The metabolism of niclosamide and related compounds by Moniezia expansa, Ascaris lumbricoides var suum, and mouse- and sheep-liver enzymes.

1. Niclosamide and related nitro compounds were reduced to the corresponding amines by Moniezia expansa, Ascaris lumbricoides var suum and by enzymes prepared from these species and by mouse and sheep liver homogenates. The reduction of niclosamide by the helminths required as cofactors NADH2 and glutathione, but was inhibited 50% by 2 X 10(-7) M allopurinol. 2. Unlike benzanilide, niclosamide was not hydrolysed by either the helminths, or the mammalian liver preparations. Rates of hydrolysis of compounds related to niclosamide indicate that niclosamide was not hydrolysed because substituents in both benzene rings ortho to the amide bond sterically hinder the hydrolase. 3. Hydrolysis of benzanilide and related compounds was inhibited by anthelmintic organophosphates.