Chemotherapy of
trematode infections has been studied intensively in the past. The compounds so far used for the treatment of those
parasitic infections were not satisfactory, however, because of their poor tolerability and/or their limited
anthelmintic efficacy. Since the introduction of
tartar emetic in 1918, a number of antimonial as well as non-antimonial preparations have been used for the treatment of
schistosomiasis. In the treatment of
clonorchiasis with
antimony preparations,
gentian violet,
emetine HCl,
chloroquine diphosphate and
dithiazanine iodide, only temporary clinical improvement and negative or reduced egg counts could be achieved, but complete cure was not obtained. Although
Hetol (or
hexachloroparaxylol), prolonged administration of oral
dehydroemetine and only two doses of
niclofolan showed
therapeutic effect on
Clonorchis infection, side effects were observed in most of the treated cases. On the other hand,
bithionol proved to be a
drug of choice for
paragonimiasis. However, the need of multiple doses and the many adverse reactions hampered its use in the field. Recently the newly developed
praziquantel (2-cyclohexylcarbonyl-1,2,3,6,7,11b-hexahydro-4H-pyrazino-[2,1-a]+ ++isoquinolin -4-one,
EMBAY 8440,
Biltricide) proved to be safe and effective against trematodes and appears to be the
drug of choice for
infections due to all species of Schistosoma, Clonorchis sinensis, Opisthorchis viverrini, Paragonimus spp. and Metagonimus yokogawai in man.