The metabolism of the anthelmintics clioxanide and resorantel and related compounds in vitro by Moniezia expansa, Ascaris suum and mouse- and sheep-liver enzymes.

1. Clioxanide and related compounds were deacetylated by the cestode Moniezia expansa, the nematode Ascaris suum, by enzymes prepared from these species and by mouse- and sheep-liver homogenates. Deacetylase activity was found in the cytosol of cestode proglottids throughout the strobila, and in the cytosol of nematode intestinal cells and reproductive tract. 2. The O-deacetylases from both helminths showed similar pH optima of about 7.0. Activity was enhanced by Ca2+ and low molecular weight thiols. Cu2+, Cd2+, Hg2+, Zn2+, and La2+ inhibited the deacetylation of clioxanide. 3. Resorantel and clioxanide were not hydrolysed at the amide bond by helminth or mammalian enzymes. 4. Resorantel was hydroxylated by mammalian microsomal enzymes, but helminths did not modify the molecule.