze-drying. Such formulation is intended for drug targeting in visceral leishmaniasis. Drug binding seemed largely dependent on pH and formulation conditions were optimized to obtain a polymeric colloidal suspension containing particles in the 200–250 nm size range and 80–90% drug binding (final content of 10 mg of drug per vial). Aspects such as polymer-drug interaction, in vitro drug release and physicochemical stability were studied. A significant reduction in acute toxicity was demonstrated by using the targeted formulation in NMRI mice.