To study the possibility of increasing the solubility of the substance triclabendazole (TCB), we used the technology of mechanochemical modification of TCB using water-soluble polymers, polyvinylpyrrolidone (PVP) and arabinogalactan (AG) from Siberian larch Larix sibirica in particular. After joint machining of TCB with polymers (PVP, AG) in a LE-101 ball mill (made in Hungary), free flowing powder dispersions with an increased solubility (more than 50 times as compared to the original substance TCB) were obtained. This result was explained by the formation of intermolecular complexes of the type of hydrogen bond between the characteristic groups of TCB and polymers, which was confirmed by the data of IR-spectral studies. Tests of intermolecular complexes on spontaneously fasciola-infected sheep have shown high efficiency. As a result of the research, it was found that the complex of TCB: AG composition (1:9), which we named “triclafascid”, possesses a number of positive attributes in comparison with the substance of TCB and provides high fasciolocid and economic efficacy, and safety of use by reducing the therapeutic dose. Inclusion of arabinogalactan, which has hepatoprotective, antimutagenic, mitogenic, gastroprotective properties, in the preparation, made it possible to reduce the toxicity of the preparation proposed for practice. It was shown that residual amounts of TCB and its metabolites were not detected in tissues and organs on the 14th day of the experiment with triclafascid, which indicates the possibility of slaughtering an animal and using meat 14 days after using the drug. The drug has good solubility, bioavailability to helminthes, is non-toxic, and increases antihelminthic and economic efficiency. The obtained results confirmed the previously obtained data on the prospects of an innovative approach to improve the quality indicators of anthelmintic drugs and to obtain effective drugs for veterinary medicine.