Clonorchis sinensis: experimental and clinical studies with praziquantel in Korea

A high degree of prophylactic effect was achieved with a single dose of praziquantel (2-cyclohexylcarbonyl-1,2,3,6,7,11b-hexahydro-4H-pyrazino [2,1-a]isoquinolin-4-one, EMBAY 8440, Biltricide), 600 mg/kg bwt once a day, when given to rats at least one day before the infection. To treat the larvae or immature worms at early stages of infection, the following regimens were recommended: 2 X 50 mg/kg bwt for 5 days (Soh et al. 1980) or 3 X 100 mg/kg bwt for 2 days. By morphological examination, it was found that praziquantel induced chronic degeneration of all organs of the parasite such as vacuolization of secretory granules in the integument, degenerative changes of mitochondria and so on. The vacuoles might fuse with each other, and eventually form a balloon-like structure on the tegumental layer causing disruption.

Among various regimens with different dosages, administration of 3 X 25 mg/kg bwt for 2 days showed the best results with complete cure. 53 cases were treated, 33 receiving a dosage of 3 X 25 mg/kg bwt on a single day and 20 receiving the same dosage on two days; the former achieved 99.4% egg reduction rate and 96.9% complete cure, and the latter dosage resulted in 100% complete cure. Side effects such as epigastric pain, nausea, lassitude and headache were complained of in 4 cases among the 53, but were mild and transient. Clinico-physiological examinations during treatment were within normal limits. Clinical symptoms disappeared within one month after treatment. A similar result was reported by other authors, by one of them in one heavily infected case (EPG 452,633).