Evaluation of selected anthelmintic compounds for activity against Opisthorchis viverrini

In vitro and in vivo experiments were employed in the screening of potential anthelmintic agents against Opisthorchis viverrini infection in hamsters. A few selected groups of compounds tested included those that are commercially available as well as those that are still being tested by various pharmaceutical firms. The compounds tested in the present study were praziquantel, amoscanate, albendazole, flubendazole, metrifonate, metronidazole and benzodiazepine derivatives. Results from both in vitro and in vivo experiments showed that at the dosages employed, praziquantel was the only one that gave complete cure, as judged from faecal egg examination and worm recovery at the time of sacrifice. It was therapeutically effective against different developmental stages of O. viverrini including the metacercariae. Moreover, the drug was also effective as a chemoprophylactic agent when given 6 to 12 hr prior to being exposed to infective metacercariae. Other compounds tested were considerably less active although some might have permanently damaged the fluke reproductive capacity, while others were able to suppress egg-laying capacity only temporarily. Together, results suggests that the ineffectiveness of most agents tested in this study is not related to their inability to attain concentrations high enough to kill or damage the flukes in the biliary system but is most likely due the inherent lack of capacity to kill the flukes.