A soluble complex of an insoluble drug, exemplified by Rafoxanide is formed with polyvinylpyrrolidone and water. The complex is formed by combining the insoluble drug and polyvinylpyrrolidone in a suitable water miscible organic solvent, preferably acetone or glycerolformal, and water. The complex is formed in situ. The solvent may be removed, if desired, and the complex remains in aqueous solution. The aqueous solution is then suitable for injection and may be used to treat fasciola or liver fluke infections.