Liver fluke infections, drugs used

Hexachloroparaxylene has been used in China and Russia as an antihelminthic drug, principally to treat the liver fluke infections (clonorchiasis due to Clonorchis sinensis, schistosomiasis due to Schistosoma japonicum, and opisthorchiasis due to Opisthorchiidae (1,2). However, other treatments are preferred. It is also used very extensively in the veterinary field in Russia. 

The salicylanilide drugs have been widely used to treat intestinal tapeworm and liver fluke infections in humans and animals. Their use in the treatment of hydatid diseases, schistosomiasis and nematode infections is limited [11]. 

THERAPEUTIC USES Praziquantel is FDA approved for therapy of schistosomiasis and liver fluke infections, but also is used to treat infections with many other trematodes and cestodes. Praziquantel is the drug of choice for schistosomiasis caused by all Schistosoma species. Although dosage regimens vary, a single oral dose of 40 mg/kg or three doses of 20 mg/kg each, given 4-6 hours apart, generally produce cure rates of 70-95% and consistent reductions (>85%) in egg counts. Tablets of 600 mg are available. 

Praziquantel has been successfully used to treat liver fluke (Dicrocoelium den-driticum) and pancreatic fluke (Eurytrema pancreaticum) infections in sheep at an oral dose of 50-70 mg/kg [55,56]. The drug is equally effective against the pancreatic flukes, Eurytrema coelmaticum in cattle and liver flukes, Platynosomum fastosum and F. concinnum in cats [57-59]. 

Nitroxynil is currently used for the treatment of F. hepatica infection in cattle and sheep. The recommended dose of the drug is 10 mg/kg given subcutaneously to get 90-99% elimination of the adult liver flukes its activity against immature flukes is low [33,35]. 

Bithionol (Fig. 7-10) is useful for the treatment of Fasciola hepatica (sheep liver fluke) and Paragonimus westermanii, the lung fluke. It is highly effective. The drug impairs egg formation, uncouples oxidative phosphorylation, and chelates iron, possibly from crucial enzymes. None of these facts has been related to a molecular mechanism, which remains obscure. In any case, it would appear that PQ will likely replace this ftw-dichlorophenol as the drug of choice for these two fluke infections. 

Praziquantel is the drug of first choice for infections caused by the Oriental liver fluke and by the fish tapeworm. Both types of infection are transmitted mainly via the consumption of raw fish. Niclosamide is one of two dmgs of choice for fish tapeworm infections (with praziquantel), but it is not active against Clonorchis sinensis. Albendazole is not effective in fish tapeworm infections but is useful in the pork tapeworm larval stage (cysticercosis). The answer is (E). 

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