 The single dose of praziquantel of 40 mg/kg is effective against opisthorchiasis (and also against schistosomiasis).Despite the efficacy of this compound, the lack of an acquired immunity to infection predisposes humans to reinfections in endemic regions.In addition, under experimental conditions, the short-term treatment of "Opisthorchis viverrini"-infected hamsters with praziquantel (400 mg per kg of live weight) induced a dispersion of parasite antigens, resulting in adverse immunopathological changes as a result of oxidative and nitrative stresses following re-infection with "Opisthorchis viverrini", a process which has been proposed to initiate and/or promote the development of cholangiocarcinoma in humans.