The antischistosomal effect of the enantiomers of praziquantel and three praziquantel derivatives were investigated in mice infected with Schistosoma japonicum. The results of the experiments showed that the worm reduction rates in the groups treated with levo-pra-ziquantel in a single dosage of 250mg/kg or 4l7mg/kg

intragastrically were 50.0% and 72.0%

respectively whereas the average number of worms still alive per mouse in the groups treated with dextro-praziquantel at the same single dosage regimes

250mg/kg or 4l7mg/ kg

intragastrically were not significantly different from that of control group.The three praziquantel derivatives

S-01

S-02 and S-04

in a dosage regime of 0.64 mmol/kg

qd x 3d were screened in infected mice but none of them showed significant antischistosomal effect