Paragonimiasis: experimental and clinical experience with praziquantel in Korea

The effect of praziquantel (2-cyclohexylcarbonyl-1,2,3,6,7,11b-hexahydro-4H-pyrazino[2,1-a]++ +isoquinolin- 4-one, EMBAY 8440, Biltricide) on the ultrastructure of Paragonimus westermani was investigated in vitro and in vivo. In in vitro experiments, P. westermani was less sensitive to praziquantel. Only very few vacuoles were formed in the tegumental syncytium after incubation in 100 micrograms/ml for 60 min. However, in vivo the parasite was successfully destroyed by praziquantel. In fine structural changes of P. westermani obtained from experimentally infected dogs after treatment, bleb-like structures were formed at the papillae near the two suckers and bubble-like vacuoles and vesicles in the tegumental syncytium were observed along the basement membrane being detached from the circular muscles of the worm. It was also observed that many host cells invaded the exposed muscular layer of the worm after exfoliation of the tegument and the interior of the parasite was heavily damaged by those host cells. In our clinical trials, complete cure was obtained in 10 patients given praziquantel at a dosage of 3 X 25 mg/kg body weight for 3 consecutive days and with a dosage of 3 X 25 mg/kg for 2 consecutive days, 18 (85.7%) of 21 patients were cured. On the other hand, the dosage of 3 X 25 mg/kg on one day cured 15 (71.4%) out of 21 patients. Nine uncured cases were treated again with dosages of 3 X 25 mg/kg for 2 or 3 consecutive days. Only two out of nine failed to be completely cured and a very small number of eggs were detected again in their sputum and faeces.(ABSTRACT TRUNCATED AT 250 WORDS)